Merge remote-tracking branch 'stable/linux-5.10.y' into rpi-5.10.y
[platform/kernel/linux-rpi.git] / mm / mmap.c
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * mm/mmap.c
4  *
5  * Written by obz.
6  *
7  * Address space accounting code        <alan@lxorguk.ukuu.org.uk>
8  */
9
10 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
11
12 #include <linux/kernel.h>
13 #include <linux/slab.h>
14 #include <linux/backing-dev.h>
15 #include <linux/mm.h>
16 #include <linux/vmacache.h>
17 #include <linux/shm.h>
18 #include <linux/mman.h>
19 #include <linux/pagemap.h>
20 #include <linux/swap.h>
21 #include <linux/syscalls.h>
22 #include <linux/capability.h>
23 #include <linux/init.h>
24 #include <linux/file.h>
25 #include <linux/fs.h>
26 #include <linux/personality.h>
27 #include <linux/security.h>
28 #include <linux/hugetlb.h>
29 #include <linux/shmem_fs.h>
30 #include <linux/profile.h>
31 #include <linux/export.h>
32 #include <linux/mount.h>
33 #include <linux/mempolicy.h>
34 #include <linux/rmap.h>
35 #include <linux/mmu_notifier.h>
36 #include <linux/mmdebug.h>
37 #include <linux/perf_event.h>
38 #include <linux/audit.h>
39 #include <linux/khugepaged.h>
40 #include <linux/uprobes.h>
41 #include <linux/rbtree_augmented.h>
42 #include <linux/notifier.h>
43 #include <linux/memory.h>
44 #include <linux/printk.h>
45 #include <linux/userfaultfd_k.h>
46 #include <linux/moduleparam.h>
47 #include <linux/pkeys.h>
48 #include <linux/oom.h>
49 #include <linux/sched/mm.h>
50
51 #include <linux/uaccess.h>
52 #include <asm/cacheflush.h>
53 #include <asm/tlb.h>
54 #include <asm/mmu_context.h>
55
56 #define CREATE_TRACE_POINTS
57 #include <trace/events/mmap.h>
58
59 #include "internal.h"
60
61 #ifndef arch_mmap_check
62 #define arch_mmap_check(addr, len, flags)       (0)
63 #endif
64
65 #ifdef CONFIG_HAVE_ARCH_MMAP_RND_BITS
66 const int mmap_rnd_bits_min = CONFIG_ARCH_MMAP_RND_BITS_MIN;
67 const int mmap_rnd_bits_max = CONFIG_ARCH_MMAP_RND_BITS_MAX;
68 int mmap_rnd_bits __read_mostly = CONFIG_ARCH_MMAP_RND_BITS;
69 #endif
70 #ifdef CONFIG_HAVE_ARCH_MMAP_RND_COMPAT_BITS
71 const int mmap_rnd_compat_bits_min = CONFIG_ARCH_MMAP_RND_COMPAT_BITS_MIN;
72 const int mmap_rnd_compat_bits_max = CONFIG_ARCH_MMAP_RND_COMPAT_BITS_MAX;
73 int mmap_rnd_compat_bits __read_mostly = CONFIG_ARCH_MMAP_RND_COMPAT_BITS;
74 #endif
75
76 static bool ignore_rlimit_data;
77 core_param(ignore_rlimit_data, ignore_rlimit_data, bool, 0644);
78
79 static void unmap_region(struct mm_struct *mm,
80                 struct vm_area_struct *vma, struct vm_area_struct *prev,
81                 unsigned long start, unsigned long end);
82
83 /* description of effects of mapping type and prot in current implementation.
84  * this is due to the limited x86 page protection hardware.  The expected
85  * behavior is in parens:
86  *
87  * map_type     prot
88  *              PROT_NONE       PROT_READ       PROT_WRITE      PROT_EXEC
89  * MAP_SHARED   r: (no) no      r: (yes) yes    r: (no) yes     r: (no) yes
90  *              w: (no) no      w: (no) no      w: (yes) yes    w: (no) no
91  *              x: (no) no      x: (no) yes     x: (no) yes     x: (yes) yes
92  *
93  * MAP_PRIVATE  r: (no) no      r: (yes) yes    r: (no) yes     r: (no) yes
94  *              w: (no) no      w: (no) no      w: (copy) copy  w: (no) no
95  *              x: (no) no      x: (no) yes     x: (no) yes     x: (yes) yes
96  */
97 pgprot_t protection_map[16] __ro_after_init = {
98         __P000, __P001, __P010, __P011, __P100, __P101, __P110, __P111,
99         __S000, __S001, __S010, __S011, __S100, __S101, __S110, __S111
100 };
101
102 #ifndef CONFIG_ARCH_HAS_FILTER_PGPROT
103 static inline pgprot_t arch_filter_pgprot(pgprot_t prot)
104 {
105         return prot;
106 }
107 #endif
108
109 pgprot_t vm_get_page_prot(unsigned long vm_flags)
110 {
111         pgprot_t ret = __pgprot(pgprot_val(protection_map[vm_flags &
112                                 (VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)]) |
113                         pgprot_val(arch_vm_get_page_prot(vm_flags)));
114
115         return arch_filter_pgprot(ret);
116 }
117 EXPORT_SYMBOL(vm_get_page_prot);
118
119 static pgprot_t vm_pgprot_modify(pgprot_t oldprot, unsigned long vm_flags)
120 {
121         return pgprot_modify(oldprot, vm_get_page_prot(vm_flags));
122 }
123
124 /* Update vma->vm_page_prot to reflect vma->vm_flags. */
125 void vma_set_page_prot(struct vm_area_struct *vma)
126 {
127         unsigned long vm_flags = vma->vm_flags;
128         pgprot_t vm_page_prot;
129
130         vm_page_prot = vm_pgprot_modify(vma->vm_page_prot, vm_flags);
131         if (vma_wants_writenotify(vma, vm_page_prot)) {
132                 vm_flags &= ~VM_SHARED;
133                 vm_page_prot = vm_pgprot_modify(vm_page_prot, vm_flags);
134         }
135         /* remove_protection_ptes reads vma->vm_page_prot without mmap_lock */
136         WRITE_ONCE(vma->vm_page_prot, vm_page_prot);
137 }
138
139 /*
140  * Requires inode->i_mapping->i_mmap_rwsem
141  */
142 static void __remove_shared_vm_struct(struct vm_area_struct *vma,
143                 struct file *file, struct address_space *mapping)
144 {
145         if (vma->vm_flags & VM_DENYWRITE)
146                 allow_write_access(file);
147         if (vma->vm_flags & VM_SHARED)
148                 mapping_unmap_writable(mapping);
149
150         flush_dcache_mmap_lock(mapping);
151         vma_interval_tree_remove(vma, &mapping->i_mmap);
152         flush_dcache_mmap_unlock(mapping);
153 }
154
155 /*
156  * Unlink a file-based vm structure from its interval tree, to hide
157  * vma from rmap and vmtruncate before freeing its page tables.
158  */
159 void unlink_file_vma(struct vm_area_struct *vma)
160 {
161         struct file *file = vma->vm_file;
162
163         if (file) {
164                 struct address_space *mapping = file->f_mapping;
165                 i_mmap_lock_write(mapping);
166                 __remove_shared_vm_struct(vma, file, mapping);
167                 i_mmap_unlock_write(mapping);
168         }
169 }
170
171 /*
172  * Close a vm structure and free it, returning the next.
173  */
174 static struct vm_area_struct *remove_vma(struct vm_area_struct *vma)
175 {
176         struct vm_area_struct *next = vma->vm_next;
177
178         might_sleep();
179         if (vma->vm_ops && vma->vm_ops->close)
180                 vma->vm_ops->close(vma);
181         if (vma->vm_file)
182                 fput(vma->vm_file);
183         mpol_put(vma_policy(vma));
184         vm_area_free(vma);
185         return next;
186 }
187
188 static int do_brk_flags(unsigned long addr, unsigned long request, unsigned long flags,
189                 struct list_head *uf);
190 SYSCALL_DEFINE1(brk, unsigned long, brk)
191 {
192         unsigned long retval;
193         unsigned long newbrk, oldbrk, origbrk;
194         struct mm_struct *mm = current->mm;
195         struct vm_area_struct *next;
196         unsigned long min_brk;
197         bool populate;
198         bool downgraded = false;
199         LIST_HEAD(uf);
200
201         if (mmap_write_lock_killable(mm))
202                 return -EINTR;
203
204         origbrk = mm->brk;
205
206 #ifdef CONFIG_COMPAT_BRK
207         /*
208          * CONFIG_COMPAT_BRK can still be overridden by setting
209          * randomize_va_space to 2, which will still cause mm->start_brk
210          * to be arbitrarily shifted
211          */
212         if (current->brk_randomized)
213                 min_brk = mm->start_brk;
214         else
215                 min_brk = mm->end_data;
216 #else
217         min_brk = mm->start_brk;
218 #endif
219         if (brk < min_brk)
220                 goto out;
221
222         /*
223          * Check against rlimit here. If this check is done later after the test
224          * of oldbrk with newbrk then it can escape the test and let the data
225          * segment grow beyond its set limit the in case where the limit is
226          * not page aligned -Ram Gupta
227          */
228         if (check_data_rlimit(rlimit(RLIMIT_DATA), brk, mm->start_brk,
229                               mm->end_data, mm->start_data))
230                 goto out;
231
232         newbrk = PAGE_ALIGN(brk);
233         oldbrk = PAGE_ALIGN(mm->brk);
234         if (oldbrk == newbrk) {
235                 mm->brk = brk;
236                 goto success;
237         }
238
239         /*
240          * Always allow shrinking brk.
241          * __do_munmap() may downgrade mmap_lock to read.
242          */
243         if (brk <= mm->brk) {
244                 int ret;
245
246                 /*
247                  * mm->brk must to be protected by write mmap_lock so update it
248                  * before downgrading mmap_lock. When __do_munmap() fails,
249                  * mm->brk will be restored from origbrk.
250                  */
251                 mm->brk = brk;
252                 ret = __do_munmap(mm, newbrk, oldbrk-newbrk, &uf, true);
253                 if (ret < 0) {
254                         mm->brk = origbrk;
255                         goto out;
256                 } else if (ret == 1) {
257                         downgraded = true;
258                 }
259                 goto success;
260         }
261
262         /* Check against existing mmap mappings. */
263         next = find_vma(mm, oldbrk);
264         if (next && newbrk + PAGE_SIZE > vm_start_gap(next))
265                 goto out;
266
267         /* Ok, looks good - let it rip. */
268         if (do_brk_flags(oldbrk, newbrk-oldbrk, 0, &uf) < 0)
269                 goto out;
270         mm->brk = brk;
271
272 success:
273         populate = newbrk > oldbrk && (mm->def_flags & VM_LOCKED) != 0;
274         if (downgraded)
275                 mmap_read_unlock(mm);
276         else
277                 mmap_write_unlock(mm);
278         userfaultfd_unmap_complete(mm, &uf);
279         if (populate)
280                 mm_populate(oldbrk, newbrk - oldbrk);
281         return brk;
282
283 out:
284         retval = origbrk;
285         mmap_write_unlock(mm);
286         return retval;
287 }
288
289 static inline unsigned long vma_compute_gap(struct vm_area_struct *vma)
290 {
291         unsigned long gap, prev_end;
292
293         /*
294          * Note: in the rare case of a VM_GROWSDOWN above a VM_GROWSUP, we
295          * allow two stack_guard_gaps between them here, and when choosing
296          * an unmapped area; whereas when expanding we only require one.
297          * That's a little inconsistent, but keeps the code here simpler.
298          */
299         gap = vm_start_gap(vma);
300         if (vma->vm_prev) {
301                 prev_end = vm_end_gap(vma->vm_prev);
302                 if (gap > prev_end)
303                         gap -= prev_end;
304                 else
305                         gap = 0;
306         }
307         return gap;
308 }
309
310 #ifdef CONFIG_DEBUG_VM_RB
311 static unsigned long vma_compute_subtree_gap(struct vm_area_struct *vma)
312 {
313         unsigned long max = vma_compute_gap(vma), subtree_gap;
314         if (vma->vm_rb.rb_left) {
315                 subtree_gap = rb_entry(vma->vm_rb.rb_left,
316                                 struct vm_area_struct, vm_rb)->rb_subtree_gap;
317                 if (subtree_gap > max)
318                         max = subtree_gap;
319         }
320         if (vma->vm_rb.rb_right) {
321                 subtree_gap = rb_entry(vma->vm_rb.rb_right,
322                                 struct vm_area_struct, vm_rb)->rb_subtree_gap;
323                 if (subtree_gap > max)
324                         max = subtree_gap;
325         }
326         return max;
327 }
328
329 static int browse_rb(struct mm_struct *mm)
330 {
331         struct rb_root *root = &mm->mm_rb;
332         int i = 0, j, bug = 0;
333         struct rb_node *nd, *pn = NULL;
334         unsigned long prev = 0, pend = 0;
335
336         for (nd = rb_first(root); nd; nd = rb_next(nd)) {
337                 struct vm_area_struct *vma;
338                 vma = rb_entry(nd, struct vm_area_struct, vm_rb);
339                 if (vma->vm_start < prev) {
340                         pr_emerg("vm_start %lx < prev %lx\n",
341                                   vma->vm_start, prev);
342                         bug = 1;
343                 }
344                 if (vma->vm_start < pend) {
345                         pr_emerg("vm_start %lx < pend %lx\n",
346                                   vma->vm_start, pend);
347                         bug = 1;
348                 }
349                 if (vma->vm_start > vma->vm_end) {
350                         pr_emerg("vm_start %lx > vm_end %lx\n",
351                                   vma->vm_start, vma->vm_end);
352                         bug = 1;
353                 }
354                 spin_lock(&mm->page_table_lock);
355                 if (vma->rb_subtree_gap != vma_compute_subtree_gap(vma)) {
356                         pr_emerg("free gap %lx, correct %lx\n",
357                                vma->rb_subtree_gap,
358                                vma_compute_subtree_gap(vma));
359                         bug = 1;
360                 }
361                 spin_unlock(&mm->page_table_lock);
362                 i++;
363                 pn = nd;
364                 prev = vma->vm_start;
365                 pend = vma->vm_end;
366         }
367         j = 0;
368         for (nd = pn; nd; nd = rb_prev(nd))
369                 j++;
370         if (i != j) {
371                 pr_emerg("backwards %d, forwards %d\n", j, i);
372                 bug = 1;
373         }
374         return bug ? -1 : i;
375 }
376
377 static void validate_mm_rb(struct rb_root *root, struct vm_area_struct *ignore)
378 {
379         struct rb_node *nd;
380
381         for (nd = rb_first(root); nd; nd = rb_next(nd)) {
382                 struct vm_area_struct *vma;
383                 vma = rb_entry(nd, struct vm_area_struct, vm_rb);
384                 VM_BUG_ON_VMA(vma != ignore &&
385                         vma->rb_subtree_gap != vma_compute_subtree_gap(vma),
386                         vma);
387         }
388 }
389
390 static void validate_mm(struct mm_struct *mm)
391 {
392         int bug = 0;
393         int i = 0;
394         unsigned long highest_address = 0;
395         struct vm_area_struct *vma = mm->mmap;
396
397         while (vma) {
398                 struct anon_vma *anon_vma = vma->anon_vma;
399                 struct anon_vma_chain *avc;
400
401                 if (anon_vma) {
402                         anon_vma_lock_read(anon_vma);
403                         list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
404                                 anon_vma_interval_tree_verify(avc);
405                         anon_vma_unlock_read(anon_vma);
406                 }
407
408                 highest_address = vm_end_gap(vma);
409                 vma = vma->vm_next;
410                 i++;
411         }
412         if (i != mm->map_count) {
413                 pr_emerg("map_count %d vm_next %d\n", mm->map_count, i);
414                 bug = 1;
415         }
416         if (highest_address != mm->highest_vm_end) {
417                 pr_emerg("mm->highest_vm_end %lx, found %lx\n",
418                           mm->highest_vm_end, highest_address);
419                 bug = 1;
420         }
421         i = browse_rb(mm);
422         if (i != mm->map_count) {
423                 if (i != -1)
424                         pr_emerg("map_count %d rb %d\n", mm->map_count, i);
425                 bug = 1;
426         }
427         VM_BUG_ON_MM(bug, mm);
428 }
429 #else
430 #define validate_mm_rb(root, ignore) do { } while (0)
431 #define validate_mm(mm) do { } while (0)
432 #endif
433
434 RB_DECLARE_CALLBACKS_MAX(static, vma_gap_callbacks,
435                          struct vm_area_struct, vm_rb,
436                          unsigned long, rb_subtree_gap, vma_compute_gap)
437
438 /*
439  * Update augmented rbtree rb_subtree_gap values after vma->vm_start or
440  * vma->vm_prev->vm_end values changed, without modifying the vma's position
441  * in the rbtree.
442  */
443 static void vma_gap_update(struct vm_area_struct *vma)
444 {
445         /*
446          * As it turns out, RB_DECLARE_CALLBACKS_MAX() already created
447          * a callback function that does exactly what we want.
448          */
449         vma_gap_callbacks_propagate(&vma->vm_rb, NULL);
450 }
451
452 static inline void vma_rb_insert(struct vm_area_struct *vma,
453                                  struct rb_root *root)
454 {
455         /* All rb_subtree_gap values must be consistent prior to insertion */
456         validate_mm_rb(root, NULL);
457
458         rb_insert_augmented(&vma->vm_rb, root, &vma_gap_callbacks);
459 }
460
461 static void __vma_rb_erase(struct vm_area_struct *vma, struct rb_root *root)
462 {
463         /*
464          * Note rb_erase_augmented is a fairly large inline function,
465          * so make sure we instantiate it only once with our desired
466          * augmented rbtree callbacks.
467          */
468         rb_erase_augmented(&vma->vm_rb, root, &vma_gap_callbacks);
469 }
470
471 static __always_inline void vma_rb_erase_ignore(struct vm_area_struct *vma,
472                                                 struct rb_root *root,
473                                                 struct vm_area_struct *ignore)
474 {
475         /*
476          * All rb_subtree_gap values must be consistent prior to erase,
477          * with the possible exception of
478          *
479          * a. the "next" vma being erased if next->vm_start was reduced in
480          *    __vma_adjust() -> __vma_unlink()
481          * b. the vma being erased in detach_vmas_to_be_unmapped() ->
482          *    vma_rb_erase()
483          */
484         validate_mm_rb(root, ignore);
485
486         __vma_rb_erase(vma, root);
487 }
488
489 static __always_inline void vma_rb_erase(struct vm_area_struct *vma,
490                                          struct rb_root *root)
491 {
492         vma_rb_erase_ignore(vma, root, vma);
493 }
494
495 /*
496  * vma has some anon_vma assigned, and is already inserted on that
497  * anon_vma's interval trees.
