Merge drm/drm-next into drm-intel-next
[platform/kernel/linux-starfive.git] / fs / exec.c
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  *  linux/fs/exec.c
4  *
5  *  Copyright (C) 1991, 1992  Linus Torvalds
6  */
7
8 /*
9  * #!-checking implemented by tytso.
10  */
11 /*
12  * Demand-loading implemented 01.12.91 - no need to read anything but
13  * the header into memory. The inode of the executable is put into
14  * "current->executable", and page faults do the actual loading. Clean.
15  *
16  * Once more I can proudly say that linux stood up to being changed: it
17  * was less than 2 hours work to get demand-loading completely implemented.
18  *
19  * Demand loading changed July 1993 by Eric Youngdale.   Use mmap instead,
20  * current->executable is only used by the procfs.  This allows a dispatch
21  * table to check for several different types  of binary formats.  We keep
22  * trying until we recognize the file or we run out of supported binary
23  * formats.
24  */
25
26 #include <linux/kernel_read_file.h>
27 #include <linux/slab.h>
28 #include <linux/file.h>
29 #include <linux/fdtable.h>
30 #include <linux/mm.h>
31 #include <linux/vmacache.h>
32 #include <linux/stat.h>
33 #include <linux/fcntl.h>
34 #include <linux/swap.h>
35 #include <linux/string.h>
36 #include <linux/init.h>
37 #include <linux/sched/mm.h>
38 #include <linux/sched/coredump.h>
39 #include <linux/sched/signal.h>
40 #include <linux/sched/numa_balancing.h>
41 #include <linux/sched/task.h>
42 #include <linux/pagemap.h>
43 #include <linux/perf_event.h>
44 #include <linux/highmem.h>
45 #include <linux/spinlock.h>
46 #include <linux/key.h>
47 #include <linux/personality.h>
48 #include <linux/binfmts.h>
49 #include <linux/utsname.h>
50 #include <linux/pid_namespace.h>
51 #include <linux/module.h>
52 #include <linux/namei.h>
53 #include <linux/mount.h>
54 #include <linux/security.h>
55 #include <linux/syscalls.h>
56 #include <linux/tsacct_kern.h>
57 #include <linux/cn_proc.h>
58 #include <linux/audit.h>
59 #include <linux/tracehook.h>
60 #include <linux/kmod.h>
61 #include <linux/fsnotify.h>
62 #include <linux/fs_struct.h>
63 #include <linux/oom.h>
64 #include <linux/compat.h>
65 #include <linux/vmalloc.h>
66 #include <linux/io_uring.h>
67 #include <linux/syscall_user_dispatch.h>
68
69 #include <linux/uaccess.h>
70 #include <asm/mmu_context.h>
71 #include <asm/tlb.h>
72
73 #include <trace/events/task.h>
74 #include "internal.h"
75
76 #include <trace/events/sched.h>
77
78 static int bprm_creds_from_file(struct linux_binprm *bprm);
79
80 int suid_dumpable = 0;
81
82 static LIST_HEAD(formats);
83 static DEFINE_RWLOCK(binfmt_lock);
84
85 void __register_binfmt(struct linux_binfmt * fmt, int insert)
86 {
87         BUG_ON(!fmt);
88         if (WARN_ON(!fmt->load_binary))
89                 return;
90         write_lock(&binfmt_lock);
91         insert ? list_add(&fmt->lh, &formats) :
92                  list_add_tail(&fmt->lh, &formats);
93         write_unlock(&binfmt_lock);
94 }
95
96 EXPORT_SYMBOL(__register_binfmt);
97
98 void unregister_binfmt(struct linux_binfmt * fmt)
99 {
100         write_lock(&binfmt_lock);
101         list_del(&fmt->lh);
102         write_unlock(&binfmt_lock);
103 }
104
105 EXPORT_SYMBOL(unregister_binfmt);
106
107 static inline void put_binfmt(struct linux_binfmt * fmt)
108 {
109         module_put(fmt->module);
110 }
111
112 bool path_noexec(const struct path *path)
113 {
114         return (path->mnt->mnt_flags & MNT_NOEXEC) ||
115                (path->mnt->mnt_sb->s_iflags & SB_I_NOEXEC);
116 }
117
118 #ifdef CONFIG_USELIB
119 /*
120  * Note that a shared library must be both readable and executable due to
121  * security reasons.
122  *
123  * Also note that we take the address to load from from the file itself.
124  */
125 SYSCALL_DEFINE1(uselib, const char __user *, library)
126 {
127         struct linux_binfmt *fmt;
128         struct file *file;
129         struct filename *tmp = getname(library);
130         int error = PTR_ERR(tmp);
131         static const struct open_flags uselib_flags = {
132                 .open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC,
133                 .acc_mode = MAY_READ | MAY_EXEC,
134                 .intent = LOOKUP_OPEN,
135                 .lookup_flags = LOOKUP_FOLLOW,
136         };
137
138         if (IS_ERR(tmp))
139                 goto out;
140
141         file = do_filp_open(AT_FDCWD, tmp, &uselib_flags);
142         putname(tmp);
143         error = PTR_ERR(file);
144         if (IS_ERR(file))
145                 goto out;
146
147         /*
148          * may_open() has already checked for this, so it should be
149          * impossible to trip now. But we need to be extra cautious
150          * and check again at the very end too.
151          */
152         error = -EACCES;
153         if (WARN_ON_ONCE(!S_ISREG(file_inode(file)->i_mode) ||
154                          path_noexec(&file->f_path)))
155                 goto exit;
156
157         fsnotify_open(file);
158
159         error = -ENOEXEC;
160
161         read_lock(&binfmt_lock);
162         list_for_each_entry(fmt, &formats, lh) {
163                 if (!fmt->load_shlib)
164                         continue;
165                 if (!try_module_get(fmt->module))
166                         continue;
167                 read_unlock(&binfmt_lock);
168                 error = fmt->load_shlib(file);
169                 read_lock(&binfmt_lock);
170                 put_binfmt(fmt);
171                 if (error != -ENOEXEC)
172                         break;
173         }
174         read_unlock(&binfmt_lock);
175 exit:
176         fput(file);
177 out:
178         return error;
179 }
180 #endif /* #ifdef CONFIG_USELIB */
181
182 #ifdef CONFIG_MMU
183 /*
184  * The nascent bprm->mm is not visible until exec_mmap() but it can
185  * use a lot of memory, account these pages in current->mm temporary
186  * for oom_badness()->get_mm_rss(). Once exec succeeds or fails, we
187  * change the counter back via acct_arg_size(0).
188  */
189 static void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
190 {
191         struct mm_struct *mm = current->mm;
192         long diff = (long)(pages - bprm->vma_pages);
193
194         if (!mm || !diff)
195                 return;
196
197         bprm->vma_pages = pages;
198         add_mm_counter(mm, MM_ANONPAGES, diff);
199 }
200
201 static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
202                 int write)
203 {
204         struct page *page;
205         int ret;
206         unsigned int gup_flags = FOLL_FORCE;
207
208 #ifdef CONFIG_STACK_GROWSUP
209         if (write) {
210                 ret = expand_downwards(bprm->vma, pos);
211                 if (ret < 0)
212                         return NULL;
213         }
214 #endif
215
216         if (write)
217                 gup_flags |= FOLL_WRITE;
218
219         /*
220          * We are doing an exec().  'current' is the process
221          * doing the exec and bprm->mm is the new process's mm.
222          */
223         ret = get_user_pages_remote(bprm->mm, pos, 1, gup_flags,
224                         &page, NULL, NULL);
225         if (ret <= 0)
226                 return NULL;
227
228         if (write)
229                 acct_arg_size(bprm, vma_pages(bprm->vma));
230
231         return page;
232 }
233
234 static void put_arg_page(struct page *page)
235 {
236         put_page(page);
237 }
238
239 static void free_arg_pages(struct linux_binprm *bprm)
240 {
241 }
242
243 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
244                 struct page *page)
245 {
246         flush_cache_page(bprm->vma, pos, page_to_pfn(page));
247 }
248
249 static int __bprm_mm_init(struct linux_binprm *bprm)
250 {
251         int err;
252         struct vm_area_struct *vma = NULL;
253         struct mm_struct *mm = bprm->mm;
254
255         bprm->vma = vma = vm_area_alloc(mm);
256         if (!vma)
257                 return -ENOMEM;
258         vma_set_anonymous(vma);
259
260         if (mmap_write_lock_killable(mm)) {
261                 err = -EINTR;
262                 goto err_free;
263         }
264
265         /*
266          * Place the stack at the largest stack address the architecture
267          * supports. Later, we'll move this to an appropriate place. We don't
268          * use STACK_TOP because that can depend on attributes which aren't
269          * configured yet.