498  *
499  * Before updating the vma's vm_start / vm_end / vm_pgoff fields, the
500  * vma must be removed from the anon_vma's interval trees using
501  * anon_vma_interval_tree_pre_update_vma().
502  *
503  * After the update, the vma will be reinserted using
504  * anon_vma_interval_tree_post_update_vma().
505  *
506  * The entire update must be protected by exclusive mmap_lock and by
507  * the root anon_vma's mutex.
508  */
509 static inline void
510 anon_vma_interval_tree_pre_update_vma(struct vm_area_struct *vma)
511 {
512         struct anon_vma_chain *avc;
513
514         list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
515                 anon_vma_interval_tree_remove(avc, &avc->anon_vma->rb_root);
516 }
517
518 static inline void
519 anon_vma_interval_tree_post_update_vma(struct vm_area_struct *vma)
520 {
521         struct anon_vma_chain *avc;
522
523         list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
524                 anon_vma_interval_tree_insert(avc, &avc->anon_vma->rb_root);
525 }
526
527 static int find_vma_links(struct mm_struct *mm, unsigned long addr,
528                 unsigned long end, struct vm_area_struct **pprev,
529                 struct rb_node ***rb_link, struct rb_node **rb_parent)
530 {
531         struct rb_node **__rb_link, *__rb_parent, *rb_prev;
532
533         __rb_link = &mm->mm_rb.rb_node;
534         rb_prev = __rb_parent = NULL;
535
536         while (*__rb_link) {
537                 struct vm_area_struct *vma_tmp;
538
539                 __rb_parent = *__rb_link;
540                 vma_tmp = rb_entry(__rb_parent, struct vm_area_struct, vm_rb);
541
542                 if (vma_tmp->vm_end > addr) {
543                         /* Fail if an existing vma overlaps the area */
544                         if (vma_tmp->vm_start < end)
545                                 return -ENOMEM;
546                         __rb_link = &__rb_parent->rb_left;
547                 } else {
548                         rb_prev = __rb_parent;
549                         __rb_link = &__rb_parent->rb_right;
550                 }
551         }
552
553         *pprev = NULL;
554         if (rb_prev)
555                 *pprev = rb_entry(rb_prev, struct vm_area_struct, vm_rb);
556         *rb_link = __rb_link;
557         *rb_parent = __rb_parent;
558         return 0;
559 }
560
561 /*
562  * vma_next() - Get the next VMA.
563  * @mm: The mm_struct.
564  * @vma: The current vma.
565  *
566  * If @vma is NULL, return the first vma in the mm.
567  *
568  * Returns: The next VMA after @vma.
569  */
570 static inline struct vm_area_struct *vma_next(struct mm_struct *mm,
571                                          struct vm_area_struct *vma)
572 {
573         if (!vma)
574                 return mm->mmap;
575
576         return vma->vm_next;
577 }
578
579 /*
580  * munmap_vma_range() - munmap VMAs that overlap a range.
581  * @mm: The mm struct
582  * @start: The start of the range.
583  * @len: The length of the range.
584  * @pprev: pointer to the pointer that will be set to previous vm_area_struct
585  * @rb_link: the rb_node
586  * @rb_parent: the parent rb_node
587  *
588  * Find all the vm_area_struct that overlap from @start to
589  * @end and munmap them.  Set @pprev to the previous vm_area_struct.
590  *
591  * Returns: -ENOMEM on munmap failure or 0 on success.
592  */
593 static inline int
594 munmap_vma_range(struct mm_struct *mm, unsigned long start, unsigned long len,
595                  struct vm_area_struct **pprev, struct rb_node ***link,
596                  struct rb_node **parent, struct list_head *uf)
597 {
598
599         while (find_vma_links(mm, start, start + len, pprev, link, parent))
600                 if (do_munmap(mm, start, len, uf))
601                         return -ENOMEM;
602
603         return 0;
604 }
605 static unsigned long count_vma_pages_range(struct mm_struct *mm,
606                 unsigned long addr, unsigned long end)
607 {
608         unsigned long nr_pages = 0;
609         struct vm_area_struct *vma;
610
611         /* Find first overlaping mapping */
612         vma = find_vma_intersection(mm, addr, end);
613         if (!vma)
614                 return 0;
615
616         nr_pages = (min(end, vma->vm_end) -
617                 max(addr, vma->vm_start)) >> PAGE_SHIFT;
618
619         /* Iterate over the rest of the overlaps */
620         for (vma = vma->vm_next; vma; vma = vma->vm_next) {
621                 unsigned long overlap_len;
622
623                 if (vma->vm_start > end)
624                         break;
625
626                 overlap_len = min(end, vma->vm_end) - vma->vm_start;
627                 nr_pages += overlap_len >> PAGE_SHIFT;
628         }
629
630         return nr_pages;
631 }
632
633 void __vma_link_rb(struct mm_struct *mm, struct vm_area_struct *vma,
634                 struct rb_node **rb_link, struct rb_node *rb_parent)
635 {
636         /* Update tracking information for the gap following the new vma. */
637         if (vma->vm_next)
638                 vma_gap_update(vma->vm_next);
639         else
640                 mm->highest_vm_end = vm_end_gap(vma);
641
642         /*
643          * vma->vm_prev wasn't known when we followed the rbtree to find the
644          * correct insertion point for that vma. As a result, we could not
645          * update the vma vm_rb parents rb_subtree_gap values on the way down.
646          * So, we first insert the vma with a zero rb_subtree_gap value
647          * (to be consistent with what we did on the way down), and then
648          * immediately update the gap to the correct value. Finally we
649          * rebalance the rbtree after all augmented values have been set.
650          */
651         rb_link_node(&vma->vm_rb, rb_parent, rb_link);
652         vma->rb_subtree_gap = 0;
653         vma_gap_update(vma);
654         vma_rb_insert(vma, &mm->mm_rb);
655 }
656
657 static void __vma_link_file(struct vm_area_struct *vma)
658 {
659         struct file *file;
660
661         file = vma->vm_file;
662         if (file) {
663                 struct address_space *mapping = file->f_mapping;
664
665                 if (vma->vm_flags & VM_DENYWRITE)
666                         put_write_access(file_inode(file));
667                 if (vma->vm_flags & VM_SHARED)
668                         mapping_allow_writable(mapping);
669
670                 flush_dcache_mmap_lock(mapping);
671                 vma_interval_tree_insert(vma, &mapping->i_mmap);
672                 flush_dcache_mmap_unlock(mapping);
673         }
674 }
675
676 static void
677 __vma_link(struct mm_struct *mm, struct vm_area_struct *vma,
678         struct vm_area_struct *prev, struct rb_node **rb_link,
679         struct rb_node *rb_parent)
680 {
681         __vma_link_list(mm, vma, prev);
682         __vma_link_rb(mm, vma, rb_link, rb_parent);
683 }
684
685 static void vma_link(struct mm_struct *mm, struct vm_area_struct *vma,
686                         struct vm_area_struct *prev, struct rb_node **rb_link,
687                         struct rb_node *rb_parent)
688 {
689         struct address_space *mapping = NULL;
690
691         if (vma->vm_file) {
692                 mapping = vma->vm_file->f_mapping;
693                 i_mmap_lock_write(mapping);
694         }
695
696         __vma_link(mm, vma, prev, rb_link, rb_parent);
697         __vma_link_file(vma);
698
699         if (mapping)
700                 i_mmap_unlock_write(mapping);
701
702         mm->map_count++;
703         validate_mm(mm);
704 }
705
706 /*
707  * Helper for vma_adjust() in the split_vma insert case: insert a vma into the
708  * mm's list and rbtree.  It has already been inserted into the interval tree.
709  */
710 static void __insert_vm_struct(struct mm_struct *mm, struct vm_area_struct *vma)
711 {
712         struct vm_area_struct *prev;
713         struct rb_node **rb_link, *rb_parent;
714
715         if (find_vma_links(mm, vma->vm_start, vma->vm_end,
716                            &prev, &rb_link, &rb_parent))
717                 BUG();
718         __vma_link(mm, vma, prev, rb_link, rb_parent);
719         mm->map_count++;
720 }
721
722 static __always_inline void __vma_unlink(struct mm_struct *mm,
723                                                 struct vm_area_struct *vma,
724                                                 struct vm_area_struct *ignore)
725 {
726         vma_rb_erase_ignore(vma, &mm->mm_rb, ignore);
727         __vma_unlink_list(mm, vma);
728         /* Kill the cache */
729         vmacache_invalidate(mm);
730 }
731
732 /*
733  * We cannot adjust vm_start, vm_end, vm_pgoff fields of a vma that
734  * is already present in an i_mmap tree without adjusting the tree.
735  * The following helper function should be used when such adjustments
736  * are necessary.  The "insert" vma (if any) is to be inserted
737  * before we drop the necessary locks.
738  */
739 int __vma_adjust(struct vm_area_struct *vma, unsigned long start,
740         unsigned long end, pgoff_t pgoff, struct vm_area_struct *insert,
741         struct vm_area_struct *expand)
742 {
743         struct mm_struct *mm = vma->vm_mm;
744         struct vm_area_struct *next = vma->vm_next, *orig_vma = vma;
745         struct address_space *mapping = NULL;
746         struct rb_root_cached *root = NULL;
747         struct anon_vma *anon_vma = NULL;
748         struct file *file = vma->vm_file;
749         bool start_changed = false, end_changed = false;
750         long adjust_next = 0;
751         int remove_next = 0;
752
753         if (next && !insert) {
754                 struct vm_area_struct *exporter = NULL, *importer = NULL;
755
756                 if (end >= next->vm_end) {
757                         /*
758                          * vma expands, overlapping all the next, and
759                          * perhaps the one after too (mprotect case 6).
760                          * The only other cases that gets here are
761                          * case 1, case 7 and case 8.
762                          */
763                         if (next == expand) {
764                                 /*
765                                  * The only case where we don't expand "vma"
766                                  * and we expand "next" instead is case 8.
767                                  */
768                                 VM_WARN_ON(end != next->vm_end);
769                                 /*
770                                  * remove_next == 3 means we're
771                                  * removing "vma" and that to do so we
772                                  * swapped "vma" and "next".
773                                  */
774                                 remove_next = 3;
775                                 VM_WARN_ON(file != next->vm_file);
776                                 swap(vma, next);
777                         } else {
778                                 VM_WARN_ON(expand != vma);
779                                 /*
780                                  * case 1, 6, 7, remove_next == 2 is case 6,
781                                  * remove_next == 1 is case 1 or 7.
782                                  */
783                                 remove_next = 1 + (end > next->vm_end);
784                                 VM_WARN_ON(remove_next == 2 &&
785                                            end != next->vm_next->vm_end);
786                                 /* trim end to next, for case 6 first pass */
787                                 end = next->vm_end;
788                         }
789
790                         exporter = next;
791                         importer = vma;
792
793                         /*
794                          * If next doesn't have anon_vma, import from vma after
795                          * next, if the vma overlaps with it.
796                          */
797                         if (remove_next == 2 && !next->anon_vma)
798                                 exporter = next->vm_next;
799
800                 } else if (end > next->vm_start) {
801                         /*
802                          * vma expands, overlapping part of the next:
803                          * mprotect case 5 shifting the boundary up.
804                          */
805                         adjust_next = (end - next->vm_start);
806                         exporter = next;
807                         importer = vma;
808                         VM_WARN_ON(expand != importer);
809                 } else if (end < vma->vm_end) {
810                         /*
811                          * vma shrinks, and !insert tells it's not
812                          * split_vma inserting another: so it must be
813                          * mprotect case 4 shifting the boundary down.
814                          */
815                         adjust_next = -(vma->vm_end - end);
816                         exporter = vma;
817                         importer = next;
818                         VM_WARN_ON(expand != importer);
819                 }
820
821                 /*
822                  * Easily overlooked: when mprotect shifts the boundary,
823                  * make sure the expanding vma has anon_vma set if the
824                  * shrinking vma had, to cover any anon pages imported.
825                  */
826                 if (exporter && exporter->anon_vma && !importer->anon_vma) {
827                         int error;
828
829                         importer->anon_vma = exporter->anon_vma;
830                         error = anon_vma_clone(importer, exporter);
831                         if (error)
832                                 return error;
833                 }
834         }
835 again:
836         vma_adjust_trans_huge(orig_vma, start, end, adjust_next);
837
838         if (file) {
839                 mapping = file->f_mapping;
840                 root = &mapping->i_mmap;
841                 uprobe_munmap(vma, vma->vm_start, vma->vm_end);
842
843                 if (adjust_next)
844                         uprobe_munmap(next, next->vm_start, next->vm_end);
845
846                 i_mmap_lock_write(mapping);
847                 if (insert) {
848                         /*
849                          * Put into interval tree now, so instantiated pages
850                          * are visible to arm/parisc __flush_dcache_page
851                          * throughout; but we cannot insert into address
852                          * space until vma start or end is updated.
853                          */
854                         __vma_link_file(insert);
855                 }
856         }
857
858         anon_vma = vma->anon_vma;
859         if (!anon_vma && adjust_next)
860                 anon_vma = next->anon_vma;
861         if (anon_vma) {
862                 VM_WARN_ON(adjust_next && next->anon_vma &&
863                            anon_vma != next->anon_vma);
864                 anon_vma_lock_write(anon_vma);
865                 anon_vma_interval_tree_pre_update_vma(vma);
866                 if (adjust_next)
867                         anon_vma_interval_tree_pre_update_vma(next);
868         }
869
870         if (file) {
871                 flush_dcache_mmap_lock(mapping);
872                 vma_interval_tree_remove(vma, root);
873                 if (adjust_next)
874                         vma_interval_tree_remove(next, root);
875         }
876
877         if (start != vma->vm_start) {
878                 vma->vm_start = start;
879                 start_changed = true;
880         }
881         if (end != vma->vm_end) {
882                 vma->vm_end = end;
883                 end_changed = true;
884         }
885         vma->vm_pgoff = pgoff;
886         if (adjust_next) {
887                 next->vm_start += adjust_next;
888                 next->vm_pgoff += adjust_next >> PAGE_SHIFT;
889         }
890
891         if (file) {
892                 if (adjust_next)
893                         vma_interval_tree_insert(next, root);
894                 vma_interval_tree_insert(vma, root);
895                 flush_dcache_mmap_unlock(mapping);
896         }
897
898         if (remove_next) {
899                 /*
900                  * vma_merge has merged next into vma, and needs
901                  * us to remove next before dropping the locks.
902                  */
903                 if (remove_next != 3)
904                         __vma_unlink(mm, next, next);
905                 else
906                         /*
907                          * vma is not before next if they've been
908                          * swapped.
909                          *
910                          * pre-swap() next->vm_start was reduced so
911                          * tell validate_mm_rb to ignore pre-swap()
912                          * "next" (which is stored in post-swap()
913                          * "vma").
914                          */
915                         __vma_unlink(mm, next, vma);
916                 if (file)
917                         __remove_shared_vm_struct(next, file, mapping);
918         } else if (insert) {
919                 /*
920                  * split_vma has split insert from vma, and needs
921                  * us to insert it before dropping the locks
922                  * (it may either follow vma or precede it).
923                  */
924                 __insert_vm_struct(mm, insert);
925         } else {
926                 if (start_changed)
927                         vma_gap_update(vma);
928                 if (end_changed) {
929                         if (!next)
930                                 mm->highest_vm_end = vm_end_gap(vma);
931                         else if (!adjust_next)
932                                 vma_gap_update(next);
933                 }
934         }
935
936         if (anon_vma) {
937                 anon_vma_interval_tree_post_update_vma(vma);
938                 if (adjust_next)
939                         anon_vma_interval_tree_post_update_vma(next);
940                 anon_vma_unlock_write(anon_vma);
941         }
942
943         if (file) {
944                 i_mmap_unlock_write(mapping);
945                 uprobe_mmap(vma);
946
947                 if (adjust_next)
948                         uprobe_mmap(next);
949         }
950
951         if (remove_next) {
952                 if (file) {
953                         uprobe_munmap(next, next->vm_start, next->vm_end);
954                         fput(file);
955                 }
956                 if (next->anon_vma)
957                         anon_vma_merge(vma, next);
958                 mm->map_count--;
959                 mpol_put(vma_policy(next));
960                 vm_area_free(next);
961                 /*
962                  * In mprotect's case 6 (see comments on vma_merge),
963                  * we must remove another next too. It would clutter
964                  * up the code too much to do both in one go.
965                  */
966                 if (remove_next != 3) {
967                         /*
968                          * If "next" was removed and vma->vm_end was
969                          * expanded (up) over it, in turn
970                          * "next->vm_prev->vm_end" changed and the
971                          * "vma->vm_next" gap must be updated.
972                          */
973                         next = vma->vm_next;
974                 } else {
975                         /*
976                          * For the scope of the comment "next" and
977                          * "vma" considered pre-swap(): if "vma" was
978                          * removed, next->vm_start was expanded (down)
979                          * over it and the "next" gap must be updated.
980                          * Because of the swap() the post-swap() "vma"
981                          * actually points to pre-swap() "next"
982                          * (post-swap() "next" as opposed is now a
983                          * dangling pointer).
984                          */
985                         next = vma;
986                 }
987                 if (remove_next == 2) {
988                         remove_next = 1;
989                         end = next->vm_end;
990                         goto again;
991                 }
992                 else if (next)
993                         vma_gap_update(next);
994                 else {
995                         /*
996                          * If remove_next == 2 we obviously can't
997                          * reach this path.
998                          *
999                          * If remove_next == 3 we can't reach this
1000                          * path because pre-swap() next is always not
1001                          * NULL. pre-swap() "next" is not being
1002                          * removed and its next->vm_end is not altered
1003                          * (and furthermore "end" already matches
1004                          * next->vm_end in remove_next == 3).
1005                          *
1006                          * We reach this only in the remove_next == 1
1007                          * case if the "next" vma that was removed was
1008                          * the highest vma of the mm. However in such
1009                          * case next->vm_end == "end" and the extended
1010                          * "vma" has vma->vm_end == next->vm_end so
1011                          * mm->highest_vm_end doesn't need any update
1012                          * in remove_next == 1 case.
1013                          */
1014                         VM_WARN_ON(mm->highest_vm_end != vm_end_gap(vma));
1015                 }
1016         }
1017         if (insert && file)
1018                 uprobe_mmap(insert);
1019
1020         validate_mm(mm);
1021
1022         return 0;
1023 }
1024
1025 /*
1026  * If the vma has a ->close operation then the driver probably needs to release
1027  * per-vma resources, so we don't attempt to merge those.
1028  */
1029 static inline int is_mergeable_vma(struct vm_area_struct *vma,
1030                                 struct file *file, unsigned long vm_flags,
1031                                 struct vm_userfaultfd_ctx vm_userfaultfd_ctx)
1032 {
1033         /*
1034          * VM_SOFTDIRTY should not prevent from VMA merging, if we
1035          * match the flags but dirty bit -- the caller should mark
1036          * merged VMA as dirty. If dirty bit won't be excluded from
1037          * comparison, we increase pressure on the memory system forcing
1038          * the kernel to generate new VMAs when old one could be
1039          * extended instead.
1040          */
1041         if ((vma->vm_flags ^ vm_flags) & ~VM_SOFTDIRTY)
1042                 return 0;
1043         if (vma->vm_file != file)
1044                 return 0;
1045         if (vma->vm_ops && vma->vm_ops->close)
1046                 return 0;
1047         if (!is_mergeable_vm_userfaultfd_ctx(vma, vm_userfaultfd_ctx))
1048                 return 0;
1049         return 1;
1050 }
1051
1052 static inline int is_mergeable_anon_vma(struct anon_vma *anon_vma1,
1053                                         struct anon_vma *anon_vma2,
1054                                         struct vm_area_struct *vma)
1055 {
1056         /*
1057          * The list_is_singular() test is to avoid merging VMA cloned from
1058          * parents. This can improve scalability caused by anon_vma lock.
1059          */
1060         if ((!anon_vma1 || !anon_vma2) && (!vma ||
1061                 list_is_singular(&vma->anon_vma_chain)))
1062                 return 1;
1063         return anon_vma1 == anon_vma2;
1064 }
1065
1066 /*
1067  * Return true if we can merge this (vm_flags,anon_vma,file,vm_pgoff)
1068  * in front of (at a lower virtual address and file offset than) the vma.
1069  *
1070  * We cannot merge two vmas if they have differently assigned (non-NULL)
1071  * anon_vmas, nor if same anon_vma is assigned but offsets incompatible.
1072  *
1073  * We don't check here for the merged mmap wrapping around the end of pagecache
1074  * indices (16TB on ia32) because do_mmap() does not permit mmap's which
1075  * wrap, nor mmaps which cover the final page at index -1UL.
1076  */
1077 static int
1078 can_vma_merge_before(struct vm_area_struct *vma, unsigned long vm_flags,
1079                      struct anon_vma *anon_vma, struct file *file,
1080                      pgoff_t vm_pgoff,
1081                      struct vm_userfaultfd_ctx vm_userfaultfd_ctx)
1082 {
1083         if (is_mergeable_vma(vma, file, vm_flags, vm_userfaultfd_ctx) &&
1084             is_mergeable_anon_vma(anon_vma, vma->anon_vma, vma)) {
1085                 if (vma->vm_pgoff == vm_pgoff)
1086                         return 1;
1087         }
1088         return 0;
1089 }
1090
1091 /*
1092  * Return true if we can merge this (vm_flags,anon_vma,file,vm_pgoff)
1093  * beyond (at a higher virtual address and file offset than) the vma.
1094  *
1095  * We cannot merge two vmas if they have differently assigned (non-NULL)
1096  * anon_vmas, nor if same anon_vma is assigned but offsets incompatible.
1097  */
1098 static int
1099 can_vma_merge_after(struct vm_area_struct *vma, unsigned long vm_flags,
1100                     struct anon_vma *anon_vma, struct file *file,
1101                     pgoff_t vm_pgoff,
1102                     struct vm_userfaultfd_ctx vm_userfaultfd_ctx)
1103 {
1104         if (is_mergeable_vma(vma, file, vm_flags, vm_userfaultfd_ctx) &&
1105             is_mergeable_anon_vma(anon_vma, vma->anon_vma, vma)) {
1106                 pgoff_t vm_pglen;
1107                 vm_pglen = vma_pages(vma);
1108                 if (vma->vm_pgoff + vm_pglen == vm_pgoff)
1109                         return 1;
1110         }
1111         return 0;
1112 }
1113
1114 /*
1115  * Given a mapping request (addr,end,vm_flags,file,pgoff), figure out
1116  * whether that can be merged with its predecessor or its successor.
1117  * Or both (it neatly fills a hole).
1118  *
1119  * In most cases - when called for mmap, brk or mremap - [addr,end) is
1120  * certain not to be mapped by the time vma_merge is called; but when
1121  * called for mprotect, it is certain to be already mapped (either at
1122  * an offset within prev, or at the start of next), and the flags of
1123  * this area are about to be changed to vm_flags - and the no-change
1124  * case has already been eliminated.
1125  *
1126  * The following mprotect cases have to be considered, where AAAA is
1127  * the area passed down from mprotect_fixup, never extending beyond one
1128  * vma, PPPPPP is the prev vma specified, and NNNNNN the next vma after:
1129  *
1130  *     AAAA             AAAA                   AAAA
1131  *    PPPPPPNNNNNN    PPPPPPNNNNNN       PPPPPPNNNNNN
1132  *    cannot merge    might become       might become
1133  *                    PPNNNNNNNNNN       PPPPPPPPPPNN
1134  *    mmap, brk or    case 4 below       case 5 below
1135  *    mremap move:
1136  *                        AAAA               AAAA
1137  *                    PPPP    NNNN       PPPPNNNNXXXX
1138  *                    might become       might become
1139  *                    PPPPPPPPPPPP 1 or  PPPPPPPPPPPP 6 or
1140  *                    PPPPPPPPNNNN 2 or  PPPPPPPPXXXX 7 or
1141  *                    PPPPNNNNNNNN 3     PPPPXXXXXXXX 8
1142  *
1143  * It is important for case 8 that the vma NNNN overlapping the
1144  * region AAAA is never going to extended over XXXX. Instead XXXX must
1145  * be extended in region AAAA and NNNN must be removed. This way in
1146  * all cases where vma_merge succeeds, the moment vma_adjust drops the
1147  * rmap_locks, the properties of the merged vma will be already
1148  * correct for the whole merged range. Some of those properties like
1149  * vm_page_prot/vm_flags may be accessed by rmap_walks and they must
1150  * be correct for the whole merged range immediately after the
1151  * rmap_locks are released. Otherwise if XXXX would be removed and
1152  * NNNN would be extended over the XXXX range, remove_migration_ptes
1153  * or other rmap walkers (if working on addresses beyond the "end"
1154  * parameter) may establish ptes with the wrong permissions of NNNN
1155  * instead of the right permissions of XXXX.
1156  */
1157 struct vm_area_struct *vma_merge(struct mm_struct *mm,
1158                         struct vm_area_struct *prev, unsigned long addr,
1159                         unsigned long end, unsigned long vm_flags,
1160                         struct anon_vma *anon_vma, struct file *file,
1161                         pgoff_t pgoff, struct mempolicy *policy,
1162                         struct vm_userfaultfd_ctx vm_userfaultfd_ctx)
1163 {
1164         pgoff_t pglen = (end - addr) >> PAGE_SHIFT;
1165         struct vm_area_struct *area, *next;
1166         int err;
1167
1168         /*
1169          * We later require that vma->vm_flags == vm_flags,
1170          * so this tests vma->vm_flags & VM_SPECIAL, too.
1171          */
1172         if (vm_flags & VM_SPECIAL)
1173                 return NULL;
1174
1175         next = vma_next(mm, prev);
1176         area = next;
1177         if (area && area->vm_end == end)                /* cases 6, 7, 8 */
1178                 next = next->vm_next;
1179
1180         /* verify some invariant that must be enforced by the caller */
1181         VM_WARN_ON(prev && addr <= prev->vm_start);
1182         VM_WARN_ON(area && end > area->vm_end);
1183         VM_WARN_ON(addr >= end);
1184
1185         /*
1186          * Can it merge with the predecessor?
1187          */
1188         if (prev && prev->vm_end == addr &&
1189                         mpol_equal(vma_policy(prev), policy) &&
1190                         can_vma_merge_after(prev, vm_flags,
1191                                             anon_vma, file, pgoff,
1192                                             vm_userfaultfd_ctx)) {
1193                 /*
1194                  * OK, it can.  Can we now merge in the successor as well?
1195                  */
1196                 if (next && end == next->vm_start &&
1197                                 mpol_equal(policy, vma_policy(next)) &&
1198                                 can_vma_merge_before(next, vm_flags,
1199                                                      anon_vma, file,
1200                                                      pgoff+pglen,
1201                                                      vm_userfaultfd_ctx) &&
1202                                 is_mergeable_anon_vma(prev->anon_vma,
1203                                                       next->anon_vma, NULL)) {
1204                                                         /* cases 1, 6 */
1205                         err = __vma_adjust(prev, prev->vm_start,
1206                                          next->vm_end, prev->vm_pgoff, NULL,
1207                                          prev);
1208                 } else                                  /* cases 2, 5, 7 */
1209                         err = __vma_adjust(prev, prev->vm_start,
1210                                          end, prev->vm_pgoff, NULL, prev);
1211                 if (err)
1212                         return NULL;
1213                 khugepaged_enter_vma_merge(prev, vm_flags);
1214                 return prev;
1215         }
1216
1217         /*
1218          * Can this new request be merged in front of next?
1219          */
1220         if (next && end == next->vm_start &&
1221                         mpol_equal(policy, vma_policy(next)) &&
1222                         can_vma_merge_before(next, vm_flags,
1223                                              anon_vma, file, pgoff+pglen,
1224                                              vm_userfaultfd_ctx)) {
1225                 if (prev && addr < prev->vm_end)        /* case 4 */
1226                         err = __vma_adjust(prev, prev->vm_start,
1227                                          addr, prev->vm_pgoff, NULL, next);
1228                 else {                                  /* cases 3, 8 */
1229                         err = __vma_adjust(area, addr, next->vm_end,
1230                                          next->vm_pgoff - pglen, NULL, next);
1231                         /*
1232                          * In case 3 area is already equal to next and
1233                          * this is a noop, but in case 8 "area" has
1234                          * been removed and next was expanded over it.
1235                          */
1236                         area = next;
1237                 }
1238                 if (err)
1239                         return NULL;
1240                 khugepaged_enter_vma_merge(area, vm_flags);
1241                 return area;
1242         }
1243
1244         return NULL;
1245 }
1246
1247 /*
1248  * Rough compatibility check to quickly see if it's even worth looking
1249  * at sharing an anon_vma.
1250  *
1251  * They need to have the same vm_file, and the flags can only differ
1252  * in things that mprotect may change.
1253  *
1254  * NOTE! The fact that we share an anon_vma doesn't _have_ to mean that
1255  * we can merge the two vma's. For example, we refuse to merge a vma if
1256  * there is a vm_ops->close() function, because that indicates that the
1257  * driver is doing some kind of reference counting. But that doesn't
1258  * really matter for the anon_vma sharing case.
1259  */
1260 static int anon_vma_compatible(struct vm_area_struct *a, struct vm_area_struct *b)
1261 {
1262         return a->vm_end == b->vm_start &&
1263                 mpol_equal(vma_policy(a), vma_policy(b)) &&
1264                 a->vm_file == b->vm_file &&
1265                 !((a->vm_flags ^ b->vm_flags) & ~(VM_ACCESS_FLAGS | VM_SOFTDIRTY)) &&
1266                 b->vm_pgoff == a->vm_pgoff + ((b->vm_start - a->vm_start) >> PAGE_SHIFT);
1267 }
1268
1269 /*
1270  * Do some basic sanity checking to see if we can re-use the anon_vma
1271  * from 'old'. The 'a'/'b' vma's are in VM order - one of them will be
1272  * the same as 'old', the other will be the new one that is trying
1273  * to share the anon_vma.
1274  *
1275  * NOTE! This runs with mm_sem held for reading, so it is possible that
1276  * the anon_vma of 'old' is concurrently in the process of being set up
1277  * by another page fault trying to merge _that_. But that's ok: if it
1278  * is being set up, that automatically means that it will be a singleton
1279  * acceptable for merging, so we can do all of this optimistically. But
1280  * we do that READ_ONCE() to make sure that we never re-load the pointer.
1281  *
1282  * IOW: that the "list_is_singular()" test on the anon_vma_chain only
1283  * matters for the 'stable anon_vma' case (ie the thing we want to avoid
1284  * is to return an anon_vma that is "complex" due to having gone through
1285  * a fork).
1286  *
1287  * We also make sure that the two vma's are compatible (adjacent,
1288  * and with the same memory policies). That's all stable, even with just
1289  * a read lock on the mm_sem.
1290  */
1291 static struct anon_vma *reusable_anon_vma(struct vm_area_struct *old, struct vm_area_struct *a, struct vm_area_struct *b)
1292 {
1293         if (anon_vma_compatible(a, b)) {
1294                 struct anon_vma *anon_vma = READ_ONCE(old->anon_vma);
1295
1296                 if (anon_vma && list_is_singular(&old->anon_vma_chain))
1297                         return anon_vma;
1298         }
1299         return NULL;
1300 }
1301
1302 /*
1303  * find_mergeable_anon_vma is used by anon_vma_prepare, to check
1304  * neighbouring vmas for a suitable anon_vma, before it goes off
1305  * to allocate a new anon_vma.  It checks because a repetitive
1306  * sequence of mprotects and faults may otherwise lead to distinct
1307  * anon_vmas being allocated, preventing vma merge in subsequent
1308  * mprotect.
1309  */
1310 struct anon_vma *find_mergeable_anon_vma(struct vm_area_struct *vma)
1311 {
1312         struct anon_vma *anon_vma = NULL;
1313
1314         /* Try next first. */
1315         if (vma->vm_next) {
1316                 anon_vma = reusable_anon_vma(vma->vm_next, vma, vma->vm_next);
1317                 if (anon_vma)
1318                         return anon_vma;
1319         }
1320
1321         /* Try prev next. */
1322         if (vma->vm_prev)
1323                 anon_vma = reusable_anon_vma(vma->vm_prev, vma->vm_prev, vma);
1324
1325         /*
1326          * We might reach here with anon_vma == NULL if we can't find
1327          * any reusable anon_vma.
1328          * There's no absolute need to look only at touching neighbours:
1329          * we could search further afield for "compatible" anon_vmas.
1330          * But it would probably just be a waste of time searching,
1331          * or lead to too many vmas hanging off the same anon_vma.
1332          * We're trying to allow mprotect remerging later on,
1333          * not trying to minimize memory used for anon_vmas.
1334          */
1335         return anon_vma;
1336 }
1337
1338 /*
1339  * If a hint addr is less than mmap_min_addr change hint to be as
1340  * low as possible but still greater than mmap_min_addr
1341  */
1342 static inline unsigned long round_hint_to_min(unsigned long hint)
1343 {
1344         hint &= PAGE_MASK;
1345         if (((void *)hint != NULL) &&
1346             (hint < mmap_min_addr))
1347                 return PAGE_ALIGN(mmap_min_addr);
1348         return hint;
1349 }
1350
1351 static inline int mlock_future_check(struct mm_struct *mm,
1352                                      unsigned long flags,
1353                                      unsigned long len)
1354 {
1355         unsigned long locked, lock_limit;
1356
1357         /*  mlock MCL_FUTURE? */
1358         if (flags & VM_LOCKED) {
1359                 locked = len >> PAGE_SHIFT;
1360                 locked += mm->locked_vm;
1361                 lock_limit = rlimit(RLIMIT_MEMLOCK);
1362                 lock_limit >>= PAGE_SHIFT;
1363                 if (locked > lock_limit && !capable(CAP_IPC_LOCK))
1364                         return -EAGAIN;
1365         }
1366         return 0;
1367 }
1368
1369 static inline u64 file_mmap_size_max(struct file *file, struct inode *inode)
1370 {
1371         if (S_ISREG(inode->i_mode))
1372                 return MAX_LFS_FILESIZE;
1373
1374         if (S_ISBLK(inode->i_mode))
1375                 return MAX_LFS_FILESIZE;
1376
1377         if (S_ISSOCK(inode->i_mode))
1378                 return MAX_LFS_FILESIZE;
1379
1380         /* Special "we do even unsigned file positions" case */
1381         if (file->f_mode & FMODE_UNSIGNED_OFFSET)
1382                 return 0;
1383
1384         /* Yes, random drivers might want more. But I'm tired of buggy drivers */
1385         return ULONG_MAX;
1386 }
1387
1388 static inline bool file_mmap_ok(struct file *file, struct inode *inode,
1389                                 unsigned long pgoff, unsigned long len)
1390 {
1391         u64 maxsize = file_mmap_size_max(file, inode);
1392
1393         if (maxsize && len > maxsize)
1394                 return false;
1395         maxsize -= len;
1396         if (pgoff > maxsize >> PAGE_SHIFT)
1397                 return false;
1398         return true;
1399 }
1400
1401 /*
1402  * The caller must write-lock current->mm->mmap_lock.
1403  */
1404 unsigned long do_mmap(struct file *file, unsigned long addr,
1405                         unsigned long len, unsigned long prot,
1406                         unsigned long flags, unsigned long pgoff,
1407                         unsigned long *populate, struct list_head *uf)
1408 {
1409         struct mm_struct *mm = current->mm;
1410         vm_flags_t vm_flags;
1411         int pkey = 0;
1412
1413         *populate = 0;
1414
1415         if (!len)
1416                 return -EINVAL;
1417
1418         /*
1419          * Does the application expect PROT_READ to imply PROT_EXEC?
1420          *
1421          * (the exception is when the underlying filesystem is noexec
1422          *  mounted, in which case we dont add PROT_EXEC.)
1423          */
1424         if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC))
1425                 if (!(file && path_noexec(&file->f_path)))
1426                         prot |= PROT_EXEC;
1427
1428         /* force arch specific MAP_FIXED handling in get_unmapped_area */
1429         if (flags & MAP_FIXED_NOREPLACE)
1430                 flags |= MAP_FIXED;
1431
1432         if (!(flags & MAP_FIXED))
1433                 addr = round_hint_to_min(addr);
1434
1435         /* Careful about overflows.. */
1436         len = PAGE_ALIGN(len);
1437         if (!len)
1438                 return -ENOMEM;
1439
1440         /* offset overflow? */
1441         if ((pgoff + (len >> PAGE_SHIFT)) < pgoff)
1442                 return -EOVERFLOW;
1443
1444         /* Too many mappings? */
1445         if (mm->map_count > sysctl_max_map_count)
1446                 return -ENOMEM;
1447
1448         /* Obtain the address to map to. we verify (or select) it and ensure
1449          * that it represents a valid section of the address space.