270          */
271         BUILD_BUG_ON(VM_STACK_FLAGS & VM_STACK_INCOMPLETE_SETUP);
272         vma->vm_end = STACK_TOP_MAX;
273         vma->vm_start = vma->vm_end - PAGE_SIZE;
274         vma->vm_flags = VM_SOFTDIRTY | VM_STACK_FLAGS | VM_STACK_INCOMPLETE_SETUP;
275         vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
276
277         err = insert_vm_struct(mm, vma);
278         if (err)
279                 goto err;
280
281         mm->stack_vm = mm->total_vm = 1;
282         mmap_write_unlock(mm);
283         bprm->p = vma->vm_end - sizeof(void *);
284         return 0;
285 err:
286         mmap_write_unlock(mm);
287 err_free:
288         bprm->vma = NULL;
289         vm_area_free(vma);
290         return err;
291 }
292
293 static bool valid_arg_len(struct linux_binprm *bprm, long len)
294 {
295         return len <= MAX_ARG_STRLEN;
296 }
297
298 #else
299
300 static inline void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
301 {
302 }
303
304 static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
305                 int write)
306 {
307         struct page *page;
308
309         page = bprm->page[pos / PAGE_SIZE];
310         if (!page && write) {
311                 page = alloc_page(GFP_HIGHUSER|__GFP_ZERO);
312                 if (!page)
313                         return NULL;
314                 bprm->page[pos / PAGE_SIZE] = page;
315         }
316
317         return page;
318 }
319
320 static void put_arg_page(struct page *page)
321 {
322 }
323
324 static void free_arg_page(struct linux_binprm *bprm, int i)
325 {
326         if (bprm->page[i]) {
327                 __free_page(bprm->page[i]);
328                 bprm->page[i] = NULL;
329         }
330 }
331
332 static void free_arg_pages(struct linux_binprm *bprm)
333 {
334         int i;
335
336         for (i = 0; i < MAX_ARG_PAGES; i++)
337                 free_arg_page(bprm, i);
338 }
339
340 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
341                 struct page *page)
342 {
343 }
344
345 static int __bprm_mm_init(struct linux_binprm *bprm)
346 {
347         bprm->p = PAGE_SIZE * MAX_ARG_PAGES - sizeof(void *);
348         return 0;
349 }
350
351 static bool valid_arg_len(struct linux_binprm *bprm, long len)
352 {
353         return len <= bprm->p;
354 }
355
356 #endif /* CONFIG_MMU */
357
358 /*
359  * Create a new mm_struct and populate it with a temporary stack
360  * vm_area_struct.  We don't have enough context at this point to set the stack
361  * flags, permissions, and offset, so we use temporary values.  We'll update
362  * them later in setup_arg_pages().
363  */
364 static int bprm_mm_init(struct linux_binprm *bprm)
365 {
366         int err;
367         struct mm_struct *mm = NULL;
368
369         bprm->mm = mm = mm_alloc();
370         err = -ENOMEM;
371         if (!mm)
372                 goto err;
373
374         /* Save current stack limit for all calculations made during exec. */
375         task_lock(current->group_leader);
376         bprm->rlim_stack = current->signal->rlim[RLIMIT_STACK];
377         task_unlock(current->group_leader);
378
379         err = __bprm_mm_init(bprm);
380         if (err)
381                 goto err;
382
383         return 0;
384
385 err:
386         if (mm) {
387                 bprm->mm = NULL;
388                 mmdrop(mm);
389         }
390
391         return err;
392 }
393
394 struct user_arg_ptr {
395 #ifdef CONFIG_COMPAT
396         bool is_compat;
397 #endif
398         union {
399                 const char __user *const __user *native;
400 #ifdef CONFIG_COMPAT
401                 const compat_uptr_t __user *compat;
402 #endif
403         } ptr;
404 };
405
406 static const char __user *get_user_arg_ptr(struct user_arg_ptr argv, int nr)
407 {
408         const char __user *native;
409
410 #ifdef CONFIG_COMPAT
411         if (unlikely(argv.is_compat)) {
412                 compat_uptr_t compat;
413
414                 if (get_user(compat, argv.ptr.compat + nr))
415                         return ERR_PTR(-EFAULT);
416
417                 return compat_ptr(compat);
418         }
419 #endif
420
421         if (get_user(native, argv.ptr.native + nr))
422                 return ERR_PTR(-EFAULT);
423
424         return native;
425 }
426
427 /*
428  * count() counts the number of strings in array ARGV.
429  */
430 static int count(struct user_arg_ptr argv, int max)
431 {
432         int i = 0;
433
434         if (argv.ptr.native != NULL) {
435                 for (;;) {
436                         const char __user *p = get_user_arg_ptr(argv, i);
437
438                         if (!p)
439                                 break;
440
441                         if (IS_ERR(p))
442                                 return -EFAULT;
443
444                         if (i >= max)
445                                 return -E2BIG;
446                         ++i;
447
448                         if (fatal_signal_pending(current))
449                                 return -ERESTARTNOHAND;
450                         cond_resched();
451                 }
452         }
453         return i;
454 }
455
456 static int count_strings_kernel(const char *const *argv)
457 {
458         int i;
459
460         if (!argv)
461                 return 0;
462
463         for (i = 0; argv[i]; ++i) {
464                 if (i >= MAX_ARG_STRINGS)
465                         return -E2BIG;
466                 if (fatal_signal_pending(current))
467                         return -ERESTARTNOHAND;
468                 cond_resched();
469         }
470         return i;
471 }
472
473 static int bprm_stack_limits(struct linux_binprm *bprm)
474 {
475         unsigned long limit, ptr_size;
476
477         /*
478          * Limit to 1/4 of the max stack size or 3/4 of _STK_LIM
479          * (whichever is smaller) for the argv+env strings.
480          * This ensures that:
481          *  - the remaining binfmt code will not run out of stack space,
482          *  - the program will have a reasonable amount of stack left
483          *    to work from.
484          */
485         limit = _STK_LIM / 4 * 3;
486         limit = min(limit, bprm->rlim_stack.rlim_cur / 4);
487         /*
488          * We've historically supported up to 32 pages (ARG_MAX)
489          * of argument strings even with small stacks
490          */
491         limit = max_t(unsigned long, limit, ARG_MAX);
492         /*
493          * We must account for the size of all the argv and envp pointers to
494          * the argv and envp strings, since they will also take up space in
495          * the stack. They aren't stored until much later when we can't
496          * signal to the parent that the child has run out of stack space.
497          * Instead, calculate it here so it's possible to fail gracefully.
498          */
499         ptr_size = (bprm->argc + bprm->envc) * sizeof(void *);
500         if (limit <= ptr_size)
501                 return -E2BIG;
502         limit -= ptr_size;
503
504         bprm->argmin = bprm->p - limit;
505         return 0;
506 }
507
508 /*
509  * 'copy_strings()' copies argument/environment strings from the old
510  * processes's memory to the new process's stack.  The call to get_user_pages()
511  * ensures the destination page is created and not swapped out.