1450          */
1451         addr = get_unmapped_area(file, addr, len, pgoff, flags);
1452         if (IS_ERR_VALUE(addr))
1453                 return addr;
1454
1455         if (flags & MAP_FIXED_NOREPLACE) {
1456                 struct vm_area_struct *vma = find_vma(mm, addr);
1457
1458                 if (vma && vma->vm_start < addr + len)
1459                         return -EEXIST;
1460         }
1461
1462         if (prot == PROT_EXEC) {
1463                 pkey = execute_only_pkey(mm);
1464                 if (pkey < 0)
1465                         pkey = 0;
1466         }
1467
1468         /* Do simple checking here so the lower-level routines won't have
1469          * to. we assume access permissions have been handled by the open
1470          * of the memory object, so we don't do any here.
1471          */
1472         vm_flags = calc_vm_prot_bits(prot, pkey) | calc_vm_flag_bits(flags) |
1473                         mm->def_flags | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
1474
1475         if (flags & MAP_LOCKED)
1476                 if (!can_do_mlock())
1477                         return -EPERM;
1478
1479         if (mlock_future_check(mm, vm_flags, len))
1480                 return -EAGAIN;
1481
1482         if (file) {
1483                 struct inode *inode = file_inode(file);
1484                 unsigned long flags_mask;
1485
1486                 if (!file_mmap_ok(file, inode, pgoff, len))
1487                         return -EOVERFLOW;
1488
1489                 flags_mask = LEGACY_MAP_MASK | file->f_op->mmap_supported_flags;
1490
1491                 switch (flags & MAP_TYPE) {
1492                 case MAP_SHARED:
1493                         /*
1494                          * Force use of MAP_SHARED_VALIDATE with non-legacy
1495                          * flags. E.g. MAP_SYNC is dangerous to use with
1496                          * MAP_SHARED as you don't know which consistency model
1497                          * you will get. We silently ignore unsupported flags
1498                          * with MAP_SHARED to preserve backward compatibility.
1499                          */
1500                         flags &= LEGACY_MAP_MASK;
1501                         fallthrough;
1502                 case MAP_SHARED_VALIDATE:
1503                         if (flags & ~flags_mask)
1504                                 return -EOPNOTSUPP;
1505                         if (prot & PROT_WRITE) {
1506                                 if (!(file->f_mode & FMODE_WRITE))
1507                                         return -EACCES;
1508                                 if (IS_SWAPFILE(file->f_mapping->host))
1509                                         return -ETXTBSY;
1510                         }
1511
1512                         /*
1513                          * Make sure we don't allow writing to an append-only
1514                          * file..
1515                          */
1516                         if (IS_APPEND(inode) && (file->f_mode & FMODE_WRITE))
1517                                 return -EACCES;
1518
1519                         /*
1520                          * Make sure there are no mandatory locks on the file.
1521                          */
1522                         if (locks_verify_locked(file))
1523                                 return -EAGAIN;
1524
1525                         vm_flags |= VM_SHARED | VM_MAYSHARE;
1526                         if (!(file->f_mode & FMODE_WRITE))
1527                                 vm_flags &= ~(VM_MAYWRITE | VM_SHARED);
1528                         fallthrough;
1529                 case MAP_PRIVATE:
1530                         if (!(file->f_mode & FMODE_READ))
1531                                 return -EACCES;
1532                         if (path_noexec(&file->f_path)) {
1533                                 if (vm_flags & VM_EXEC)
1534                                         return -EPERM;
1535                                 vm_flags &= ~VM_MAYEXEC;
1536                         }
1537
1538                         if (!file->f_op->mmap)
1539                                 return -ENODEV;
1540                         if (vm_flags & (VM_GROWSDOWN|VM_GROWSUP))
1541                                 return -EINVAL;
1542                         break;
1543
1544                 default:
1545                         return -EINVAL;
1546                 }
1547         } else {
1548                 switch (flags & MAP_TYPE) {
1549                 case MAP_SHARED:
1550                         if (vm_flags & (VM_GROWSDOWN|VM_GROWSUP))
1551                                 return -EINVAL;
1552                         /*
1553                          * Ignore pgoff.
1554                          */
1555                         pgoff = 0;
1556                         vm_flags |= VM_SHARED | VM_MAYSHARE;
1557                         break;
1558                 case MAP_PRIVATE:
1559                         /*
1560                          * Set pgoff according to addr for anon_vma.
1561                          */
1562                         pgoff = addr >> PAGE_SHIFT;
1563                         break;
1564                 default:
1565                         return -EINVAL;
1566                 }
1567         }
1568
1569         /*
1570          * Set 'VM_NORESERVE' if we should not account for the
1571          * memory use of this mapping.
1572          */
1573         if (flags & MAP_NORESERVE) {
1574                 /* We honor MAP_NORESERVE if allowed to overcommit */
1575                 if (sysctl_overcommit_memory != OVERCOMMIT_NEVER)
1576                         vm_flags |= VM_NORESERVE;
1577
1578                 /* hugetlb applies strict overcommit unless MAP_NORESERVE */
1579                 if (file && is_file_hugepages(file))
1580                         vm_flags |= VM_NORESERVE;
1581         }
1582
1583         addr = mmap_region(file, addr, len, vm_flags, pgoff, uf);
1584         if (!IS_ERR_VALUE(addr) &&
1585             ((vm_flags & VM_LOCKED) ||
1586              (flags & (MAP_POPULATE | MAP_NONBLOCK)) == MAP_POPULATE))
1587                 *populate = len;
1588         return addr;
1589 }
1590
1591 unsigned long ksys_mmap_pgoff(unsigned long addr, unsigned long len,
1592                               unsigned long prot, unsigned long flags,
1593                               unsigned long fd, unsigned long pgoff)
1594 {
1595         struct file *file = NULL;
1596         unsigned long retval;
1597
1598         if (!(flags & MAP_ANONYMOUS)) {
1599                 audit_mmap_fd(fd, flags);
1600                 file = fget(fd);
1601                 if (!file)
1602                         return -EBADF;
1603                 if (is_file_hugepages(file)) {
1604                         len = ALIGN(len, huge_page_size(hstate_file(file)));
1605                 } else if (unlikely(flags & MAP_HUGETLB)) {
1606                         retval = -EINVAL;
1607                         goto out_fput;
1608                 }
1609         } else if (flags & MAP_HUGETLB) {
1610                 struct user_struct *user = NULL;
1611                 struct hstate *hs;
1612
1613                 hs = hstate_sizelog((flags >> MAP_HUGE_SHIFT) & MAP_HUGE_MASK);
1614                 if (!hs)
1615                         return -EINVAL;
1616
1617                 len = ALIGN(len, huge_page_size(hs));
1618                 /*
1619                  * VM_NORESERVE is used because the reservations will be
1620                  * taken when vm_ops->mmap() is called
1621                  * A dummy user value is used because we are not locking
1622                  * memory so no accounting is necessary
1623                  */
1624                 file = hugetlb_file_setup(HUGETLB_ANON_FILE, len,
1625                                 VM_NORESERVE,
1626                                 &user, HUGETLB_ANONHUGE_INODE,
1627                                 (flags >> MAP_HUGE_SHIFT) & MAP_HUGE_MASK);
1628                 if (IS_ERR(file))
1629                         return PTR_ERR(file);
1630         }
1631
1632         flags &= ~(MAP_EXECUTABLE | MAP_DENYWRITE);
1633
1634         retval = vm_mmap_pgoff(file, addr, len, prot, flags, pgoff);
1635 out_fput:
1636         if (file)
1637                 fput(file);
1638         return retval;
1639 }
1640
1641 SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len,
1642                 unsigned long, prot, unsigned long, flags,
1643                 unsigned long, fd, unsigned long, pgoff)
1644 {
1645         return ksys_mmap_pgoff(addr, len, prot, flags, fd, pgoff);
1646 }
1647
1648 #ifdef __ARCH_WANT_SYS_OLD_MMAP
1649 struct mmap_arg_struct {
1650         unsigned long addr;
1651         unsigned long len;
1652         unsigned long prot;
1653         unsigned long flags;
1654         unsigned long fd;
1655         unsigned long offset;
1656 };
1657
1658 SYSCALL_DEFINE1(old_mmap, struct mmap_arg_struct __user *, arg)
1659 {
1660         struct mmap_arg_struct a;
1661
1662         if (copy_from_user(&a, arg, sizeof(a)))
1663                 return -EFAULT;
1664         if (offset_in_page(a.offset))
1665                 return -EINVAL;
1666
1667         return ksys_mmap_pgoff(a.addr, a.len, a.prot, a.flags, a.fd,
1668                                a.offset >> PAGE_SHIFT);
1669 }
1670 #endif /* __ARCH_WANT_SYS_OLD_MMAP */
1671
1672 /*
1673  * Some shared mappings will want the pages marked read-only
1674  * to track write events. If so, we'll downgrade vm_page_prot
1675  * to the private version (using protection_map[] without the
1676  * VM_SHARED bit).
1677  */
1678 int vma_wants_writenotify(struct vm_area_struct *vma, pgprot_t vm_page_prot)
1679 {
1680         vm_flags_t vm_flags = vma->vm_flags;
1681         const struct vm_operations_struct *vm_ops = vma->vm_ops;
1682
1683         /* If it was private or non-writable, the write bit is already clear */
1684         if ((vm_flags & (VM_WRITE|VM_SHARED)) != ((VM_WRITE|VM_SHARED)))
1685                 return 0;
1686
1687         /* The backer wishes to know when pages are first written to? */
1688         if (vm_ops && (vm_ops->page_mkwrite || vm_ops->pfn_mkwrite))
1689                 return 1;
1690
1691         /* The open routine did something to the protections that pgprot_modify
1692          * won't preserve? */
1693         if (pgprot_val(vm_page_prot) !=
1694             pgprot_val(vm_pgprot_modify(vm_page_prot, vm_flags)))
1695                 return 0;
1696
1697         /* Do we need to track softdirty? */
1698         if (IS_ENABLED(CONFIG_MEM_SOFT_DIRTY) && !(vm_flags & VM_SOFTDIRTY))
1699                 return 1;
1700
1701         /* Specialty mapping? */
1702         if (vm_flags & VM_PFNMAP)
1703                 return 0;
1704
1705         /* Can the mapping track the dirty pages? */
1706         return vma->vm_file && vma->vm_file->f_mapping &&
1707                 mapping_can_writeback(vma->vm_file->f_mapping);
1708 }
1709
1710 /*
1711  * We account for memory if it's a private writeable mapping,
1712  * not hugepages and VM_NORESERVE wasn't set.
1713  */
1714 static inline int accountable_mapping(struct file *file, vm_flags_t vm_flags)
1715 {
1716         /*
1717          * hugetlb has its own accounting separate from the core VM
1718          * VM_HUGETLB may not be set yet so we cannot check for that flag.
1719          */
1720         if (file && is_file_hugepages(file))
1721                 return 0;
1722
1723         return (vm_flags & (VM_NORESERVE | VM_SHARED | VM_WRITE)) == VM_WRITE;
1724 }
1725
1726 unsigned long mmap_region(struct file *file, unsigned long addr,
1727                 unsigned long len, vm_flags_t vm_flags, unsigned long pgoff,
1728                 struct list_head *uf)
1729 {
1730         struct mm_struct *mm = current->mm;
1731         struct vm_area_struct *vma, *prev, *merge;
1732         int error;
1733         struct rb_node **rb_link, *rb_parent;
1734         unsigned long charged = 0;
1735
1736         /* Check against address space limit. */
1737         if (!may_expand_vm(mm, vm_flags, len >> PAGE_SHIFT)) {
1738                 unsigned long nr_pages;
1739
1740                 /*
1741                  * MAP_FIXED may remove pages of mappings that intersects with
1742                  * requested mapping. Account for the pages it would unmap.
1743                  */
1744                 nr_pages = count_vma_pages_range(mm, addr, addr + len);
1745
1746                 if (!may_expand_vm(mm, vm_flags,
1747                                         (len >> PAGE_SHIFT) - nr_pages))
1748                         return -ENOMEM;
1749         }
1750
1751         /* Clear old maps, set up prev, rb_link, rb_parent, and uf */
1752         if (munmap_vma_range(mm, addr, len, &prev, &rb_link, &rb_parent, uf))
1753                 return -ENOMEM;
1754         /*
1755          * Private writable mapping: check memory availability
1756          */
1757         if (accountable_mapping(file, vm_flags)) {
1758                 charged = len >> PAGE_SHIFT;
1759                 if (security_vm_enough_memory_mm(mm, charged))
1760                         return -ENOMEM;
1761                 vm_flags |= VM_ACCOUNT;
1762         }
1763
1764         /*
1765          * Can we just expand an old mapping?
1766          */
1767         vma = vma_merge(mm, prev, addr, addr + len, vm_flags,
1768                         NULL, file, pgoff, NULL, NULL_VM_UFFD_CTX);
1769         if (vma)
1770                 goto out;
1771
1772         /*
1773          * Determine the object being mapped and call the appropriate
1774          * specific mapper. the address has already been validated, but
1775          * not unmapped, but the maps are removed from the list.
1776          */
1777         vma = vm_area_alloc(mm);
1778         if (!vma) {
1779                 error = -ENOMEM;
1780                 goto unacct_error;
1781         }
1782
1783         vma->vm_start = addr;
1784         vma->vm_end = addr + len;
1785         vma->vm_flags = vm_flags;
1786         vma->vm_page_prot = vm_get_page_prot(vm_flags);
1787         vma->vm_pgoff = pgoff;
1788
1789         if (file) {
1790                 if (vm_flags & VM_DENYWRITE) {
1791                         error = deny_write_access(file);
1792                         if (error)
1793                                 goto free_vma;
1794                 }
1795                 if (vm_flags & VM_SHARED) {
1796                         error = mapping_map_writable(file->f_mapping);
1797                         if (error)
1798                                 goto allow_write_and_free_vma;
1799                 }
1800
1801                 /* ->mmap() can change vma->vm_file, but must guarantee that
1802                  * vma_link() below can deny write-access if VM_DENYWRITE is set
1803                  * and map writably if VM_SHARED is set. This usually means the
1804                  * new file must not have been exposed to user-space, yet.
1805                  */
1806                 vma->vm_file = get_file(file);
1807                 error = call_mmap(file, vma);
1808                 if (error)
1809                         goto unmap_and_free_vma;
1810
1811                 /* Can addr have changed??
1812                  *
1813                  * Answer: Yes, several device drivers can do it in their
1814                  *         f_op->mmap method. -DaveM
1815                  * Bug: If addr is changed, prev, rb_link, rb_parent should
1816                  *      be updated for vma_link()
1817                  */
1818                 WARN_ON_ONCE(addr != vma->vm_start);
1819
1820                 addr = vma->vm_start;
1821
1822                 /* If vm_flags changed after call_mmap(), we should try merge vma again
1823                  * as we may succeed this time.
1824                  */
1825                 if (unlikely(vm_flags != vma->vm_flags && prev)) {
1826                         merge = vma_merge(mm, prev, vma->vm_start, vma->vm_end, vma->vm_flags,
1827                                 NULL, vma->vm_file, vma->vm_pgoff, NULL, NULL_VM_UFFD_CTX);
1828                         if (merge) {
1829                                 /* ->mmap() can change vma->vm_file and fput the original file. So
1830                                  * fput the vma->vm_file here or we would add an extra fput for file
1831                                  * and cause general protection fault ultimately.
1832                                  */
1833                                 fput(vma->vm_file);
1834                                 vm_area_free(vma);
1835                                 vma = merge;
1836                                 /* Update vm_flags to pick up the change. */
1837                                 vm_flags = vma->vm_flags;
1838                                 goto unmap_writable;
1839                         }
1840                 }
1841
1842                 vm_flags = vma->vm_flags;
1843         } else if (vm_flags & VM_SHARED) {
1844                 error = shmem_zero_setup(vma);
1845                 if (error)
1846                         goto free_vma;
1847         } else {
1848                 vma_set_anonymous(vma);
1849         }
1850
1851         /* Allow architectures to sanity-check the vm_flags */
1852         if (!arch_validate_flags(vma->vm_flags)) {
1853                 error = -EINVAL;
1854                 if (file)
1855                         goto unmap_and_free_vma;
1856                 else
1857                         goto free_vma;
1858         }
1859
1860         vma_link(mm, vma, prev, rb_link, rb_parent);
1861         /* Once vma denies write, undo our temporary denial count */
1862         if (file) {
1863 unmap_writable:
1864                 if (vm_flags & VM_SHARED)
1865                         mapping_unmap_writable(file->f_mapping);
1866                 if (vm_flags & VM_DENYWRITE)
1867                         allow_write_access(file);
1868         }
1869         file = vma->vm_file;
1870 out:
1871         perf_event_mmap(vma);
1872
1873         vm_stat_account(mm, vm_flags, len >> PAGE_SHIFT);
1874         if (vm_flags & VM_LOCKED) {
1875                 if ((vm_flags & VM_SPECIAL) || vma_is_dax(vma) ||
1876                                         is_vm_hugetlb_page(vma) ||
1877                                         vma == get_gate_vma(current->mm))
1878                         vma->vm_flags &= VM_LOCKED_CLEAR_MASK;
1879                 else
1880                         mm->locked_vm += (len >> PAGE_SHIFT);
1881         }
1882
1883         if (file)
1884                 uprobe_mmap(vma);
1885
1886         /*
1887          * New (or expanded) vma always get soft dirty status.
1888          * Otherwise user-space soft-dirty page tracker won't
1889          * be able to distinguish situation when vma area unmapped,
1890          * then new mapped in-place (which must be aimed as
1891          * a completely new data area).
1892          */
1893         vma->vm_flags |= VM_SOFTDIRTY;
1894
1895         vma_set_page_prot(vma);
1896
1897         return addr;
1898
1899 unmap_and_free_vma:
1900         vma->vm_file = NULL;
1901         fput(file);
1902
1903         /* Undo any partial mapping done by a device driver. */
1904         unmap_region(mm, vma, prev, vma->vm_start, vma->vm_end);
1905         charged = 0;
1906         if (vm_flags & VM_SHARED)
1907                 mapping_unmap_writable(file->f_mapping);
1908 allow_write_and_free_vma:
1909         if (vm_flags & VM_DENYWRITE)
1910                 allow_write_access(file);
1911 free_vma:
1912         vm_area_free(vma);
1913 unacct_error:
1914         if (charged)
1915                 vm_unacct_memory(charged);
1916         return error;
1917 }
1918
1919 static unsigned long unmapped_area(struct vm_unmapped_area_info *info)
1920 {
1921         /*
1922          * We implement the search by looking for an rbtree node that
1923          * immediately follows a suitable gap. That is,
1924          * - gap_start = vma->vm_prev->vm_end <= info->high_limit - length;
1925          * - gap_end   = vma->vm_start        >= info->low_limit  + length;
1926          * - gap_end - gap_start >= length
1927          */
1928
1929         struct mm_struct *mm = current->mm;
1930         struct vm_area_struct *vma;
1931         unsigned long length, low_limit, high_limit, gap_start, gap_end;
1932
1933         /* Adjust search length to account for worst case alignment overhead */
1934         length = info->length + info->align_mask;
1935         if (length < info->length)
1936                 return -ENOMEM;
1937
1938         /* Adjust search limits by the desired length */
1939         if (info->high_limit < length)
1940                 return -ENOMEM;
1941         high_limit = info->high_limit - length;
1942
1943         if (info->low_limit > high_limit)
1944                 return -ENOMEM;
1945         low_limit = info->low_limit + length;
1946
1947         /* Check if rbtree root looks promising */
1948         if (RB_EMPTY_ROOT(&mm->mm_rb))
1949                 goto check_highest;
1950         vma = rb_entry(mm->mm_rb.rb_node, struct vm_area_struct, vm_rb);
1951         if (vma->rb_subtree_gap < length)
1952                 goto check_highest;
1953
1954         while (true) {
1955                 /* Visit left subtree if it looks promising */
1956                 gap_end = vm_start_gap(vma);
1957                 if (gap_end >= low_limit && vma->vm_rb.rb_left) {
1958                         struct vm_area_struct *left =
1959                                 rb_entry(vma->vm_rb.rb_left,
1960                                          struct vm_area_struct, vm_rb);
1961                         if (left->rb_subtree_gap >= length) {
1962                                 vma = left;
1963                                 continue;
1964                         }
1965                 }
1966
1967                 gap_start = vma->vm_prev ? vm_end_gap(vma->vm_prev) : 0;
1968 check_current:
1969                 /* Check if current node has a suitable gap */
1970                 if (gap_start > high_limit)
1971                         return -ENOMEM;
1972                 if (gap_end >= low_limit &&
1973                     gap_end > gap_start && gap_end - gap_start >= length)
1974                         goto found;
1975
1976                 /* Visit right subtree if it looks promising */
1977                 if (vma->vm_rb.rb_right) {
1978                         struct vm_area_struct *right =
1979                                 rb_entry(vma->vm_rb.rb_right,
1980                                          struct vm_area_struct, vm_rb);
1981                         if (right->rb_subtree_gap >= length) {
1982                                 vma = right;
1983                                 continue;
1984                         }
1985                 }
1986
1987                 /* Go back up the rbtree to find next candidate node */
1988                 while (true) {
1989                         struct rb_node *prev = &vma->vm_rb;
1990                         if (!rb_parent(prev))
1991                                 goto check_highest;
1992                         vma = rb_entry(rb_parent(prev),
1993                                        struct vm_area_struct, vm_rb);
1994                         if (prev == vma->vm_rb.rb_left) {
1995                                 gap_start = vm_end_gap(vma->vm_prev);
1996                                 gap_end = vm_start_gap(vma);
1997                                 goto check_current;
1998                         }
1999                 }
2000         }
2001
2002 check_highest:
2003         /* Check highest gap, which does not precede any rbtree node */
2004         gap_start = mm->highest_vm_end;
2005         gap_end = ULONG_MAX;  /* Only for VM_BUG_ON below */
2006         if (gap_start > high_limit)
2007                 return -ENOMEM;
2008
2009 found:
2010         /* We found a suitable gap. Clip it with the original low_limit. */
2011         if (gap_start < info->low_limit)
2012                 gap_start = info->low_limit;
2013
2014         /* Adjust gap address to the desired alignment */
2015         gap_start += (info->align_offset - gap_start) & info->align_mask;
2016
2017         VM_BUG_ON(gap_start + info->length > info->high_limit);
2018         VM_BUG_ON(gap_start + info->length > gap_end);
2019         return gap_start;
2020 }
2021
2022 static unsigned long unmapped_area_topdown(struct vm_unmapped_area_info *info)
2023 {
2024         struct mm_struct *mm = current->mm;
2025         struct vm_area_struct *vma;
2026         unsigned long length, low_limit, high_limit, gap_start, gap_end;
2027
2028         /* Adjust search length to account for worst case alignment overhead */
2029         length = info->length + info->align_mask;
2030         if (length < info->length)
2031                 return -ENOMEM;
2032
2033         /*
2034          * Adjust search limits by the desired length.
2035          * See implementation comment at top of unmapped_area().
2036          */
2037         gap_end = info->high_limit;
2038         if (gap_end < length)
2039                 return -ENOMEM;
2040         high_limit = gap_end - length;
2041
2042         if (info->low_limit > high_limit)
2043                 return -ENOMEM;
2044         low_limit = info->low_limit + length;
2045
2046         /* Check highest gap, which does not precede any rbtree node */
2047         gap_start = mm->highest_vm_end;
2048         if (gap_start <= high_limit)
2049                 goto found_highest;
2050
2051         /* Check if rbtree root looks promising */
2052         if (RB_EMPTY_ROOT(&mm->mm_rb))
2053                 return -ENOMEM;
2054         vma = rb_entry(mm->mm_rb.rb_node, struct vm_area_struct, vm_rb);
2055         if (vma->rb_subtree_gap < length)
2056                 return -ENOMEM;
2057
2058         while (true) {
2059                 /* Visit right subtree if it looks promising */
2060                 gap_start = vma->vm_prev ? vm_end_gap(vma->vm_prev) : 0;
2061                 if (gap_start <= high_limit && vma->vm_rb.rb_right) {
2062                         struct vm_area_struct *right =
2063                                 rb_entry(vma->vm_rb.rb_right,
2064                                          struct vm_area_struct, vm_rb);
2065                         if (right->rb_subtree_gap >= length) {
2066                                 vma = right;
2067                                 continue;
2068                         }
2069                 }
2070
2071 check_current:
2072                 /* Check if current node has a suitable gap */
2073                 gap_end = vm_start_gap(vma);
2074                 if (gap_end < low_limit)
2075                         return -ENOMEM;
2076                 if (gap_start <= high_limit &&
2077                     gap_end > gap_start && gap_end - gap_start >= length)
2078                         goto found;
2079
2080                 /* Visit left subtree if it looks promising */
2081                 if (vma->vm_rb.rb_left) {
2082                         struct vm_area_struct *left =
2083                                 rb_entry(vma->vm_rb.rb_left,
2084                                          struct vm_area_struct, vm_rb);
2085                         if (left->rb_subtree_gap >= length) {
2086                                 vma = left;
2087                                 continue;
2088                         }
2089                 }
2090
2091                 /* Go back up the rbtree to find next candidate node */
2092                 while (true) {
2093                         struct rb_node *prev = &vma->vm_rb;
2094                         if (!rb_parent(prev))
2095                                 return -ENOMEM;
2096                         vma = rb_entry(rb_parent(prev),
2097                                        struct vm_area_struct, vm_rb);
2098                         if (prev == vma->vm_rb.rb_right) {
2099                                 gap_start = vma->vm_prev ?
2100                                         vm_end_gap(vma->vm_prev) : 0;
2101                                 goto check_current;
2102                         }
2103                 }
2104         }
2105
2106 found:
2107         /* We found a suitable gap. Clip it with the original high_limit. */
2108         if (gap_end > info->high_limit)
2109                 gap_end = info->high_limit;
2110
2111 found_highest:
2112         /* Compute highest gap address at the desired alignment */
2113         gap_end -= info->length;
2114         gap_end -= (gap_end - info->align_offset) & info->align_mask;
2115
2116         VM_BUG_ON(gap_end < info->low_limit);
2117         VM_BUG_ON(gap_end < gap_start);
2118         return gap_end;
2119 }
2120
2121 /*
2122  * Search for an unmapped address range.
2123  *
2124  * We are looking for a range that:
2125  * - does not intersect with any VMA;
2126  * - is contained within the [low_limit, high_limit) interval;
2127  * - is at least the desired size.
2128  * - satisfies (begin_addr & align_mask) == (align_offset & align_mask)
2129  */
2130 unsigned long vm_unmapped_area(struct vm_unmapped_area_info *info)
2131 {
2132         unsigned long addr;
2133
2134         if (info->flags & VM_UNMAPPED_AREA_TOPDOWN)
2135                 addr = unmapped_area_topdown(info);
2136         else
2137                 addr = unmapped_area(info);
2138
2139         trace_vm_unmapped_area(addr, info);
2140         return addr;
2141 }
2142
2143 #ifndef arch_get_mmap_end
2144 #define arch_get_mmap_end(addr) (TASK_SIZE)
2145 #endif
2146
2147 #ifndef arch_get_mmap_base
2148 #define arch_get_mmap_base(addr, base) (base)
2149 #endif
2150
2151 /* Get an address range which is currently unmapped.
2152  * For shmat() with addr=0.
2153  *
2154  * Ugly calling convention alert:
2155  * Return value with the low bits set means error value,
2156  * ie
2157  *      if (ret & ~PAGE_MASK)
2158  *              error = ret;
2159  *
2160  * This function "knows" that -ENOMEM has the bits set.
2161  */
2162 #ifndef HAVE_ARCH_UNMAPPED_AREA
2163 unsigned long
2164 arch_get_unmapped_area(struct file *filp, unsigned long addr,
2165                 unsigned long len, unsigned long pgoff, unsigned long flags)
2166 {
2167         struct mm_struct *mm = current->mm;
2168         struct vm_area_struct *vma, *prev;
2169         struct vm_unmapped_area_info info;
2170         const unsigned long mmap_end = arch_get_mmap_end(addr);
2171
2172         if (len > mmap_end - mmap_min_addr)
2173                 return -ENOMEM;
2174
2175         if (flags & MAP_FIXED)
2176                 return addr;
2177
2178         if (addr) {
2179                 addr = PAGE_ALIGN(addr);
2180                 vma = find_vma_prev(mm, addr, &prev);
2181                 if (mmap_end - len >= addr && addr >= mmap_min_addr &&
2182                     (!vma || addr + len <= vm_start_gap(vma)) &&
2183                     (!prev || addr >= vm_end_gap(prev)))
2184                         return addr;
2185         }
2186
2187         info.flags = 0;
2188         info.length = len;
2189         info.low_limit = mm->mmap_base;
2190         info.high_limit = mmap_end;
2191         info.align_mask = 0;
2192         info.align_offset = 0;
2193         return vm_unmapped_area(&info);
2194 }
2195 #endif
2196
2197 /*
2198  * This mmap-allocator allocates new areas top-down from below the
2199  * stack's low limit (the base):
2200  */
2201 #ifndef HAVE_ARCH_UNMAPPED_AREA_TOPDOWN
2202 unsigned long
2203 arch_get_unmapped_area_topdown(struct file *filp, unsigned long addr,
2204                           unsigned long len, unsigned long pgoff,
2205                           unsigned long flags)
2206 {
2207         struct vm_area_struct *vma, *prev;
2208         struct mm_struct *mm = current->mm;
2209         struct vm_unmapped_area_info info;
2210         const unsigned long mmap_end = arch_get_mmap_end(addr);
2211
2212         /* requested length too big for entire address space */
2213         if (len > mmap_end - mmap_min_addr)
2214                 return -ENOMEM;
2215
2216         if (flags & MAP_FIXED)
2217                 return addr;
2218
2219         /* requesting a specific address */
2220         if (addr) {
2221                 addr = PAGE_ALIGN(addr);
2222                 vma = find_vma_prev(mm, addr, &prev);
2223                 if (mmap_end - len >= addr && addr >= mmap_min_addr &&
2224                                 (!vma || addr + len <= vm_start_gap(vma)) &&
2225                                 (!prev || addr >= vm_end_gap(prev)))
2226                         return addr;
2227         }
2228
2229         info.flags = VM_UNMAPPED_AREA_TOPDOWN;
2230         info.length = len;
2231         info.low_limit = max(PAGE_SIZE, mmap_min_addr);
2232         info.high_limit = arch_get_mmap_base(addr, mm->mmap_base);
2233         info.align_mask = 0;
2234         info.align_offset = 0;
2235         addr = vm_unmapped_area(&info);
2236
2237         /*
2238          * A failed mmap() very likely causes application failure,
2239          * so fall back to the bottom-up function here. This scenario
2240          * can happen with large stack limits and large mmap()
2241          * allocations.
2242          */
2243         if (offset_in_page(addr)) {
2244                 VM_BUG_ON(addr != -ENOMEM);
2245                 info.flags = 0;
2246                 info.low_limit = TASK_UNMAPPED_BASE;
2247                 info.high_limit = mmap_end;
2248                 addr = vm_unmapped_area(&info);
2249         }
2250
2251         return addr;
2252 }
2253 #endif
2254
2255 unsigned long
2256 get_unmapped_area(struct file *file, unsigned long addr, unsigned long len,
2257                 unsigned long pgoff, unsigned long flags)
2258 {
2259         unsigned long (*get_area)(struct file *, unsigned long,
2260                                   unsigned long, unsigned long, unsigned long);
2261
2262         unsigned long error = arch_mmap_check(addr, len, flags);
2263         if (error)
2264                 return error;
2265
2266         /* Careful about overflows.. */
2267         if (len > TASK_SIZE)
2268                 return -ENOMEM;
2269
2270         get_area = current->mm->get_unmapped_area;
2271         if (file) {
2272                 if (file->f_op->get_unmapped_area)
2273                         get_area = file->f_op->get_unmapped_area;
2274         } else if (flags & MAP_SHARED) {
2275                 /*
2276                  * mmap_region() will call shmem_zero_setup() to create a file,
2277                  * so use shmem's get_unmapped_area in case it can be huge.
2278                  * do_mmap() will clear pgoff, so match alignment.
2279                  */
2280                 pgoff = 0;
2281                 get_area = shmem_get_unmapped_area;
2282         }
2283
2284         addr = get_area(file, addr, len, pgoff, flags);
2285         if (IS_ERR_VALUE(addr))
2286                 return addr;
2287
2288         if (addr > TASK_SIZE - len)
2289                 return -ENOMEM;
2290         if (offset_in_page(addr))
2291                 return -EINVAL;
2292
2293         error = security_mmap_addr(addr);
2294         return error ? error : addr;
2295 }
2296
2297 EXPORT_SYMBOL(get_unmapped_area);
2298
2299 /* Look up the first VMA which satisfies  addr < vm_end,  NULL if none. */
2300 struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
2301 {
2302         struct rb_node *rb_node;
2303         struct vm_area_struct *vma;
2304
2305         /* Check the cache first. */
2306         vma = vmacache_find(mm, addr);
2307         if (likely(vma))
2308                 return vma;
2309
2310         rb_node = mm->mm_rb.rb_node;
2311
2312         while (rb_node) {
2313                 struct vm_area_struct *tmp;
2314
2315                 tmp = rb_entry(rb_node, struct vm_area_struct, vm_rb);
2316
2317                 if (tmp->vm_end > addr) {
2318                         vma = tmp;
2319                         if (tmp->vm_start <= addr)
2320                                 break;
2321                         rb_node = rb_node->rb_left;
2322                 } else
2323                         rb_node = rb_node->rb_right;
2324         }
2325
2326         if (vma)
2327                 vmacache_update(addr, vma);
2328         return vma;
2329 }
2330
2331 EXPORT_SYMBOL(find_vma);
2332
2333 /*
2334  * Same as find_vma, but also return a pointer to the previous VMA in *pprev.
2335  */
2336 struct vm_area_struct *
2337 find_vma_prev(struct mm_struct *mm, unsigned long addr,
2338                         struct vm_area_struct **pprev)
2339 {
2340         struct vm_area_struct *vma;
2341
2342         vma = find_vma(mm, addr);
2343         if (vma) {
2344                 *pprev = vma->vm_prev;
2345         } else {
2346                 struct rb_node *rb_node = rb_last(&mm->mm_rb);
2347
2348                 *pprev = rb_node ? rb_entry(rb_node, struct vm_area_struct, vm_rb) : NULL;
2349         }
2350         return vma;
2351 }
2352
2353 /*
2354  * Verify that the stack growth is acceptable and
2355  * update accounting. This is shared with both the
2356  * grow-up and grow-down cases.
2357  */
2358 static int acct_stack_growth(struct vm_area_struct *vma,
2359                              unsigned long size, unsigned long grow)
2360 {
2361         struct mm_struct *mm = vma->vm_mm;
2362         unsigned long new_start;
2363
2364         /* address space limit tests */
2365         if (!may_expand_vm(mm, vma->vm_flags, grow))
2366                 return -ENOMEM;
2367
2368         /* Stack limit test */
2369         if (size > rlimit(RLIMIT_STACK))
2370                 return -ENOMEM;
2371
2372         /* mlock limit tests */
2373         if (vma->vm_flags & VM_LOCKED) {
2374                 unsigned long locked;
2375                 unsigned long limit;
2376                 locked = mm->locked_vm + grow;
2377                 limit = rlimit(RLIMIT_MEMLOCK);
2378                 limit >>= PAGE_SHIFT;
2379                 if (locked > limit && !capable(CAP_IPC_LOCK))
2380                         return -ENOMEM;
2381         }
2382
2383         /* Check to ensure the stack will not grow into a hugetlb-only region */
2384         new_start = (vma->vm_flags & VM_GROWSUP) ? vma->vm_start :
2385                         vma->vm_end - size;
2386         if (is_hugepage_only_range(vma->vm_mm, new_start, size))
2387                 return -EFAULT;
2388
2389         /*
2390          * Overcommit..  This must be the final test, as it will
2391          * update security statistics.
2392          */
2393         if (security_vm_enough_memory_mm(mm, grow))
2394                 return -ENOMEM;
2395
2396         return 0;
2397 }
2398
2399 #if defined(CONFIG_STACK_GROWSUP) || defined(CONFIG_IA64)
2400 /*
2401  * PA-RISC uses this for its stack; IA64 for its Register Backing Store.