512  */
513 static int copy_strings(int argc, struct user_arg_ptr argv,
514                         struct linux_binprm *bprm)
515 {
516         struct page *kmapped_page = NULL;
517         char *kaddr = NULL;
518         unsigned long kpos = 0;
519         int ret;
520
521         while (argc-- > 0) {
522                 const char __user *str;
523                 int len;
524                 unsigned long pos;
525
526                 ret = -EFAULT;
527                 str = get_user_arg_ptr(argv, argc);
528                 if (IS_ERR(str))
529                         goto out;
530
531                 len = strnlen_user(str, MAX_ARG_STRLEN);
532                 if (!len)
533                         goto out;
534
535                 ret = -E2BIG;
536                 if (!valid_arg_len(bprm, len))
537                         goto out;
538
539                 /* We're going to work our way backwords. */
540                 pos = bprm->p;
541                 str += len;
542                 bprm->p -= len;
543 #ifdef CONFIG_MMU
544                 if (bprm->p < bprm->argmin)
545                         goto out;
546 #endif
547
548                 while (len > 0) {
549                         int offset, bytes_to_copy;
550
551                         if (fatal_signal_pending(current)) {
552                                 ret = -ERESTARTNOHAND;
553                                 goto out;
554                         }
555                         cond_resched();
556
557                         offset = pos % PAGE_SIZE;
558                         if (offset == 0)
559                                 offset = PAGE_SIZE;
560
561                         bytes_to_copy = offset;
562                         if (bytes_to_copy > len)
563                                 bytes_to_copy = len;
564
565                         offset -= bytes_to_copy;
566                         pos -= bytes_to_copy;
567                         str -= bytes_to_copy;
568                         len -= bytes_to_copy;
569
570                         if (!kmapped_page || kpos != (pos & PAGE_MASK)) {
571                                 struct page *page;
572
573                                 page = get_arg_page(bprm, pos, 1);
574                                 if (!page) {
575                                         ret = -E2BIG;
576                                         goto out;
577                                 }
578
579                                 if (kmapped_page) {
580                                         flush_kernel_dcache_page(kmapped_page);
581                                         kunmap(kmapped_page);
582                                         put_arg_page(kmapped_page);
583                                 }
584                                 kmapped_page = page;
585                                 kaddr = kmap(kmapped_page);
586                                 kpos = pos & PAGE_MASK;
587                                 flush_arg_page(bprm, kpos, kmapped_page);
588                         }
589                         if (copy_from_user(kaddr+offset, str, bytes_to_copy)) {
590                                 ret = -EFAULT;
591                                 goto out;
592                         }
593                 }
594         }
595         ret = 0;
596 out:
597         if (kmapped_page) {
598                 flush_kernel_dcache_page(kmapped_page);
599                 kunmap(kmapped_page);
600                 put_arg_page(kmapped_page);
601         }
602         return ret;
603 }
604
605 /*
606  * Copy and argument/environment string from the kernel to the processes stack.
607  */
608 int copy_string_kernel(const char *arg, struct linux_binprm *bprm)
609 {
610         int len = strnlen(arg, MAX_ARG_STRLEN) + 1 /* terminating NUL */;
611         unsigned long pos = bprm->p;
612
613         if (len == 0)
614                 return -EFAULT;
615         if (!valid_arg_len(bprm, len))
616                 return -E2BIG;
617
618         /* We're going to work our way backwards. */
619         arg += len;
620         bprm->p -= len;
621         if (IS_ENABLED(CONFIG_MMU) && bprm->p < bprm->argmin)
622                 return -E2BIG;
623
624         while (len > 0) {
625                 unsigned int bytes_to_copy = min_t(unsigned int, len,
626                                 min_not_zero(offset_in_page(pos), PAGE_SIZE));
627                 struct page *page;
628                 char *kaddr;
629
630                 pos -= bytes_to_copy;
631                 arg -= bytes_to_copy;
632                 len -= bytes_to_copy;
633
634                 page = get_arg_page(bprm, pos, 1);
635                 if (!page)
636                         return -E2BIG;
637                 kaddr = kmap_atomic(page);
638                 flush_arg_page(bprm, pos & PAGE_MASK, page);
639                 memcpy(kaddr + offset_in_page(pos), arg, bytes_to_copy);
640                 flush_kernel_dcache_page(page);
641                 kunmap_atomic(kaddr);
642                 put_arg_page(page);
643         }
644
645         return 0;
646 }
647 EXPORT_SYMBOL(copy_string_kernel);
648
649 static int copy_strings_kernel(int argc, const char *const *argv,
650                                struct linux_binprm *bprm)
651 {
652         while (argc-- > 0) {
653                 int ret = copy_string_kernel(argv[argc], bprm);
654                 if (ret < 0)
655                         return ret;
656                 if (fatal_signal_pending(current))
657                         return -ERESTARTNOHAND;
658                 cond_resched();
659         }
660         return 0;
661 }
662
663 #ifdef CONFIG_MMU
664
665 /*
666  * During bprm_mm_init(), we create a temporary stack at STACK_TOP_MAX.  Once
667  * the binfmt code determines where the new stack should reside, we shift it to
668  * its final location.  The process proceeds as follows:
669  *
670  * 1) Use shift to calculate the new vma endpoints.
671  * 2) Extend vma to cover both the old and new ranges.  This ensures the
672  *    arguments passed to subsequent functions are consistent.
673  * 3) Move vma's page tables to the new range.
674  * 4) Free up any cleared pgd range.
675  * 5) Shrink the vma to cover only the new range.
676  */
677 static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift)
678 {
679         struct mm_struct *mm = vma->vm_mm;
680         unsigned long old_start = vma->vm_start;
681         unsigned long old_end = vma->vm_end;
682         unsigned long length = old_end - old_start;
683         unsigned long new_start = old_start - shift;
684         unsigned long new_end = old_end - shift;
685         struct mmu_gather tlb;
686
687         BUG_ON(new_start > new_end);
688
689         /*
690          * ensure there are no vmas between where we want to go
691          * and where we are
692          */
693         if (vma != find_vma(mm, new_start))
694                 return -EFAULT;
695
696         /*
697          * cover the whole range: [new_start, old_end)
698          */
699         if (vma_adjust(vma, new_start, old_end, vma->vm_pgoff, NULL))
700                 return -ENOMEM;
701
702         /*
703          * move the page tables downwards, on failure we rely on
704          * process cleanup to remove whatever mess we made.
705          */
706         if (length != move_page_tables(vma, old_start,
707                                        vma, new_start, length, false))
708                 return -ENOMEM;
709
710         lru_add_drain();
711         tlb_gather_mmu(&tlb, mm);
712         if (new_end > old_start) {
713                 /*
714                  * when the old and new regions overlap clear from new_end.
715                  */
716                 free_pgd_range(&tlb, new_end, old_end, new_end,
717                         vma->vm_next ? vma->vm_next->vm_start : USER_PGTABLES_CEILING);
718         } else {
719                 /*
720                  * otherwise, clean from old_start; this is done to not touch
721                  * the address space in [new_end, old_start) some architectures
722                  * have constraints on va-space that make this illegal (IA64) -
723                  * for the others its just a little faster.
724                  */
725                 free_pgd_range(&tlb, old_start, old_end, new_end,
726                         vma->vm_next ? vma->vm_next->vm_start : USER_PGTABLES_CEILING);
727         }
728         tlb_finish_mmu(&tlb);
729
730         /*
731          * Shrink the vma to just the new range.  Always succeeds.
732          */
733         vma_adjust(vma, new_start, new_end, vma->vm_pgoff, NULL);
734
735         return 0;
736 }
737
738 /*
739  * Finalizes the stack vm_area_struct. The flags and permissions are updated,
740  * the stack is optionally relocated, and some extra space is added.
741  */
742 int setup_arg_pages(struct linux_binprm *bprm,
743                     unsigned long stack_top,
744                     int executable_stack)
745 {
746         unsigned long ret;
747         unsigned long stack_shift;
748         struct mm_struct *mm = current->mm;
749         struct vm_area_struct *vma = bprm->vma;
750         struct vm_area_struct *prev = NULL;
751         unsigned long vm_flags;
752         unsigned long stack_base;
753         unsigned long stack_size;
754         unsigned long stack_expand;
755         unsigned long rlim_stack;
756
757 #ifdef CONFIG_STACK_GROWSUP
758         /* Limit stack size */
759         stack_base = bprm->rlim_stack.rlim_max;
760
761         stack_base = calc_max_stack_size(stack_base);
762
763         /* Add space for stack randomization. */
764         stack_base += (STACK_RND_MASK << PAGE_SHIFT);
765
766         /* Make sure we didn't let the argument array grow too large. */
767         if (vma->vm_end - vma->vm_start > stack_base)
768                 return -ENOMEM;
769
770         stack_base = PAGE_ALIGN(stack_top - stack_base);
771
772         stack_shift = vma->vm_start - stack_base;
773         mm->arg_start = bprm->p - stack_shift;
774         bprm->p = vma->vm_end - stack_shift;
775 #else
776         stack_top = arch_align_stack(stack_top);
777         stack_top = PAGE_ALIGN(stack_top);
778
779         if (unlikely(stack_top < mmap_min_addr) ||
780             unlikely(vma->vm_end - vma->vm_start >= stack_top - mmap_min_addr))
781                 return -ENOMEM;
782
783         stack_shift = vma->vm_end - stack_top;
784
785         bprm->p -= stack_shift;
786         mm->arg_start = bprm->p;
787 #endif
788
789         if (bprm->loader)
790                 bprm->loader -= stack_shift;
791         bprm->exec -= stack_shift;
792
793         if (mmap_write_lock_killable(mm))
794                 return -EINTR;
795
796         vm_flags = VM_STACK_FLAGS;
797
798         /*
799          * Adjust stack execute permissions; explicitly enable for
800          * EXSTACK_ENABLE_X, disable for EXSTACK_DISABLE_X and leave alone
801          * (arch default) otherwise.
802          */
803         if (unlikely(executable_stack == EXSTACK_ENABLE_X))
804                 vm_flags |= VM_EXEC;
805         else if (executable_stack == EXSTACK_DISABLE_X)
806                 vm_flags &= ~VM_EXEC;
807         vm_flags |= mm->def_flags;
808         vm_flags |= VM_STACK_INCOMPLETE_SETUP;
809
810         ret = mprotect_fixup(vma, &prev, vma->vm_start, vma->vm_end,
811                         vm_flags);
812         if (ret)
813                 goto out_unlock;
814         BUG_ON(prev != vma);
815
816         if (unlikely(vm_flags & VM_EXEC)) {
817                 pr_warn_once("process '%pD4' started with executable stack\n",
818                              bprm->file);
819         }
820
821         /* Move stack pages down in memory. */
822         if (stack_shift) {
823                 ret = shift_arg_pages(vma, stack_shift);
824                 if (ret)
825                         goto out_unlock;
826         }
827
828         /* mprotect_fixup is overkill to remove the temporary stack flags */
829         vma->vm_flags &= ~VM_STACK_INCOMPLETE_SETUP;
830
831         stack_expand = 131072UL; /* randomly 32*4k (or 2*64k) pages */
832         stack_size = vma->vm_end - vma->vm_start;
833         /*
834          * Align this down to a page boundary as expand_stack
835          * will align it up.
836          */
837         rlim_stack = bprm->rlim_stack.rlim_cur & PAGE_MASK;
838 #ifdef CONFIG_STACK_GROWSUP
839         if (stack_size + stack_expand > rlim_stack)
840                 stack_base = vma->vm_start + rlim_stack;
841         else
842                 stack_base = vma->vm_end + stack_expand;
843 #else
844         if (stack_size + stack_expand > rlim_stack)
845                 stack_base = vma->vm_end - rlim_stack;
846         else
847                 stack_base = vma->vm_start - stack_expand;
848 #endif
849         current->mm->start_stack = bprm->p;
850         ret = expand_stack(vma, stack_base);
851         if (ret)
852                 ret = -EFAULT;
853
854 out_unlock:
855         mmap_write_unlock(mm);
856         return ret;
857 }
858 EXPORT_SYMBOL(setup_arg_pages);
859
860 #else
861
862 /*
863  * Transfer the program arguments and environment from the holding pages
864  * onto the stack. The provided stack pointer is adjusted accordingly.
865  */
866 int transfer_args_to_stack(struct linux_binprm *bprm,
867                            unsigned long *sp_location)
868 {
869         unsigned long index, stop, sp;
870         int ret = 0;
871
872         stop = bprm->p >> PAGE_SHIFT;
873         sp = *sp_location;
874
875         for (index = MAX_ARG_PAGES - 1; index >= stop; index--) {
876                 unsigned int offset = index == stop ? bprm->p & ~PAGE_MASK : 0;
877                 char *src = kmap(bprm->page[index]) + offset;
878                 sp -= PAGE_SIZE - offset;
879                 if (copy_to_user((void *) sp, src, PAGE_SIZE - offset) != 0)
880                         ret = -EFAULT;
881                 kunmap(bprm->page[index]);
882                 if (ret)
883                         goto out;
884         }
885
886         *sp_location = sp;
887
888 out:
889         return ret;
890 }
891 EXPORT_SYMBOL(transfer_args_to_stack);
892
893 #endif /* CONFIG_MMU */
894
895 static struct file *do_open_execat(int fd, struct filename *name, int flags)
896 {
897         struct file *file;
898         int err;
899         struct open_flags open_exec_flags = {
900                 .open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC,
901                 .acc_mode = MAY_EXEC,
902                 .intent = LOOKUP_OPEN,
903                 .lookup_flags = LOOKUP_FOLLOW,
904         };
905
906         if ((flags & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0)
907                 return ERR_PTR(-EINVAL);
908         if (flags & AT_SYMLINK_NOFOLLOW)
909                 open_exec_flags.lookup_flags &= ~LOOKUP_FOLLOW;
910         if (flags & AT_EMPTY_PATH)
911                 open_exec_flags.lookup_flags |= LOOKUP_EMPTY;
912
913         file = do_filp_open(fd, name, &open_exec_flags);
914         if (IS_ERR(file))
915                 goto out;
916
917         /*
918          * may_open() has already checked for this, so it should be
919          * impossible to trip now. But we need to be extra cautious
920          * and check again at the very end too.
921          */
922         err = -EACCES;
923         if (WARN_ON_ONCE(!S_ISREG(file_inode(file)->i_mode) ||
924                          path_noexec(&file->f_path)))
925                 goto exit;
926
927         err = deny_write_access(file);
928         if (err)
929                 goto exit;
930
931         if (name->name[0] != '\0')
932                 fsnotify_open(file);
933
934 out:
935         return file;
936
937 exit:
938         fput(file);
939         return ERR_PTR(err);
940 }
941
942 struct file *open_exec(const char *name)
943 {
944         struct filename *filename = getname_kernel(name);
945         struct file *f = ERR_CAST(filename);
946
947         if (!IS_ERR(filename)) {
948                 f = do_open_execat(AT_FDCWD, filename, 0);
949                 putname(filename);
950         }
951         return f;
952 }
953 EXPORT_SYMBOL(open_exec);
954
955 #if defined(CONFIG_HAVE_AOUT) || defined(CONFIG_BINFMT_FLAT) || \
956     defined(CONFIG_BINFMT_ELF_FDPIC)
957 ssize_t read_code(struct file *file, unsigned long addr, loff_t pos, size_t len)
958 {
959         ssize_t res = vfs_read(file, (void __user *)addr, len, &pos);
960         if (res > 0)
961                 flush_icache_user_range(addr, addr + len);
962         return res;
963 }
964 EXPORT_SYMBOL(read_code);
965 #endif
966
967 /*
968  * Maps the mm_struct mm into the current task struct.
969  * On success, this function returns with exec_update_lock
970  * held for writing.
971  */
972 static int exec_mmap(struct mm_struct *mm)
973 {
974         struct task_struct *tsk;
975         struct mm_struct *old_mm, *active_mm;
976         int ret;
977
978         /* Notify parent that we're no longer interested in the old VM */
979         tsk = current;
980         old_mm = current->mm;
981         exec_mm_release(tsk, old_mm);
982         if (old_mm)
983                 sync_mm_rss(old_mm);
984
985         ret = down_write_killable(&tsk->signal->exec_update_lock);
986         if (ret)
987                 return ret;
988
989         if (old_mm) {
990                 /*
991                  * Make sure that if there is a core dump in progress
992                  * for the old mm, we get out and die instead of going
993                  * through with the exec.  We must hold mmap_lock around
994                  * checking core_state and changing tsk->mm.
995                  */
996                 mmap_read_lock(old_mm);
997                 if (unlikely(old_mm->core_state)) {
998                         mmap_read_unlock(old_mm);
999                         up_write(&tsk->signal->exec_update_lock);
1000                         return -EINTR;
1001                 }
1002         }
1003
1004         task_lock(tsk);
1005         membarrier_exec_mmap(mm);
1006
1007         local_irq_disable();
1008         active_mm = tsk->active_mm;
1009         tsk->active_mm = mm;
1010         tsk->mm = mm;
1011         /*
1012          * This prevents preemption while active_mm is being loaded and
1013          * it and mm are being updated, which could cause problems for
1014          * lazy tlb mm refcounting when these are updated by context
1015          * switches. Not all architectures can handle irqs off over
1016          * activate_mm yet.