2402  * vma is the last one with address > vma->vm_end.  Have to extend vma.
2403  */
2404 int expand_upwards(struct vm_area_struct *vma, unsigned long address)
2405 {
2406         struct mm_struct *mm = vma->vm_mm;
2407         struct vm_area_struct *next;
2408         unsigned long gap_addr;
2409         int error = 0;
2410
2411         if (!(vma->vm_flags & VM_GROWSUP))
2412                 return -EFAULT;
2413
2414         /* Guard against exceeding limits of the address space. */
2415         address &= PAGE_MASK;
2416         if (address >= (TASK_SIZE & PAGE_MASK))
2417                 return -ENOMEM;
2418         address += PAGE_SIZE;
2419
2420         /* Enforce stack_guard_gap */
2421         gap_addr = address + stack_guard_gap;
2422
2423         /* Guard against overflow */
2424         if (gap_addr < address || gap_addr > TASK_SIZE)
2425                 gap_addr = TASK_SIZE;
2426
2427         next = vma->vm_next;
2428         if (next && next->vm_start < gap_addr && vma_is_accessible(next)) {
2429                 if (!(next->vm_flags & VM_GROWSUP))
2430                         return -ENOMEM;
2431                 /* Check that both stack segments have the same anon_vma? */
2432         }
2433
2434         /* We must make sure the anon_vma is allocated. */
2435         if (unlikely(anon_vma_prepare(vma)))
2436                 return -ENOMEM;
2437
2438         /*
2439          * vma->vm_start/vm_end cannot change under us because the caller
2440          * is required to hold the mmap_lock in read mode.  We need the
2441          * anon_vma lock to serialize against concurrent expand_stacks.
2442          */
2443         anon_vma_lock_write(vma->anon_vma);
2444
2445         /* Somebody else might have raced and expanded it already */
2446         if (address > vma->vm_end) {
2447                 unsigned long size, grow;
2448
2449                 size = address - vma->vm_start;
2450                 grow = (address - vma->vm_end) >> PAGE_SHIFT;
2451
2452                 error = -ENOMEM;
2453                 if (vma->vm_pgoff + (size >> PAGE_SHIFT) >= vma->vm_pgoff) {
2454                         error = acct_stack_growth(vma, size, grow);
2455                         if (!error) {
2456                                 /*
2457                                  * vma_gap_update() doesn't support concurrent
2458                                  * updates, but we only hold a shared mmap_lock
2459                                  * lock here, so we need to protect against
2460                                  * concurrent vma expansions.
2461                                  * anon_vma_lock_write() doesn't help here, as
2462                                  * we don't guarantee that all growable vmas
2463                                  * in a mm share the same root anon vma.
2464                                  * So, we reuse mm->page_table_lock to guard
2465                                  * against concurrent vma expansions.
2466                                  */
2467                                 spin_lock(&mm->page_table_lock);
2468                                 if (vma->vm_flags & VM_LOCKED)
2469                                         mm->locked_vm += grow;
2470                                 vm_stat_account(mm, vma->vm_flags, grow);
2471                                 anon_vma_interval_tree_pre_update_vma(vma);
2472                                 vma->vm_end = address;
2473                                 anon_vma_interval_tree_post_update_vma(vma);
2474                                 if (vma->vm_next)
2475                                         vma_gap_update(vma->vm_next);
2476                                 else
2477                                         mm->highest_vm_end = vm_end_gap(vma);
2478                                 spin_unlock(&mm->page_table_lock);
2479
2480                                 perf_event_mmap(vma);
2481                         }
2482                 }
2483         }
2484         anon_vma_unlock_write(vma->anon_vma);
2485         khugepaged_enter_vma_merge(vma, vma->vm_flags);
2486         validate_mm(mm);
2487         return error;
2488 }
2489 #endif /* CONFIG_STACK_GROWSUP || CONFIG_IA64 */
2490
2491 /*
2492  * vma is the first one with address < vma->vm_start.  Have to extend vma.
2493  */
2494 int expand_downwards(struct vm_area_struct *vma,
2495                                    unsigned long address)
2496 {
2497         struct mm_struct *mm = vma->vm_mm;
2498         struct vm_area_struct *prev;
2499         int error = 0;
2500
2501         address &= PAGE_MASK;
2502         if (address < mmap_min_addr)
2503                 return -EPERM;
2504
2505         /* Enforce stack_guard_gap */
2506         prev = vma->vm_prev;
2507         /* Check that both stack segments have the same anon_vma? */
2508         if (prev && !(prev->vm_flags & VM_GROWSDOWN) &&
2509                         vma_is_accessible(prev)) {
2510                 if (address - prev->vm_end < stack_guard_gap)
2511                         return -ENOMEM;
2512         }
2513
2514         /* We must make sure the anon_vma is allocated. */
2515         if (unlikely(anon_vma_prepare(vma)))
2516                 return -ENOMEM;
2517
2518         /*
2519          * vma->vm_start/vm_end cannot change under us because the caller
2520          * is required to hold the mmap_lock in read mode.  We need the
2521          * anon_vma lock to serialize against concurrent expand_stacks.
2522          */
2523         anon_vma_lock_write(vma->anon_vma);
2524
2525         /* Somebody else might have raced and expanded it already */
2526         if (address < vma->vm_start) {
2527                 unsigned long size, grow;
2528
2529                 size = vma->vm_end - address;
2530                 grow = (vma->vm_start - address) >> PAGE_SHIFT;
2531
2532                 error = -ENOMEM;
2533                 if (grow <= vma->vm_pgoff) {
2534                         error = acct_stack_growth(vma, size, grow);
2535                         if (!error) {
2536                                 /*
2537                                  * vma_gap_update() doesn't support concurrent
2538                                  * updates, but we only hold a shared mmap_lock
2539                                  * lock here, so we need to protect against
2540                                  * concurrent vma expansions.
2541                                  * anon_vma_lock_write() doesn't help here, as
2542                                  * we don't guarantee that all growable vmas
2543                                  * in a mm share the same root anon vma.
2544                                  * So, we reuse mm->page_table_lock to guard
2545                                  * against concurrent vma expansions.
2546                                  */
2547                                 spin_lock(&mm->page_table_lock);
2548                                 if (vma->vm_flags & VM_LOCKED)
2549                                         mm->locked_vm += grow;
2550                                 vm_stat_account(mm, vma->vm_flags, grow);
2551                                 anon_vma_interval_tree_pre_update_vma(vma);
2552                                 vma->vm_start = address;
2553                                 vma->vm_pgoff -= grow;
2554                                 anon_vma_interval_tree_post_update_vma(vma);
2555                                 vma_gap_update(vma);
2556                                 spin_unlock(&mm->page_table_lock);
2557
2558                                 perf_event_mmap(vma);
2559                         }
2560                 }
2561         }
2562         anon_vma_unlock_write(vma->anon_vma);
2563         khugepaged_enter_vma_merge(vma, vma->vm_flags);
2564         validate_mm(mm);
2565         return error;
2566 }
2567
2568 /* enforced gap between the expanding stack and other mappings. */
2569 unsigned long stack_guard_gap = 256UL<<PAGE_SHIFT;
2570
2571 static int __init cmdline_parse_stack_guard_gap(char *p)
2572 {
2573         unsigned long val;
2574         char *endptr;
2575
2576         val = simple_strtoul(p, &endptr, 10);
2577         if (!*endptr)
2578                 stack_guard_gap = val << PAGE_SHIFT;
2579
2580         return 0;
2581 }
2582 __setup("stack_guard_gap=", cmdline_parse_stack_guard_gap);
2583
2584 #ifdef CONFIG_STACK_GROWSUP
2585 int expand_stack(struct vm_area_struct *vma, unsigned long address)
2586 {
2587         return expand_upwards(vma, address);
2588 }
2589
2590 struct vm_area_struct *
2591 find_extend_vma(struct mm_struct *mm, unsigned long addr)
2592 {
2593         struct vm_area_struct *vma, *prev;
2594
2595         addr &= PAGE_MASK;
2596         vma = find_vma_prev(mm, addr, &prev);
2597         if (vma && (vma->vm_start <= addr))
2598                 return vma;
2599         /* don't alter vm_end if the coredump is running */
2600         if (!prev || expand_stack(prev, addr))
2601                 return NULL;
2602         if (prev->vm_flags & VM_LOCKED)
2603                 populate_vma_page_range(prev, addr, prev->vm_end, NULL);
2604         return prev;
2605 }
2606 #else
2607 int expand_stack(struct vm_area_struct *vma, unsigned long address)
2608 {
2609         return expand_downwards(vma, address);
2610 }
2611
2612 struct vm_area_struct *
2613 find_extend_vma(struct mm_struct *mm, unsigned long addr)
2614 {
2615         struct vm_area_struct *vma;
2616         unsigned long start;
2617
2618         addr &= PAGE_MASK;
2619         vma = find_vma(mm, addr);
2620         if (!vma)
2621                 return NULL;
2622         if (vma->vm_start <= addr)
2623                 return vma;
2624         if (!(vma->vm_flags & VM_GROWSDOWN))
2625                 return NULL;
2626         start = vma->vm_start;
2627         if (expand_stack(vma, addr))
2628                 return NULL;
2629         if (vma->vm_flags & VM_LOCKED)
2630                 populate_vma_page_range(vma, addr, start, NULL);
2631         return vma;
2632 }
2633 #endif
2634
2635 EXPORT_SYMBOL_GPL(find_extend_vma);
2636
2637 /*
2638  * Ok - we have the memory areas we should free on the vma list,
2639  * so release them, and do the vma updates.
2640  *
2641  * Called with the mm semaphore held.
2642  */
2643 static void remove_vma_list(struct mm_struct *mm, struct vm_area_struct *vma)
2644 {
2645         unsigned long nr_accounted = 0;
2646
2647         /* Update high watermark before we lower total_vm */
2648         update_hiwater_vm(mm);
2649         do {
2650                 long nrpages = vma_pages(vma);
2651
2652                 if (vma->vm_flags & VM_ACCOUNT)
2653                         nr_accounted += nrpages;
2654                 vm_stat_account(mm, vma->vm_flags, -nrpages);
2655                 vma = remove_vma(vma);
2656         } while (vma);
2657         vm_unacct_memory(nr_accounted);
2658         validate_mm(mm);
2659 }
2660
2661 /*
2662  * Get rid of page table information in the indicated region.
2663  *
2664  * Called with the mm semaphore held.
2665  */
2666 static void unmap_region(struct mm_struct *mm,
2667                 struct vm_area_struct *vma, struct vm_area_struct *prev,
2668                 unsigned long start, unsigned long end)
2669 {
2670         struct vm_area_struct *next = vma_next(mm, prev);
2671         struct mmu_gather tlb;
2672
2673         lru_add_drain();
2674         tlb_gather_mmu(&tlb, mm, start, end);
2675         update_hiwater_rss(mm);
2676         unmap_vmas(&tlb, vma, start, end);
2677         free_pgtables(&tlb, vma, prev ? prev->vm_end : FIRST_USER_ADDRESS,
2678                                  next ? next->vm_start : USER_PGTABLES_CEILING);
2679         tlb_finish_mmu(&tlb, start, end);
2680 }
2681
2682 /*
2683  * Create a list of vma's touched by the unmap, removing them from the mm's
2684  * vma list as we go..
2685  */
2686 static bool
2687 detach_vmas_to_be_unmapped(struct mm_struct *mm, struct vm_area_struct *vma,
2688         struct vm_area_struct *prev, unsigned long end)
2689 {
2690         struct vm_area_struct **insertion_point;
2691         struct vm_area_struct *tail_vma = NULL;
2692
2693         insertion_point = (prev ? &prev->vm_next : &mm->mmap);
2694         vma->vm_prev = NULL;
2695         do {
2696                 vma_rb_erase(vma, &mm->mm_rb);
2697                 mm->map_count--;
2698                 tail_vma = vma;
2699                 vma = vma->vm_next;
2700         } while (vma && vma->vm_start < end);
2701         *insertion_point = vma;
2702         if (vma) {
2703                 vma->vm_prev = prev;
2704                 vma_gap_update(vma);
2705         } else
2706                 mm->highest_vm_end = prev ? vm_end_gap(prev) : 0;
2707         tail_vma->vm_next = NULL;
2708
2709         /* Kill the cache */
2710         vmacache_invalidate(mm);
2711
2712         /*
2713          * Do not downgrade mmap_lock if we are next to VM_GROWSDOWN or
2714          * VM_GROWSUP VMA. Such VMAs can change their size under
2715          * down_read(mmap_lock) and collide with the VMA we are about to unmap.
2716          */
2717         if (vma && (vma->vm_flags & VM_GROWSDOWN))
2718                 return false;
2719         if (prev && (prev->vm_flags & VM_GROWSUP))
2720                 return false;
2721         return true;
2722 }
2723
2724 /*
2725  * __split_vma() bypasses sysctl_max_map_count checking.  We use this where it
2726  * has already been checked or doesn't make sense to fail.
2727  */
2728 int __split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
2729                 unsigned long addr, int new_below)
2730 {
2731         struct vm_area_struct *new;
2732         int err;
2733
2734         if (vma->vm_ops && vma->vm_ops->split) {
2735                 err = vma->vm_ops->split(vma, addr);
2736                 if (err)
2737                         return err;
2738         }
2739
2740         new = vm_area_dup(vma);
2741         if (!new)
2742                 return -ENOMEM;
2743
2744         if (new_below)
2745                 new->vm_end = addr;
2746         else {
2747                 new->vm_start = addr;
2748                 new->vm_pgoff += ((addr - vma->vm_start) >> PAGE_SHIFT);
2749         }
2750
2751         err = vma_dup_policy(vma, new);
2752         if (err)
2753                 goto out_free_vma;
2754
2755         err = anon_vma_clone(new, vma);
2756         if (err)
2757                 goto out_free_mpol;
2758
2759         if (new->vm_file)
2760                 get_file(new->vm_file);
2761
2762         if (new->vm_ops && new->vm_ops->open)
2763                 new->vm_ops->open(new);
2764
2765         if (new_below)
2766                 err = vma_adjust(vma, addr, vma->vm_end, vma->vm_pgoff +
2767                         ((addr - new->vm_start) >> PAGE_SHIFT), new);
2768         else
2769                 err = vma_adjust(vma, vma->vm_start, addr, vma->vm_pgoff, new);
2770
2771         /* Success. */
2772         if (!err)
2773                 return 0;
2774
2775         /* Clean everything up if vma_adjust failed. */
2776         if (new->vm_ops && new->vm_ops->close)
2777                 new->vm_ops->close(new);
2778         if (new->vm_file)
2779                 fput(new->vm_file);
2780         unlink_anon_vmas(new);
2781  out_free_mpol:
2782         mpol_put(vma_policy(new));
2783  out_free_vma:
2784         vm_area_free(new);
2785         return err;
2786 }
2787
2788 /*
2789  * Split a vma into two pieces at address 'addr', a new vma is allocated
2790  * either for the first part or the tail.
2791  */
2792 int split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
2793               unsigned long addr, int new_below)
2794 {
2795         if (mm->map_count >= sysctl_max_map_count)
2796                 return -ENOMEM;
2797
2798         return __split_vma(mm, vma, addr, new_below);
2799 }
2800
2801 /* Munmap is split into 2 main parts -- this part which finds
2802  * what needs doing, and the areas themselves, which do the
2803  * work.  This now handles partial unmappings.
2804  * Jeremy Fitzhardinge <jeremy@goop.org>
2805  */
2806 int __do_munmap(struct mm_struct *mm, unsigned long start, size_t len,
2807                 struct list_head *uf, bool downgrade)
2808 {
2809         unsigned long end;
2810         struct vm_area_struct *vma, *prev, *last;
2811
2812         if ((offset_in_page(start)) || start > TASK_SIZE || len > TASK_SIZE-start)
2813                 return -EINVAL;
2814
2815         len = PAGE_ALIGN(len);
2816         end = start + len;
2817         if (len == 0)
2818                 return -EINVAL;
2819
2820         /*
2821          * arch_unmap() might do unmaps itself.  It must be called
2822          * and finish any rbtree manipulation before this code
2823          * runs and also starts to manipulate the rbtree.
2824          */
2825         arch_unmap(mm, start, end);
2826
2827         /* Find the first overlapping VMA */
2828         vma = find_vma(mm, start);
2829         if (!vma)
2830                 return 0;
2831         prev = vma->vm_prev;
2832         /* we have  start < vma->vm_end  */
2833
2834         /* if it doesn't overlap, we have nothing.. */
2835         if (vma->vm_start >= end)
2836                 return 0;
2837
2838         /*
2839          * If we need to split any vma, do it now to save pain later.
2840          *
2841          * Note: mremap's move_vma VM_ACCOUNT handling assumes a partially
2842          * unmapped vm_area_struct will remain in use: so lower split_vma
2843          * places tmp vma above, and higher split_vma places tmp vma below.
2844          */
2845         if (start > vma->vm_start) {
2846                 int error;
2847
2848                 /*
2849                  * Make sure that map_count on return from munmap() will
2850                  * not exceed its limit; but let map_count go just above
2851                  * its limit temporarily, to help free resources as expected.
2852                  */
2853                 if (end < vma->vm_end && mm->map_count >= sysctl_max_map_count)
2854                         return -ENOMEM;
2855
2856                 error = __split_vma(mm, vma, start, 0);
2857                 if (error)
2858                         return error;
2859                 prev = vma;
2860         }
2861
2862         /* Does it split the last one? */
2863         last = find_vma(mm, end);
2864         if (last && end > last->vm_start) {
2865                 int error = __split_vma(mm, last, end, 1);
2866                 if (error)
2867                         return error;
2868         }
2869         vma = vma_next(mm, prev);
2870
2871         if (unlikely(uf)) {
2872                 /*
2873                  * If userfaultfd_unmap_prep returns an error the vmas
2874                  * will remain splitted, but userland will get a
2875                  * highly unexpected error anyway. This is no
2876                  * different than the case where the first of the two
2877                  * __split_vma fails, but we don't undo the first
2878                  * split, despite we could. This is unlikely enough
2879                  * failure that it's not worth optimizing it for.