1017          */
1018         if (!IS_ENABLED(CONFIG_ARCH_WANT_IRQS_OFF_ACTIVATE_MM))
1019                 local_irq_enable();
1020         activate_mm(active_mm, mm);
1021         if (IS_ENABLED(CONFIG_ARCH_WANT_IRQS_OFF_ACTIVATE_MM))
1022                 local_irq_enable();
1023         tsk->mm->vmacache_seqnum = 0;
1024         vmacache_flush(tsk);
1025         task_unlock(tsk);
1026         if (old_mm) {
1027                 mmap_read_unlock(old_mm);
1028                 BUG_ON(active_mm != old_mm);
1029                 setmax_mm_hiwater_rss(&tsk->signal->maxrss, old_mm);
1030                 mm_update_next_owner(old_mm);
1031                 mmput(old_mm);
1032                 return 0;
1033         }
1034         mmdrop(active_mm);
1035         return 0;
1036 }
1037
1038 static int de_thread(struct task_struct *tsk)
1039 {
1040         struct signal_struct *sig = tsk->signal;
1041         struct sighand_struct *oldsighand = tsk->sighand;
1042         spinlock_t *lock = &oldsighand->siglock;
1043
1044         if (thread_group_empty(tsk))
1045                 goto no_thread_group;
1046
1047         /*
1048          * Kill all other threads in the thread group.
1049          */
1050         spin_lock_irq(lock);
1051         if (signal_group_exit(sig)) {
1052                 /*
1053                  * Another group action in progress, just
1054                  * return so that the signal is processed.
1055                  */
1056                 spin_unlock_irq(lock);
1057                 return -EAGAIN;
1058         }
1059
1060         sig->group_exit_task = tsk;
1061         sig->notify_count = zap_other_threads(tsk);
1062         if (!thread_group_leader(tsk))
1063                 sig->notify_count--;
1064
1065         while (sig->notify_count) {
1066                 __set_current_state(TASK_KILLABLE);
1067                 spin_unlock_irq(lock);
1068                 schedule();
1069                 if (__fatal_signal_pending(tsk))
1070                         goto killed;
1071                 spin_lock_irq(lock);
1072         }
1073         spin_unlock_irq(lock);
1074
1075         /*
1076          * At this point all other threads have exited, all we have to
1077          * do is to wait for the thread group leader to become inactive,
1078          * and to assume its PID:
1079          */
1080         if (!thread_group_leader(tsk)) {
1081                 struct task_struct *leader = tsk->group_leader;
1082
1083                 for (;;) {
1084                         cgroup_threadgroup_change_begin(tsk);
1085                         write_lock_irq(&tasklist_lock);
1086                         /*
1087                          * Do this under tasklist_lock to ensure that
1088                          * exit_notify() can't miss ->group_exit_task
1089                          */
1090                         sig->notify_count = -1;
1091                         if (likely(leader->exit_state))
1092                                 break;
1093                         __set_current_state(TASK_KILLABLE);
1094                         write_unlock_irq(&tasklist_lock);
1095                         cgroup_threadgroup_change_end(tsk);
1096                         schedule();
1097                         if (__fatal_signal_pending(tsk))
1098                                 goto killed;
1099                 }
1100
1101                 /*
1102                  * The only record we have of the real-time age of a
1103                  * process, regardless of execs it's done, is start_time.
1104                  * All the past CPU time is accumulated in signal_struct
1105                  * from sister threads now dead.  But in this non-leader
1106                  * exec, nothing survives from the original leader thread,
1107                  * whose birth marks the true age of this process now.
1108                  * When we take on its identity by switching to its PID, we
1109                  * also take its birthdate (always earlier than our own).
1110                  */
1111                 tsk->start_time = leader->start_time;
1112                 tsk->start_boottime = leader->start_boottime;
1113
1114                 BUG_ON(!same_thread_group(leader, tsk));
1115                 /*
1116                  * An exec() starts a new thread group with the
1117                  * TGID of the previous thread group. Rehash the
1118                  * two threads with a switched PID, and release
1119                  * the former thread group leader:
1120                  */
1121
1122                 /* Become a process group leader with the old leader's pid.
1123                  * The old leader becomes a thread of the this thread group.
1124                  */
1125                 exchange_tids(tsk, leader);
1126                 transfer_pid(leader, tsk, PIDTYPE_TGID);
1127                 transfer_pid(leader, tsk, PIDTYPE_PGID);
1128                 transfer_pid(leader, tsk, PIDTYPE_SID);
1129
1130                 list_replace_rcu(&leader->tasks, &tsk->tasks);
1131                 list_replace_init(&leader->sibling, &tsk->sibling);
1132
1133                 tsk->group_leader = tsk;
1134                 leader->group_leader = tsk;
1135
1136                 tsk->exit_signal = SIGCHLD;
1137                 leader->exit_signal = -1;
1138
1139                 BUG_ON(leader->exit_state != EXIT_ZOMBIE);
1140                 leader->exit_state = EXIT_DEAD;
1141
1142                 /*
1143                  * We are going to release_task()->ptrace_unlink() silently,
1144                  * the tracer can sleep in do_wait(). EXIT_DEAD guarantees
1145                  * the tracer wont't block again waiting for this thread.
1146                  */
1147                 if (unlikely(leader->ptrace))
1148                         __wake_up_parent(leader, leader->parent);
1149                 write_unlock_irq(&tasklist_lock);
1150                 cgroup_threadgroup_change_end(tsk);
1151
1152                 release_task(leader);
1153         }
1154
1155         sig->group_exit_task = NULL;
1156         sig->notify_count = 0;
1157
1158 no_thread_group:
1159         /* we have changed execution domain */
1160         tsk->exit_signal = SIGCHLD;
1161
1162         BUG_ON(!thread_group_leader(tsk));
1163         return 0;
1164
1165 killed:
1166         /* protects against exit_notify() and __exit_signal() */
1167         read_lock(&tasklist_lock);
1168         sig->group_exit_task = NULL;
1169         sig->notify_count = 0;
1170         read_unlock(&tasklist_lock);
1171         return -EAGAIN;
1172 }
1173
1174
1175 /*
1176  * This function makes sure the current process has its own signal table,
1177  * so that flush_signal_handlers can later reset the handlers without
1178  * disturbing other processes.  (Other processes might share the signal
1179  * table via the CLONE_SIGHAND option to clone().)
1180  */
1181 static int unshare_sighand(struct task_struct *me)
1182 {
1183         struct sighand_struct *oldsighand = me->sighand;
1184
1185         if (refcount_read(&oldsighand->count) != 1) {
1186                 struct sighand_struct *newsighand;
1187                 /*
1188                  * This ->sighand is shared with the CLONE_SIGHAND
1189                  * but not CLONE_THREAD task, switch to the new one.
1190                  */
1191                 newsighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1192                 if (!newsighand)
1193                         return -ENOMEM;
1194
1195                 refcount_set(&newsighand->count, 1);
1196                 memcpy(newsighand->action, oldsighand->action,
1197                        sizeof(newsighand->action));
1198
1199                 write_lock_irq(&tasklist_lock);
1200                 spin_lock(&oldsighand->siglock);
1201                 rcu_assign_pointer(me->sighand, newsighand);
1202                 spin_unlock(&oldsighand->siglock);
1203                 write_unlock_irq(&tasklist_lock);
1204
1205                 __cleanup_sighand(oldsighand);
1206         }
1207         return 0;
1208 }
1209
1210 char *__get_task_comm(char *buf, size_t buf_size, struct task_struct *tsk)
1211 {
1212         task_lock(tsk);
1213         strncpy(buf, tsk->comm, buf_size);
1214         task_unlock(tsk);
1215         return buf;
1216 }
1217 EXPORT_SYMBOL_GPL(__get_task_comm);
1218
1219 /*
1220  * These functions flushes out all traces of the currently running executable
1221  * so that a new one can be started
1222  */
1223
1224 void __set_task_comm(struct task_struct *tsk, const char *buf, bool exec)
1225 {
1226         task_lock(tsk);
1227         trace_task_rename(tsk, buf);
1228         strlcpy(tsk->comm, buf, sizeof(tsk->comm));
1229         task_unlock(tsk);
1230         perf_event_comm(tsk, exec);
1231 }
1232
1233 /*
1234  * Calling this is the point of no return. None of the failures will be
1235  * seen by userspace since either the process is already taking a fatal
1236  * signal (via de_thread() or coredump), or will have SEGV raised
1237  * (after exec_mmap()) by search_binary_handler (see below).
1238  */
1239 int begin_new_exec(struct linux_binprm * bprm)
1240 {
1241         struct task_struct *me = current;
1242         int retval;
1243
1244         /* Once we are committed compute the creds */
1245         retval = bprm_creds_from_file(bprm);
1246         if (retval)
1247                 return retval;
1248
1249         /*
1250          * Ensure all future errors are fatal.
1251          */
1252         bprm->point_of_no_return = true;
1253
1254         /*
1255          * Make this the only thread in the thread group.
1256          */
1257         retval = de_thread(me);
1258         if (retval)
1259                 goto out;
1260
1261         /*
1262          * Cancel any io_uring activity across execve
1263          */
1264         io_uring_task_cancel();
1265
1266         /* Ensure the files table is not shared. */
1267         retval = unshare_files();
1268         if (retval)
1269                 goto out;
1270
1271         /*
1272          * Must be called _before_ exec_mmap() as bprm->mm is
1273          * not visibile until then. This also enables the update
1274          * to be lockless.
1275          */
1276         set_mm_exe_file(bprm->mm, bprm->file);
1277
1278         /* If the binary is not readable then enforce mm->dumpable=0 */
1279         would_dump(bprm, bprm->file);
1280         if (bprm->have_execfd)
1281                 would_dump(bprm, bprm->executable);
1282
1283         /*
1284          * Release all of the old mmap stuff
1285          */
1286         acct_arg_size(bprm, 0);
1287         retval = exec_mmap(bprm->mm);
1288         if (retval)
1289                 goto out;
1290
1291         bprm->mm = NULL;
1292
1293 #ifdef CONFIG_POSIX_TIMERS
1294         exit_itimers(me->signal);
1295         flush_itimer_signals();
1296 #endif
1297
1298         /*
1299          * Make the signal table private.
1300          */
1301         retval = unshare_sighand(me);
1302         if (retval)
1303                 goto out_unlock;
1304
1305         /*
1306          * Ensure that the uaccess routines can actually operate on userspace
1307          * pointers:
1308          */
1309         force_uaccess_begin();
1310
1311         me->flags &= ~(PF_RANDOMIZE | PF_FORKNOEXEC | PF_KTHREAD |
1312                                         PF_NOFREEZE | PF_NO_SETAFFINITY);
1313         flush_thread();
1314         me->personality &= ~bprm->per_clear;
1315
1316         clear_syscall_work_syscall_user_dispatch(me);
1317
1318         /*
1319          * We have to apply CLOEXEC before we change whether the process is
1320          * dumpable (in setup_new_exec) to avoid a race with a process in userspace
1321          * trying to access the should-be-closed file descriptors of a process
1322          * undergoing exec(2).
1323          */
1324         do_close_on_exec(me->files);
1325
1326         if (bprm->secureexec) {
1327                 /* Make sure parent cannot signal privileged process. */
1328                 me->pdeath_signal = 0;
1329
1330                 /*
1331                  * For secureexec, reset the stack limit to sane default to
1332                  * avoid bad behavior from the prior rlimits. This has to
1333                  * happen before arch_pick_mmap_layout(), which examines
1334                  * RLIMIT_STACK, but after the point of no return to avoid
1335                  * needing to clean up the change on failure.
1336                  */
1337                 if (bprm->rlim_stack.rlim_cur > _STK_LIM)
1338                         bprm->rlim_stack.rlim_cur = _STK_LIM;
1339         }
1340
1341         me->sas_ss_sp = me->sas_ss_size = 0;
1342
1343         /*
1344          * Figure out dumpability. Note that this checking only of current
1345          * is wrong, but userspace depends on it. This should be testing
1346          * bprm->secureexec instead.
1347          */
1348         if (bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP ||
1349             !(uid_eq(current_euid(), current_uid()) &&
1350               gid_eq(current_egid(), current_gid())))
1351                 set_dumpable(current->mm, suid_dumpable);
1352         else
1353                 set_dumpable(current->mm, SUID_DUMP_USER);
1354
1355         perf_event_exec();
1356         __set_task_comm(me, kbasename(bprm->filename), true);
1357
1358         /* An exec changes our domain. We are no longer part of the thread
1359            group */
1360         WRITE_ONCE(me->self_exec_id, me->self_exec_id + 1);
1361         flush_signal_handlers(me, 0);
1362
1363         /*
1364          * install the new credentials for this executable
1365          */
1366         security_bprm_committing_creds(bprm);
1367
1368         commit_creds(bprm->cred);
1369         bprm->cred = NULL;
1370
1371         /*
1372          * Disable monitoring for regular users
1373          * when executing setuid binaries. Must
1374          * wait until new credentials are committed
1375          * by commit_creds() above
1376          */
1377         if (get_dumpable(me->mm) != SUID_DUMP_USER)
1378                 perf_event_exit_task(me);
1379         /*
1380          * cred_guard_mutex must be held at least to this point to prevent
1381          * ptrace_attach() from altering our determination of the task's
1382          * credentials; any time after this it may be unlocked.
1383          */
1384         security_bprm_committed_creds(bprm);
1385
1386         /* Pass the opened binary to the interpreter. */
1387         if (bprm->have_execfd) {
1388                 retval = get_unused_fd_flags(0);
1389                 if (retval < 0)
1390                         goto out_unlock;
1391                 fd_install(retval, bprm->executable);
1392                 bprm->executable = NULL;
1393                 bprm->execfd = retval;
1394         }
1395         return 0;
1396
1397 out_unlock:
1398         up_write(&me->signal->exec_update_lock);
1399 out:
1400         return retval;
1401 }
1402 EXPORT_SYMBOL(begin_new_exec);
1403
1404 void would_dump(struct linux_binprm *bprm, struct file *file)
1405 {
1406         struct inode *inode = file_inode(file);
1407         struct user_namespace *mnt_userns = file_mnt_user_ns(file);
1408         if (inode_permission(mnt_userns, inode, MAY_READ) < 0) {
1409                 struct user_namespace *old, *user_ns;
1410                 bprm->interp_flags |= BINPRM_FLAGS_ENFORCE_NONDUMP;
1411
1412                 /* Ensure mm->user_ns contains the executable */
1413                 user_ns = old = bprm->mm->user_ns;
1414                 while ((user_ns != &init_user_ns) &&
1415                        !privileged_wrt_inode_uidgid(user_ns, mnt_userns, inode))
1416                         user_ns = user_ns->parent;
1417
1418                 if (old != user_ns) {
1419                         bprm->mm->user_ns = get_user_ns(user_ns);
1420                         put_user_ns(old);
1421                 }
1422         }
1423 }
1424 EXPORT_SYMBOL(would_dump);
1425
1426 void setup_new_exec(struct linux_binprm * bprm)
1427 {
1428         /* Setup things that can depend upon the personality */
1429         struct task_struct *me = current;
1430
1431         arch_pick_mmap_layout(me->mm, &bprm->rlim_stack);
1432
1433         arch_setup_new_exec();
1434
1435         /* Set the new mm task size. We have to do that late because it may
1436          * depend on TIF_32BIT which is only updated in flush_thread() on
1437          * some architectures like powerpc
1438          */
1439         me->mm->task_size = TASK_SIZE;
1440         up_write(&me->signal->exec_update_lock);
1441         mutex_unlock(&me->signal->cred_guard_mutex);
1442 }
1443 EXPORT_SYMBOL(setup_new_exec);
1444
1445 /* Runs immediately before start_thread() takes over. */
1446 void finalize_exec(struct linux_binprm *bprm)
1447 {
1448         /* Store any stack rlimit changes before starting thread. */
1449         task_lock(current->group_leader);
1450         current->signal->rlim[RLIMIT_STACK] = bprm->rlim_stack;
1451         task_unlock(current->group_leader);
1452 }
1453 EXPORT_SYMBOL(finalize_exec);
1454
1455 /*
1456  * Prepare credentials and lock ->cred_guard_mutex.