2880                  */
2881                 int error = userfaultfd_unmap_prep(vma, start, end, uf);
2882                 if (error)
2883                         return error;
2884         }
2885
2886         /*
2887          * unlock any mlock()ed ranges before detaching vmas
2888          */
2889         if (mm->locked_vm) {
2890                 struct vm_area_struct *tmp = vma;
2891                 while (tmp && tmp->vm_start < end) {
2892                         if (tmp->vm_flags & VM_LOCKED) {
2893                                 mm->locked_vm -= vma_pages(tmp);
2894                                 munlock_vma_pages_all(tmp);
2895                         }
2896
2897                         tmp = tmp->vm_next;
2898                 }
2899         }
2900
2901         /* Detach vmas from rbtree */
2902         if (!detach_vmas_to_be_unmapped(mm, vma, prev, end))
2903                 downgrade = false;
2904
2905         if (downgrade)
2906                 mmap_write_downgrade(mm);
2907
2908         unmap_region(mm, vma, prev, start, end);
2909
2910         /* Fix up all other VM information */
2911         remove_vma_list(mm, vma);
2912
2913         return downgrade ? 1 : 0;
2914 }
2915
2916 int do_munmap(struct mm_struct *mm, unsigned long start, size_t len,
2917               struct list_head *uf)
2918 {
2919         return __do_munmap(mm, start, len, uf, false);
2920 }
2921
2922 static int __vm_munmap(unsigned long start, size_t len, bool downgrade)
2923 {
2924         int ret;
2925         struct mm_struct *mm = current->mm;
2926         LIST_HEAD(uf);
2927
2928         if (mmap_write_lock_killable(mm))
2929                 return -EINTR;
2930
2931         ret = __do_munmap(mm, start, len, &uf, downgrade);
2932         /*
2933          * Returning 1 indicates mmap_lock is downgraded.
2934          * But 1 is not legal return value of vm_munmap() and munmap(), reset
2935          * it to 0 before return.
2936          */
2937         if (ret == 1) {
2938                 mmap_read_unlock(mm);
2939                 ret = 0;
2940         } else
2941                 mmap_write_unlock(mm);
2942
2943         userfaultfd_unmap_complete(mm, &uf);
2944         return ret;
2945 }
2946
2947 int vm_munmap(unsigned long start, size_t len)
2948 {
2949         return __vm_munmap(start, len, false);
2950 }
2951 EXPORT_SYMBOL(vm_munmap);
2952
2953 SYSCALL_DEFINE2(munmap, unsigned long, addr, size_t, len)
2954 {
2955         addr = untagged_addr(addr);
2956         profile_munmap(addr);
2957         return __vm_munmap(addr, len, true);
2958 }
2959
2960
2961 /*
2962  * Emulation of deprecated remap_file_pages() syscall.
2963  */
2964 SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size,
2965                 unsigned long, prot, unsigned long, pgoff, unsigned long, flags)
2966 {
2967
2968         struct mm_struct *mm = current->mm;
2969         struct vm_area_struct *vma;
2970         unsigned long populate = 0;
2971         unsigned long ret = -EINVAL;
2972         struct file *file;
2973
2974         pr_warn_once("%s (%d) uses deprecated remap_file_pages() syscall. See Documentation/vm/remap_file_pages.rst.\n",
2975                      current->comm, current->pid);
2976
2977         if (prot)
2978                 return ret;
2979         start = start & PAGE_MASK;
2980         size = size & PAGE_MASK;
2981
2982         if (start + size <= start)
2983                 return ret;
2984
2985         /* Does pgoff wrap? */
2986         if (pgoff + (size >> PAGE_SHIFT) < pgoff)
2987                 return ret;
2988
2989         if (mmap_write_lock_killable(mm))
2990                 return -EINTR;
2991
2992         vma = find_vma(mm, start);
2993
2994         if (!vma || !(vma->vm_flags & VM_SHARED))
2995                 goto out;
2996
2997         if (start < vma->vm_start)
2998                 goto out;
2999
3000         if (start + size > vma->vm_end) {
3001                 struct vm_area_struct *next;
3002
3003                 for (next = vma->vm_next; next; next = next->vm_next) {
3004                         /* hole between vmas ? */
3005                         if (next->vm_start != next->vm_prev->vm_end)
3006                                 goto out;
3007
3008                         if (next->vm_file != vma->vm_file)
3009                                 goto out;
3010
3011                         if (next->vm_flags != vma->vm_flags)
3012                                 goto out;
3013
3014                         if (start + size <= next->vm_end)
3015                                 break;
3016                 }
3017
3018                 if (!next)
3019                         goto out;
3020         }
3021
3022         prot |= vma->vm_flags & VM_READ ? PROT_READ : 0;
3023         prot |= vma->vm_flags & VM_WRITE ? PROT_WRITE : 0;
3024         prot |= vma->vm_flags & VM_EXEC ? PROT_EXEC : 0;
3025
3026         flags &= MAP_NONBLOCK;
3027         flags |= MAP_SHARED | MAP_FIXED | MAP_POPULATE;
3028         if (vma->vm_flags & VM_LOCKED) {
3029                 struct vm_area_struct *tmp;
3030                 flags |= MAP_LOCKED;
3031
3032                 /* drop PG_Mlocked flag for over-mapped range */
3033                 for (tmp = vma; tmp->vm_start >= start + size;
3034                                 tmp = tmp->vm_next) {
3035                         /*
3036                          * Split pmd and munlock page on the border
3037                          * of the range.
3038                          */
3039                         vma_adjust_trans_huge(tmp, start, start + size, 0);
3040
3041                         munlock_vma_pages_range(tmp,
3042                                         max(tmp->vm_start, start),
3043                                         min(tmp->vm_end, start + size));
3044                 }
3045         }
3046
3047         file = get_file(vma->vm_file);
3048         ret = do_mmap(vma->vm_file, start, size,
3049                         prot, flags, pgoff, &populate, NULL);
3050         fput(file);
3051 out:
3052         mmap_write_unlock(mm);
3053         if (populate)
3054                 mm_populate(ret, populate);
3055         if (!IS_ERR_VALUE(ret))
3056                 ret = 0;
3057         return ret;
3058 }
3059
3060 /*
3061  *  this is really a simplified "do_mmap".  it only handles
3062  *  anonymous maps.  eventually we may be able to do some
3063  *  brk-specific accounting here.
3064  */
3065 static int do_brk_flags(unsigned long addr, unsigned long len, unsigned long flags, struct list_head *uf)
3066 {
3067         struct mm_struct *mm = current->mm;
3068         struct vm_area_struct *vma, *prev;
3069         struct rb_node **rb_link, *rb_parent;
3070         pgoff_t pgoff = addr >> PAGE_SHIFT;
3071         int error;
3072         unsigned long mapped_addr;
3073
3074         /* Until we need other flags, refuse anything except VM_EXEC. */
3075         if ((flags & (~VM_EXEC)) != 0)
3076                 return -EINVAL;
3077         flags |= VM_DATA_DEFAULT_FLAGS | VM_ACCOUNT | mm->def_flags;
3078
3079         mapped_addr = get_unmapped_area(NULL, addr, len, 0, MAP_FIXED);
3080         if (IS_ERR_VALUE(mapped_addr))
3081                 return mapped_addr;
3082
3083         error = mlock_future_check(mm, mm->def_flags, len);
3084         if (error)
3085                 return error;
3086
3087         /* Clear old maps, set up prev, rb_link, rb_parent, and uf */
3088         if (munmap_vma_range(mm, addr, len, &prev, &rb_link, &rb_parent, uf))
3089                 return -ENOMEM;
3090
3091         /* Check against address space limits *after* clearing old maps... */
3092         if (!may_expand_vm(mm, flags, len >> PAGE_SHIFT))
3093                 return -ENOMEM;
3094
3095         if (mm->map_count > sysctl_max_map_count)
3096                 return -ENOMEM;
3097
3098         if (security_vm_enough_memory_mm(mm, len >> PAGE_SHIFT))
3099                 return -ENOMEM;
3100
3101         /* Can we just expand an old private anonymous mapping? */
3102         vma = vma_merge(mm, prev, addr, addr + len, flags,
3103                         NULL, NULL, pgoff, NULL, NULL_VM_UFFD_CTX);
3104         if (vma)
3105                 goto out;
3106
3107         /*
3108          * create a vma struct for an anonymous mapping
3109          */
3110         vma = vm_area_alloc(mm);
3111         if (!vma) {
3112                 vm_unacct_memory(len >> PAGE_SHIFT);
3113                 return -ENOMEM;
3114         }
3115
3116         vma_set_anonymous(vma);
3117         vma->vm_start = addr;
3118         vma->vm_end = addr + len;
3119         vma->vm_pgoff = pgoff;
3120         vma->vm_flags = flags;
3121         vma->vm_page_prot = vm_get_page_prot(flags);
3122         vma_link(mm, vma, prev, rb_link, rb_parent);
3123 out:
3124         perf_event_mmap(vma);
3125         mm->total_vm += len >> PAGE_SHIFT;
3126         mm->data_vm += len >> PAGE_SHIFT;
3127         if (flags & VM_LOCKED)
3128                 mm->locked_vm += (len >> PAGE_SHIFT);
3129         vma->vm_flags |= VM_SOFTDIRTY;
3130         return 0;
3131 }
3132
3133 int vm_brk_flags(unsigned long addr, unsigned long request, unsigned long flags)
3134 {
3135         struct mm_struct *mm = current->mm;
3136         unsigned long len;
3137         int ret;
3138         bool populate;
3139         LIST_HEAD(uf);
3140
3141         len = PAGE_ALIGN(request);
3142         if (len < request)
3143                 return -ENOMEM;
3144         if (!len)
3145                 return 0;
3146
3147         if (mmap_write_lock_killable(mm))
3148                 return -EINTR;
3149
3150         ret = do_brk_flags(addr, len, flags, &uf);
3151         populate = ((mm->def_flags & VM_LOCKED) != 0);
3152         mmap_write_unlock(mm);
3153         userfaultfd_unmap_complete(mm, &uf);
3154         if (populate && !ret)
3155                 mm_populate(addr, len);
3156         return ret;
3157 }
3158 EXPORT_SYMBOL(vm_brk_flags);
3159
3160 int vm_brk(unsigned long addr, unsigned long len)
3161 {
3162         return vm_brk_flags(addr, len, 0);
3163 }
3164 EXPORT_SYMBOL(vm_brk);
3165
3166 /* Release all mmaps. */
3167 void exit_mmap(struct mm_struct *mm)
3168 {
3169         struct mmu_gather tlb;
3170         struct vm_area_struct *vma;
3171         unsigned long nr_accounted = 0;
3172
3173         /* mm's last user has gone, and its about to be pulled down */
3174         mmu_notifier_release(mm);
3175
3176         if (unlikely(mm_is_oom_victim(mm))) {
3177                 /*
3178                  * Manually reap the mm to free as much memory as possible.
3179                  * Then, as the oom reaper does, set MMF_OOM_SKIP to disregard
3180                  * this mm from further consideration.  Taking mm->mmap_lock for
3181                  * write after setting MMF_OOM_SKIP will guarantee that the oom
3182                  * reaper will not run on this mm again after mmap_lock is
3183                  * dropped.
3184                  *
3185                  * Nothing can be holding mm->mmap_lock here and the above call
3186                  * to mmu_notifier_release(mm) ensures mmu notifier callbacks in
3187                  * __oom_reap_task_mm() will not block.
3188                  *
3189                  * This needs to be done before calling munlock_vma_pages_all(),
3190                  * which clears VM_LOCKED, otherwise the oom reaper cannot
3191                  * reliably test it.
3192                  */
3193                 (void)__oom_reap_task_mm(mm);
3194
3195                 set_bit(MMF_OOM_SKIP, &mm->flags);
3196                 mmap_write_lock(mm);
3197                 mmap_write_unlock(mm);
3198         }
3199
3200         if (mm->locked_vm) {
3201                 vma = mm->mmap;
3202                 while (vma) {
3203                         if (vma->vm_flags & VM_LOCKED)
3204                                 munlock_vma_pages_all(vma);
3205                         vma = vma->vm_next;
3206                 }
3207         }
3208
3209         arch_exit_mmap(mm);
3210
3211         vma = mm->mmap;
3212         if (!vma)       /* Can happen if dup_mmap() received an OOM */
3213                 return;
3214
3215         lru_add_drain();
3216         flush_cache_mm(mm);
3217         tlb_gather_mmu(&tlb, mm, 0, -1);
3218         /* update_hiwater_rss(mm) here? but nobody should be looking */
3219         /* Use -1 here to ensure all VMAs in the mm are unmapped */
3220         unmap_vmas(&tlb, vma, 0, -1);
3221         free_pgtables(&tlb, vma, FIRST_USER_ADDRESS, USER_PGTABLES_CEILING);
3222         tlb_finish_mmu(&tlb, 0, -1);
3223
3224         /*
3225          * Walk the list again, actually closing and freeing it,
3226          * with preemption enabled, without holding any MM locks.
3227          */
3228         while (vma) {
3229                 if (vma->vm_flags & VM_ACCOUNT)
3230                         nr_accounted += vma_pages(vma);
3231                 vma = remove_vma(vma);
3232                 cond_resched();
3233         }
3234         vm_unacct_memory(nr_accounted);
3235 }
3236
3237 /* Insert vm structure into process list sorted by address
3238  * and into the inode's i_mmap tree.  If vm_file is non-NULL
3239  * then i_mmap_rwsem is taken here.
3240  */
3241 int insert_vm_struct(struct mm_struct *mm, struct vm_area_struct *vma)
3242 {
3243         struct vm_area_struct *prev;
3244         struct rb_node **rb_link, *rb_parent;
3245
3246         if (find_vma_links(mm, vma->vm_start, vma->vm_end,
3247                            &prev, &rb_link, &rb_parent))
3248                 return -ENOMEM;
3249         if ((vma->vm_flags & VM_ACCOUNT) &&
3250              security_vm_enough_memory_mm(mm, vma_pages(vma)))
3251                 return -ENOMEM;
3252
3253         /*
3254          * The vm_pgoff of a purely anonymous vma should be irrelevant
3255          * until its first write fault, when page's anon_vma and index
3256          * are set.  But now set the vm_pgoff it will almost certainly
3257          * end up with (unless mremap moves it elsewhere before that
3258          * first wfault), so /proc/pid/maps tells a consistent story.
3259          *
3260          * By setting it to reflect the virtual start address of the
3261          * vma, merges and splits can happen in a seamless way, just
3262          * using the existing file pgoff checks and manipulations.
3263          * Similarly in do_mmap and in do_brk_flags.
3264          */
3265         if (vma_is_anonymous(vma)) {
3266                 BUG_ON(vma->anon_vma);
3267                 vma->vm_pgoff = vma->vm_start >> PAGE_SHIFT;
3268         }
3269
3270         vma_link(mm, vma, prev, rb_link, rb_parent);
3271         return 0;
3272 }
3273
3274 /*
3275  * Copy the vma structure to a new location in the same mm,
3276  * prior to moving page table entries, to effect an mremap move.
3277  */
3278 struct vm_area_struct *copy_vma(struct vm_area_struct **vmap,
3279         unsigned long addr, unsigned long len, pgoff_t pgoff,
3280         bool *need_rmap_locks)
3281 {
3282         struct vm_area_struct *vma = *vmap;
3283         unsigned long vma_start = vma->vm_start;
3284         struct mm_struct *mm = vma->vm_mm;
3285         struct vm_area_struct *new_vma, *prev;
3286         struct rb_node **rb_link, *rb_parent;
3287         bool faulted_in_anon_vma = true;
3288
3289         /*
3290          * If anonymous vma has not yet been faulted, update new pgoff
3291          * to match new location, to increase its chance of merging.
3292          */
3293         if (unlikely(vma_is_anonymous(vma) && !vma->anon_vma)) {
3294                 pgoff = addr >> PAGE_SHIFT;
3295                 faulted_in_anon_vma = false;
3296         }
3297
3298         if (find_vma_links(mm, addr, addr + len, &prev, &rb_link, &rb_parent))
3299                 return NULL;    /* should never get here */
3300         new_vma = vma_merge(mm, prev, addr, addr + len, vma->vm_flags,
3301                             vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma),
3302                             vma->vm_userfaultfd_ctx);
3303         if (new_vma) {
3304                 /*
3305                  * Source vma may have been merged into new_vma
3306                  */
3307                 if (unlikely(vma_start >= new_vma->vm_start &&
3308                              vma_start < new_vma->vm_end)) {
3309                         /*
3310                          * The only way we can get a vma_merge with
3311                          * self during an mremap is if the vma hasn't
3312                          * been faulted in yet and we were allowed to
3313                          * reset the dst vma->vm_pgoff to the
3314                          * destination address of the mremap to allow
3315                          * the merge to happen. mremap must change the
3316                          * vm_pgoff linearity between src and dst vmas
3317                          * (in turn preventing a vma_merge) to be
3318                          * safe. It is only safe to keep the vm_pgoff
3319                          * linear if there are no pages mapped yet.
3320                          */
3321                         VM_BUG_ON_VMA(faulted_in_anon_vma, new_vma);
3322                         *vmap = vma = new_vma;
3323                 }
3324                 *need_rmap_locks = (new_vma->vm_pgoff <= vma->vm_pgoff);
3325         } else {
3326                 new_vma = vm_area_dup(vma);
3327                 if (!new_vma)
3328                         goto out;
3329                 new_vma->vm_start = addr;
3330                 new_vma->vm_end = addr + len;
3331                 new_vma->vm_pgoff = pgoff;
3332                 if (vma_dup_policy(vma, new_vma))
3333                         goto out_free_vma;
3334                 if (anon_vma_clone(new_vma, vma))
3335                         goto out_free_mempol;
3336                 if (new_vma->vm_file)
3337                         get_file(new_vma->vm_file);
3338                 if (new_vma->vm_ops && new_vma->vm_ops->open)
3339                         new_vma->vm_ops->open(new_vma);
3340                 vma_link(mm, new_vma, prev, rb_link, rb_parent);
3341                 *need_rmap_locks = false;
3342         }
3343         return new_vma;
3344
3345 out_free_mempol:
3346         mpol_put(vma_policy(new_vma));
3347 out_free_vma:
3348         vm_area_free(new_vma);
3349 out:
3350         return NULL;
3351 }
3352
3353 /*
3354  * Return true if the calling process may expand its vm space by the passed
3355  * number of pages
3356  */
3357 bool may_expand_vm(struct mm_struct *mm, vm_flags_t flags, unsigned long npages)
3358 {
3359         if (mm->total_vm + npages > rlimit(RLIMIT_AS) >> PAGE_SHIFT)
3360                 return false;
3361
3362         if (is_data_mapping(flags) &&
3363             mm->data_vm + npages > rlimit(RLIMIT_DATA) >> PAGE_SHIFT) {
3364                 /* Workaround for Valgrind */
3365                 if (rlimit(RLIMIT_DATA) == 0 &&
3366                     mm->data_vm + npages <= rlimit_max(RLIMIT_DATA) >> PAGE_SHIFT)
3367                         return true;
3368
3369                 pr_warn_once("%s (%d): VmData %lu exceed data ulimit %lu. Update limits%s.\n",
3370                              current->comm, current->pid,
3371                              (mm->data_vm + npages) << PAGE_SHIFT,
3372                              rlimit(RLIMIT_DATA),
3373                              ignore_rlimit_data ? "" : " or use boot option ignore_rlimit_data");
3374
3375                 if (!ignore_rlimit_data)
3376                         return false;
3377         }
3378
3379         return true;
3380 }
3381
3382 void vm_stat_account(struct mm_struct *mm, vm_flags_t flags, long npages)
3383 {
3384         mm->total_vm += npages;
3385
3386         if (is_exec_mapping(flags))
3387                 mm->exec_vm += npages;
3388         else if (is_stack_mapping(flags))
3389                 mm->stack_vm += npages;
3390         else if (is_data_mapping(flags))
3391                 mm->data_vm += npages;
3392 }
3393
3394 static vm_fault_t special_mapping_fault(struct vm_fault *vmf);
3395
3396 /*
3397  * Having a close hook prevents vma merging regardless of flags.