1457  * setup_new_exec() commits the new creds and drops the lock.
1458  * Or, if exec fails before, free_bprm() should release ->cred
1459  * and unlock.
1460  */
1461 static int prepare_bprm_creds(struct linux_binprm *bprm)
1462 {
1463         if (mutex_lock_interruptible(&current->signal->cred_guard_mutex))
1464                 return -ERESTARTNOINTR;
1465
1466         bprm->cred = prepare_exec_creds();
1467         if (likely(bprm->cred))
1468                 return 0;
1469
1470         mutex_unlock(&current->signal->cred_guard_mutex);
1471         return -ENOMEM;
1472 }
1473
1474 static void free_bprm(struct linux_binprm *bprm)
1475 {
1476         if (bprm->mm) {
1477                 acct_arg_size(bprm, 0);
1478                 mmput(bprm->mm);
1479         }
1480         free_arg_pages(bprm);
1481         if (bprm->cred) {
1482                 mutex_unlock(&current->signal->cred_guard_mutex);
1483                 abort_creds(bprm->cred);
1484         }
1485         if (bprm->file) {
1486                 allow_write_access(bprm->file);
1487                 fput(bprm->file);
1488         }
1489         if (bprm->executable)
1490                 fput(bprm->executable);
1491         /* If a binfmt changed the interp, free it. */
1492         if (bprm->interp != bprm->filename)
1493                 kfree(bprm->interp);
1494         kfree(bprm->fdpath);
1495         kfree(bprm);
1496 }
1497
1498 static struct linux_binprm *alloc_bprm(int fd, struct filename *filename)
1499 {
1500         struct linux_binprm *bprm = kzalloc(sizeof(*bprm), GFP_KERNEL);
1501         int retval = -ENOMEM;
1502         if (!bprm)
1503                 goto out;
1504
1505         if (fd == AT_FDCWD || filename->name[0] == '/') {
1506                 bprm->filename = filename->name;
1507         } else {
1508                 if (filename->name[0] == '\0')
1509                         bprm->fdpath = kasprintf(GFP_KERNEL, "/dev/fd/%d", fd);
1510                 else
1511                         bprm->fdpath = kasprintf(GFP_KERNEL, "/dev/fd/%d/%s",
1512                                                   fd, filename->name);
1513                 if (!bprm->fdpath)
1514                         goto out_free;
1515
1516                 bprm->filename = bprm->fdpath;
1517         }
1518         bprm->interp = bprm->filename;
1519
1520         retval = bprm_mm_init(bprm);
1521         if (retval)
1522                 goto out_free;
1523         return bprm;
1524
1525 out_free:
1526         free_bprm(bprm);
1527 out:
1528         return ERR_PTR(retval);
1529 }
1530
1531 int bprm_change_interp(const char *interp, struct linux_binprm *bprm)
1532 {
1533         /* If a binfmt changed the interp, free it first. */
1534         if (bprm->interp != bprm->filename)
1535                 kfree(bprm->interp);
1536         bprm->interp = kstrdup(interp, GFP_KERNEL);
1537         if (!bprm->interp)
1538                 return -ENOMEM;
1539         return 0;
1540 }
1541 EXPORT_SYMBOL(bprm_change_interp);
1542
1543 /*
1544  * determine how safe it is to execute the proposed program
1545  * - the caller must hold ->cred_guard_mutex to protect against
1546  *   PTRACE_ATTACH or seccomp thread-sync
1547  */
1548 static void check_unsafe_exec(struct linux_binprm *bprm)
1549 {
1550         struct task_struct *p = current, *t;
1551         unsigned n_fs;
1552
1553         if (p->ptrace)
1554                 bprm->unsafe |= LSM_UNSAFE_PTRACE;
1555
1556         /*
1557          * This isn't strictly necessary, but it makes it harder for LSMs to
1558          * mess up.
1559          */
1560         if (task_no_new_privs(current))
1561                 bprm->unsafe |= LSM_UNSAFE_NO_NEW_PRIVS;
1562
1563         t = p;
1564         n_fs = 1;
1565         spin_lock(&p->fs->lock);
1566         rcu_read_lock();
1567         while_each_thread(p, t) {
1568                 if (t->fs == p->fs)
1569                         n_fs++;
1570         }
1571         rcu_read_unlock();
1572
1573         if (p->fs->users > n_fs)
1574                 bprm->unsafe |= LSM_UNSAFE_SHARE;
1575         else
1576                 p->fs->in_exec = 1;
1577         spin_unlock(&p->fs->lock);
1578 }
1579
1580 static void bprm_fill_uid(struct linux_binprm *bprm, struct file *file)
1581 {
1582         /* Handle suid and sgid on files */
1583         struct user_namespace *mnt_userns;
1584         struct inode *inode;
1585         unsigned int mode;
1586         kuid_t uid;
1587         kgid_t gid;
1588
1589         if (!mnt_may_suid(file->f_path.mnt))
1590                 return;
1591
1592         if (task_no_new_privs(current))
1593                 return;
1594
1595         inode = file->f_path.dentry->d_inode;
1596         mode = READ_ONCE(inode->i_mode);
1597         if (!(mode & (S_ISUID|S_ISGID)))
1598                 return;
1599
1600         mnt_userns = file_mnt_user_ns(file);
1601
1602         /* Be careful if suid/sgid is set */
1603         inode_lock(inode);
1604
1605         /* reload atomically mode/uid/gid now that lock held */
1606         mode = inode->i_mode;
1607         uid = i_uid_into_mnt(mnt_userns, inode);
1608         gid = i_gid_into_mnt(mnt_userns, inode);
1609         inode_unlock(inode);
1610
1611         /* We ignore suid/sgid if there are no mappings for them in the ns */
1612         if (!kuid_has_mapping(bprm->cred->user_ns, uid) ||
1613                  !kgid_has_mapping(bprm->cred->user_ns, gid))
1614                 return;
1615
1616         if (mode & S_ISUID) {
1617                 bprm->per_clear |= PER_CLEAR_ON_SETID;
1618                 bprm->cred->euid = uid;
1619         }
1620
1621         if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
1622                 bprm->per_clear |= PER_CLEAR_ON_SETID;
1623                 bprm->cred->egid = gid;
1624         }
1625 }
1626
1627 /*
1628  * Compute brpm->cred based upon the final binary.
1629  */
1630 static int bprm_creds_from_file(struct linux_binprm *bprm)
1631 {
1632         /* Compute creds based on which file? */
1633         struct file *file = bprm->execfd_creds ? bprm->executable : bprm->file;
1634
1635         bprm_fill_uid(bprm, file);
1636         return security_bprm_creds_from_file(bprm, file);
1637 }
1638
1639 /*
1640  * Fill the binprm structure from the inode.
1641  * Read the first BINPRM_BUF_SIZE bytes
1642  *
1643  * This may be called multiple times for binary chains (scripts for example).
1644  */
1645 static int prepare_binprm(struct linux_binprm *bprm)
1646 {
1647         loff_t pos = 0;
1648
1649         memset(bprm->buf, 0, BINPRM_BUF_SIZE);
1650         return kernel_read(bprm->file, bprm->buf, BINPRM_BUF_SIZE, &pos);
1651 }
1652
1653 /*
1654  * Arguments are '\0' separated strings found at the location bprm->p
1655  * points to; chop off the first by relocating brpm->p to right after
1656  * the first '\0' encountered.