3398  */
3399 static void special_mapping_close(struct vm_area_struct *vma)
3400 {
3401 }
3402
3403 static const char *special_mapping_name(struct vm_area_struct *vma)
3404 {
3405         return ((struct vm_special_mapping *)vma->vm_private_data)->name;
3406 }
3407
3408 static int special_mapping_mremap(struct vm_area_struct *new_vma)
3409 {
3410         struct vm_special_mapping *sm = new_vma->vm_private_data;
3411
3412         if (WARN_ON_ONCE(current->mm != new_vma->vm_mm))
3413                 return -EFAULT;
3414
3415         if (sm->mremap)
3416                 return sm->mremap(sm, new_vma);
3417
3418         return 0;
3419 }
3420
3421 static const struct vm_operations_struct special_mapping_vmops = {
3422         .close = special_mapping_close,
3423         .fault = special_mapping_fault,
3424         .mremap = special_mapping_mremap,
3425         .name = special_mapping_name,
3426         /* vDSO code relies that VVAR can't be accessed remotely */
3427         .access = NULL,
3428 };
3429
3430 static const struct vm_operations_struct legacy_special_mapping_vmops = {
3431         .close = special_mapping_close,
3432         .fault = special_mapping_fault,
3433 };
3434
3435 static vm_fault_t special_mapping_fault(struct vm_fault *vmf)
3436 {
3437         struct vm_area_struct *vma = vmf->vma;
3438         pgoff_t pgoff;
3439         struct page **pages;
3440
3441         if (vma->vm_ops == &legacy_special_mapping_vmops) {
3442                 pages = vma->vm_private_data;
3443         } else {
3444                 struct vm_special_mapping *sm = vma->vm_private_data;
3445
3446                 if (sm->fault)
3447                         return sm->fault(sm, vmf->vma, vmf);
3448
3449                 pages = sm->pages;
3450         }
3451
3452         for (pgoff = vmf->pgoff; pgoff && *pages; ++pages)
3453                 pgoff--;
3454
3455         if (*pages) {
3456                 struct page *page = *pages;
3457                 get_page(page);
3458                 vmf->page = page;
3459                 return 0;
3460         }
3461
3462         return VM_FAULT_SIGBUS;
3463 }
3464
3465 static struct vm_area_struct *__install_special_mapping(
3466         struct mm_struct *mm,
3467         unsigned long addr, unsigned long len,
3468         unsigned long vm_flags, void *priv,
3469         const struct vm_operations_struct *ops)
3470 {
3471         int ret;
3472         struct vm_area_struct *vma;
3473
3474         vma = vm_area_alloc(mm);
3475         if (unlikely(vma == NULL))
3476                 return ERR_PTR(-ENOMEM);
3477
3478         vma->vm_start = addr;
3479         vma->vm_end = addr + len;
3480
3481         vma->vm_flags = vm_flags | mm->def_flags | VM_DONTEXPAND | VM_SOFTDIRTY;
3482         vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
3483
3484         vma->vm_ops = ops;
3485         vma->vm_private_data = priv;
3486
3487         ret = insert_vm_struct(mm, vma);
3488         if (ret)
3489                 goto out;
3490
3491         vm_stat_account(mm, vma->vm_flags, len >> PAGE_SHIFT);
3492
3493         perf_event_mmap(vma);
3494
3495         return vma;
3496
3497 out:
3498         vm_area_free(vma);
3499         return ERR_PTR(ret);
3500 }
3501
3502 bool vma_is_special_mapping(const struct vm_area_struct *vma,
3503         const struct vm_special_mapping *sm)
3504 {
3505         return vma->vm_private_data == sm &&
3506                 (vma->vm_ops == &special_mapping_vmops ||
3507                  vma->vm_ops == &legacy_special_mapping_vmops);
3508 }
3509
3510 /*
3511  * Called with mm->mmap_lock held for writing.
3512  * Insert a new vma covering the given region, with the given flags.
3513  * Its pages are supplied by the given array of struct page *.
3514  * The array can be shorter than len >> PAGE_SHIFT if it's null-terminated.
3515  * The region past the last page supplied will always produce SIGBUS.
3516  * The array pointer and the pages it points to are assumed to stay alive
3517  * for as long as this mapping might exist.
3518  */
3519 struct vm_area_struct *_install_special_mapping(
3520         struct mm_struct *mm,
3521         unsigned long addr, unsigned long len,
3522         unsigned long vm_flags, const struct vm_special_mapping *spec)
3523 {
3524         return __install_special_mapping(mm, addr, len, vm_flags, (void *)spec,
3525                                         &special_mapping_vmops);
3526 }
3527
3528 int install_special_mapping(struct mm_struct *mm,
3529                             unsigned long addr, unsigned long len,
3530                             unsigned long vm_flags, struct page **pages)
3531 {
3532         struct vm_area_struct *vma = __install_special_mapping(
3533                 mm, addr, len, vm_flags, (void *)pages,
3534                 &legacy_special_mapping_vmops);
3535
3536         return PTR_ERR_OR_ZERO(vma);
3537 }
3538
3539 static DEFINE_MUTEX(mm_all_locks_mutex);
3540
3541 static void vm_lock_anon_vma(struct mm_struct *mm, struct anon_vma *anon_vma)
3542 {
3543         if (!test_bit(0, (unsigned long *) &anon_vma->root->rb_root.rb_root.rb_node)) {
3544                 /*
3545                  * The LSB of head.next can't change from under us
3546                  * because we hold the mm_all_locks_mutex.
3547                  */
3548                 down_write_nest_lock(&anon_vma->root->rwsem, &mm->mmap_lock);
3549                 /*
3550                  * We can safely modify head.next after taking the
3551                  * anon_vma->root->rwsem. If some other vma in this mm shares
3552                  * the same anon_vma we won't take it again.
3553                  *
3554                  * No need of atomic instructions here, head.next
3555                  * can't change from under us thanks to the
3556                  * anon_vma->root->rwsem.
3557                  */
3558                 if (__test_and_set_bit(0, (unsigned long *)
3559                                        &anon_vma->root->rb_root.rb_root.rb_node))
3560                         BUG();
3561         }
3562 }
3563
3564 static void vm_lock_mapping(struct mm_struct *mm, struct address_space *mapping)
3565 {
3566         if (!test_bit(AS_MM_ALL_LOCKS, &mapping->flags)) {
3567                 /*
3568                  * AS_MM_ALL_LOCKS can't change from under us because
3569                  * we hold the mm_all_locks_mutex.
3570                  *
3571                  * Operations on ->flags have to be atomic because
3572                  * even if AS_MM_ALL_LOCKS is stable thanks to the
3573                  * mm_all_locks_mutex, there may be other cpus
3574                  * changing other bitflags in parallel to us.
3575                  */
3576                 if (test_and_set_bit(AS_MM_ALL_LOCKS, &mapping->flags))
3577                         BUG();
3578                 down_write_nest_lock(&mapping->i_mmap_rwsem, &mm->mmap_lock);
3579         }
3580 }
3581
3582 /*
3583  * This operation locks against the VM for all pte/vma/mm related
3584  * operations that could ever happen on a certain mm. This includes
3585  * vmtruncate, try_to_unmap, and all page faults.
3586  *
3587  * The caller must take the mmap_lock in write mode before calling
3588  * mm_take_all_locks(). The caller isn't allowed to release the
3589  * mmap_lock until mm_drop_all_locks() returns.
3590  *
3591  * mmap_lock in write mode is required in order to block all operations
3592  * that could modify pagetables and free pages without need of
3593  * altering the vma layout. It's also needed in write mode to avoid new
3594  * anon_vmas to be associated with existing vmas.
3595  *
3596  * A single task can't take more than one mm_take_all_locks() in a row
3597  * or it would deadlock.
3598  *
3599  * The LSB in anon_vma->rb_root.rb_node and the AS_MM_ALL_LOCKS bitflag in
3600  * mapping->flags avoid to take the same lock twice, if more than one
3601  * vma in this mm is backed by the same anon_vma or address_space.
3602  *
3603  * We take locks in following order, accordingly to comment at beginning
3604  * of mm/rmap.c:
3605  *   - all hugetlbfs_i_mmap_rwsem_key locks (aka mapping->i_mmap_rwsem for
3606  *     hugetlb mapping);
3607  *   - all i_mmap_rwsem locks;
3608  *   - all anon_vma->rwseml
3609  *
3610  * We can take all locks within these types randomly because the VM code
3611  * doesn't nest them and we protected from parallel mm_take_all_locks() by
3612  * mm_all_locks_mutex.
3613  *
3614  * mm_take_all_locks() and mm_drop_all_locks are expensive operations
3615  * that may have to take thousand of locks.
3616  *
3617  * mm_take_all_locks() can fail if it's interrupted by signals.
3618  */
3619 int mm_take_all_locks(struct mm_struct *mm)
3620 {
3621         struct vm_area_struct *vma;
3622         struct anon_vma_chain *avc;
3623
3624         BUG_ON(mmap_read_trylock(mm));
3625
3626         mutex_lock(&mm_all_locks_mutex);
3627
3628         for (vma = mm->mmap; vma; vma = vma->vm_next) {
3629                 if (signal_pending(current))
3630                         goto out_unlock;
3631                 if (vma->vm_file && vma->vm_file->f_mapping &&
3632                                 is_vm_hugetlb_page(vma))
3633                         vm_lock_mapping(mm, vma->vm_file->f_mapping);
3634         }
3635
3636         for (vma = mm->mmap; vma; vma = vma->vm_next) {
3637                 if (signal_pending(current))
3638                         goto out_unlock;
3639                 if (vma->vm_file && vma->vm_file->f_mapping &&
3640                                 !is_vm_hugetlb_page(vma))
3641                         vm_lock_mapping(mm, vma->vm_file->f_mapping);
3642         }
3643
3644         for (vma = mm->mmap; vma; vma = vma->vm_next) {
3645                 if (signal_pending(current))
3646                         goto out_unlock;
3647                 if (vma->anon_vma)
3648                         list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
3649                                 vm_lock_anon_vma(mm, avc->anon_vma);
3650         }
3651
3652         return 0;
3653
3654 out_unlock:
3655         mm_drop_all_locks(mm);
3656         return -EINTR;
3657 }
3658
3659 static void vm_unlock_anon_vma(struct anon_vma *anon_vma)
3660 {
3661         if (test_bit(0, (unsigned long *) &anon_vma->root->rb_root.rb_root.rb_node)) {
3662                 /*
3663                  * The LSB of head.next can't change to 0 from under
3664                  * us because we hold the mm_all_locks_mutex.
3665                  *
3666                  * We must however clear the bitflag before unlocking
3667                  * the vma so the users using the anon_vma->rb_root will
3668                  * never see our bitflag.
3669                  *
3670                  * No need of atomic instructions here, head.next
3671                  * can't change from under us until we release the
3672                  * anon_vma->root->rwsem.
3673                  */
3674                 if (!__test_and_clear_bit(0, (unsigned long *)
3675                                           &anon_vma->root->rb_root.rb_root.rb_node))
3676                         BUG();
3677                 anon_vma_unlock_write(anon_vma);
3678         }
3679 }
3680
3681 static void vm_unlock_mapping(struct address_space *mapping)
3682 {
3683         if (test_bit(AS_MM_ALL_LOCKS, &mapping->flags)) {
3684                 /*
3685                  * AS_MM_ALL_LOCKS can't change to 0 from under us
3686                  * because we hold the mm_all_locks_mutex.
3687                  */
3688                 i_mmap_unlock_write(mapping);
3689                 if (!test_and_clear_bit(AS_MM_ALL_LOCKS,
3690                                         &mapping->flags))
3691                         BUG();
3692         }
3693 }
3694
3695 /*
3696  * The mmap_lock cannot be released by the caller until
3697  * mm_drop_all_locks() returns.
3698  */
3699 void mm_drop_all_locks(struct mm_struct *mm)
3700 {
3701         struct vm_area_struct *vma;
3702         struct anon_vma_chain *avc;
3703
3704         BUG_ON(mmap_read_trylock(mm));
3705         BUG_ON(!mutex_is_locked(&mm_all_locks_mutex));
3706
3707         for (vma = mm->mmap; vma; vma = vma->vm_next) {
3708                 if (vma->anon_vma)
3709                         list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
3710                                 vm_unlock_anon_vma(avc->anon_vma);
3711                 if (vma->vm_file && vma->vm_file->f_mapping)
3712                         vm_unlock_mapping(vma->vm_file->f_mapping);
3713         }
3714
3715         mutex_unlock(&mm_all_locks_mutex);
3716 }
3717
3718 /*
3719  * initialise the percpu counter for VM
3720  */
3721 void __init mmap_init(void)
3722 {
3723         int ret;
3724
3725         ret = percpu_counter_init(&vm_committed_as, 0, GFP_KERNEL);
3726         VM_BUG_ON(ret);
3727 }
3728
3729 /*
3730  * Initialise sysctl_user_reserve_kbytes.
3731  *
3732  * This is intended to prevent a user from starting a single memory hogging
3733  * process, such that they cannot recover (kill the hog) in OVERCOMMIT_NEVER
3734  * mode.
3735  *
3736  * The default value is min(3% of free memory, 128MB)
3737  * 128MB is enough to recover with sshd/login, bash, and top/kill.
3738  */
3739 static int init_user_reserve(void)
3740 {
3741         unsigned long free_kbytes;
3742
3743         free_kbytes = global_zone_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10);
3744
3745         sysctl_user_reserve_kbytes = min(free_kbytes / 32, 1UL << 17);
3746         return 0;
3747 }
3748 subsys_initcall(init_user_reserve);
3749
3750 /*
3751  * Initialise sysctl_admin_reserve_kbytes.
3752  *
3753  * The purpose of sysctl_admin_reserve_kbytes is to allow the sys admin
3754  * to log in and kill a memory hogging process.
3755  *
3756  * Systems with more than 256MB will reserve 8MB, enough to recover
3757  * with sshd, bash, and top in OVERCOMMIT_GUESS. Smaller systems will
3758  * only reserve 3% of free pages by default.
3759  */
3760 static int init_admin_reserve(void)
3761 {
3762         unsigned long free_kbytes;
3763
3764         free_kbytes = global_zone_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10);
3765
3766         sysctl_admin_reserve_kbytes = min(free_kbytes / 32, 1UL << 13);
3767         return 0;
3768 }
3769 subsys_initcall(init_admin_reserve);
3770
3771 /*
3772  * Reinititalise user and admin reserves if memory is added or removed.
3773  *
3774  * The default user reserve max is 128MB, and the default max for the
3775  * admin reserve is 8MB. These are usually, but not always, enough to
3776  * enable recovery from a memory hogging process using login/sshd, a shell,
3777  * and tools like top. It may make sense to increase or even disable the
3778  * reserve depending on the existence of swap or variations in the recovery
3779  * tools. So, the admin may have changed them.
3780  *
3781  * If memory is added and the reserves have been eliminated or increased above
3782  * the default max, then we'll trust the admin.
3783  *
3784  * If memory is removed and there isn't enough free memory, then we
3785  * need to reset the reserves.
3786  *
3787  * Otherwise keep the reserve set by the admin.
3788  */
3789 static int reserve_mem_notifier(struct notifier_block *nb,
3790                              unsigned long action, void *data)
3791 {
3792         unsigned long tmp, free_kbytes;
3793
3794         switch (action) {
3795         case MEM_ONLINE:
3796                 /* Default max is 128MB. Leave alone if modified by operator. */
3797                 tmp = sysctl_user_reserve_kbytes;
3798                 if (0 < tmp && tmp < (1UL << 17))
3799                         init_user_reserve();
3800
3801                 /* Default max is 8MB.  Leave alone if modified by operator. */
3802                 tmp = sysctl_admin_reserve_kbytes;
3803                 if (0 < tmp && tmp < (1UL << 13))
3804                         init_admin_reserve();
3805
3806                 break;
3807         case MEM_OFFLINE:
3808                 free_kbytes = global_zone_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10);
3809
3810                 if (sysctl_user_reserve_kbytes > free_kbytes) {
3811                         init_user_reserve();
3812                         pr_info("vm.user_reserve_kbytes reset to %lu\n",
3813                                 sysctl_user_reserve_kbytes);
3814                 }
3815
3816                 if (sysctl_admin_reserve_kbytes > free_kbytes) {
3817                         init_admin_reserve();
3818                         pr_info("vm.admin_reserve_kbytes reset to %lu\n",
3819                                 sysctl_admin_reserve_kbytes);
3820                 }
3821                 break;
3822         default:
3823                 break;
3824         }
3825         return NOTIFY_OK;
3826 }
3827
3828 static struct notifier_block reserve_mem_nb = {
3829         .notifier_call = reserve_mem_notifier,
3830 };
3831
3832 static int __meminit init_reserve_notifier(void)
3833 {
3834         if (register_hotmemory_notifier(&reserve_mem_nb))
3835                 pr_err("Failed registering memory add/remove notifier for admin reserve\n");
3836
3837         return 0;
3838 }
3839 subsys_initcall(init_reserve_notifier);