1657  */
1658 int remove_arg_zero(struct linux_binprm *bprm)
1659 {
1660         int ret = 0;
1661         unsigned long offset;
1662         char *kaddr;
1663         struct page *page;
1664
1665         if (!bprm->argc)
1666                 return 0;
1667
1668         do {
1669                 offset = bprm->p & ~PAGE_MASK;
1670                 page = get_arg_page(bprm, bprm->p, 0);
1671                 if (!page) {
1672                         ret = -EFAULT;
1673                         goto out;
1674                 }
1675                 kaddr = kmap_atomic(page);
1676
1677                 for (; offset < PAGE_SIZE && kaddr[offset];
1678                                 offset++, bprm->p++)
1679                         ;
1680
1681                 kunmap_atomic(kaddr);
1682                 put_arg_page(page);
1683         } while (offset == PAGE_SIZE);
1684
1685         bprm->p++;
1686         bprm->argc--;
1687         ret = 0;
1688
1689 out:
1690         return ret;
1691 }
1692 EXPORT_SYMBOL(remove_arg_zero);
1693
1694 #define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e))
1695 /*
1696  * cycle the list of binary formats handler, until one recognizes the image
1697  */
1698 static int search_binary_handler(struct linux_binprm *bprm)
1699 {
1700         bool need_retry = IS_ENABLED(CONFIG_MODULES);
1701         struct linux_binfmt *fmt;
1702         int retval;
1703
1704         retval = prepare_binprm(bprm);
1705         if (retval < 0)
1706                 return retval;
1707
1708         retval = security_bprm_check(bprm);
1709         if (retval)
1710                 return retval;
1711
1712         retval = -ENOENT;
1713  retry:
1714         read_lock(&binfmt_lock);
1715         list_for_each_entry(fmt, &formats, lh) {
1716                 if (!try_module_get(fmt->module))
1717                         continue;
1718                 read_unlock(&binfmt_lock);
1719
1720                 retval = fmt->load_binary(bprm);
1721
1722                 read_lock(&binfmt_lock);
1723                 put_binfmt(fmt);
1724                 if (bprm->point_of_no_return || (retval != -ENOEXEC)) {
1725                         read_unlock(&binfmt_lock);
1726                         return retval;
1727                 }
1728         }
1729         read_unlock(&binfmt_lock);
1730
1731         if (need_retry) {
1732                 if (printable(bprm->buf[0]) && printable(bprm->buf[1]) &&
1733                     printable(bprm->buf[2]) && printable(bprm->buf[3]))
1734                         return retval;
1735                 if (request_module("binfmt-%04x", *(ushort *)(bprm->buf + 2)) < 0)
1736                         return retval;
1737                 need_retry = false;
1738                 goto retry;
1739         }
1740
1741         return retval;
1742 }
1743
1744 static int exec_binprm(struct linux_binprm *bprm)
1745 {
1746         pid_t old_pid, old_vpid;
1747         int ret, depth;
1748
1749         /* Need to fetch pid before load_binary changes it */
1750         old_pid = current->pid;
1751         rcu_read_lock();
1752         old_vpid = task_pid_nr_ns(current, task_active_pid_ns(current->parent));
1753         rcu_read_unlock();
1754
1755         /* This allows 4 levels of binfmt rewrites before failing hard. */
1756         for (depth = 0;; depth++) {
1757                 struct file *exec;
1758                 if (depth > 5)
1759                         return -ELOOP;
1760
1761                 ret = search_binary_handler(bprm);
1762                 if (ret < 0)
1763                         return ret;
1764                 if (!bprm->interpreter)
1765                         break;
1766
1767                 exec = bprm->file;
1768                 bprm->file = bprm->interpreter;
1769                 bprm->interpreter = NULL;
1770
1771                 allow_write_access(exec);
1772                 if (unlikely(bprm->have_execfd)) {
1773                         if (bprm->executable) {
1774                                 fput(exec);
1775                                 return -ENOEXEC;
1776                         }
1777                         bprm->executable = exec;
1778                 } else
1779                         fput(exec);
1780         }
1781
1782         audit_bprm(bprm);
1783         trace_sched_process_exec(current, old_pid, bprm);
1784         ptrace_event(PTRACE_EVENT_EXEC, old_vpid);
1785         proc_exec_connector(current);
1786         return 0;
1787 }
1788
1789 /*
1790  * sys_execve() executes a new program.
1791  */
1792 static int bprm_execve(struct linux_binprm *bprm,
1793                        int fd, struct filename *filename, int flags)
1794 {
1795         struct file *file;
1796         int retval;
1797
1798         retval = prepare_bprm_creds(bprm);
1799         if (retval)
1800                 return retval;
1801
1802         check_unsafe_exec(bprm);
1803         current->in_execve = 1;
1804
1805         file = do_open_execat(fd, filename, flags);
1806         retval = PTR_ERR(file);
1807         if (IS_ERR(file))
1808                 goto out_unmark;
1809
1810         sched_exec();
1811
1812         bprm->file = file;
1813         /*
1814          * Record that a name derived from an O_CLOEXEC fd will be
1815          * inaccessible after exec.  This allows the code in exec to
1816          * choose to fail when the executable is not mmaped into the
1817          * interpreter and an open file descriptor is not passed to
1818          * the interpreter.  This makes for a better user experience
1819          * than having the interpreter start and then immediately fail
1820          * when it finds the executable is inaccessible.
1821          */
1822         if (bprm->fdpath && get_close_on_exec(fd))
1823                 bprm->interp_flags |= BINPRM_FLAGS_PATH_INACCESSIBLE;
1824
1825         /* Set the unchanging part of bprm->cred */
1826         retval = security_bprm_creds_for_exec(bprm);
1827         if (retval)
1828                 goto out;
1829
1830         retval = exec_binprm(bprm);
1831         if (retval < 0)
1832                 goto out;
1833
1834         /* execve succeeded */
1835         current->fs->in_exec = 0;
1836         current->in_execve = 0;
1837         rseq_execve(current);
1838         acct_update_integrals(current);
1839         task_numa_free(current, false);
1840         return retval;
1841
1842 out:
1843         /*
1844          * If past the point of no return ensure the code never
1845          * returns to the userspace process.  Use an existing fatal
1846          * signal if present otherwise terminate the process with
1847          * SIGSEGV.
1848          */
1849         if (bprm->point_of_no_return && !fatal_signal_pending(current))
1850                 force_sigsegv(SIGSEGV);
1851
1852 out_unmark:
1853         current->fs->in_exec = 0;
1854         current->in_execve = 0;
1855
1856         return retval;
1857 }
1858
1859 static int do_execveat_common(int fd, struct filename *filename,
1860                               struct user_arg_ptr argv,
1861                               struct user_arg_ptr envp,
1862                               int flags)
1863 {
1864         struct linux_binprm *bprm;
1865         int retval;
1866
1867         if (IS_ERR(filename))
1868                 return PTR_ERR(filename);
1869
1870         /*
1871          * We move the actual failure in case of RLIMIT_NPROC excess from
1872          * set*uid() to execve() because too many poorly written programs
1873          * don't check setuid() return code.  Here we additionally recheck
1874          * whether NPROC limit is still exceeded.
1875          */
1876         if ((current->flags & PF_NPROC_EXCEEDED) &&
1877             atomic_read(&current_user()->processes) > rlimit(RLIMIT_NPROC)) {
1878                 retval = -EAGAIN;
1879                 goto out_ret;
1880         }
1881
1882         /* We're below the limit (still or again), so we don't want to make
1883          * further execve() calls fail. */
1884         current->flags &= ~PF_NPROC_EXCEEDED;
1885
1886         bprm = alloc_bprm(fd, filename);
1887         if (IS_ERR(bprm)) {
1888                 retval = PTR_ERR(bprm);
1889                 goto out_ret;
1890         }
1891
1892         retval = count(argv, MAX_ARG_STRINGS);
1893         if (retval < 0)
1894                 goto out_free;
1895         bprm->argc = retval;
1896
1897         retval = count(envp, MAX_ARG_STRINGS);
1898         if (retval < 0)
1899                 goto out_free;
1900         bprm->envc = retval;
1901
1902         retval = bprm_stack_limits(bprm);
1903         if (retval < 0)
1904                 goto out_free;
1905
1906         retval = copy_string_kernel(bprm->filename, bprm);
1907         if (retval < 0)
1908                 goto out_free;
1909         bprm->exec = bprm->p;
1910
1911         retval = copy_strings(bprm->envc, envp, bprm);
1912         if (retval < 0)
1913                 goto out_free;
1914
1915         retval = copy_strings(bprm->argc, argv, bprm);
1916         if (retval < 0)
1917                 goto out_free;
1918
1919         retval = bprm_execve(bprm, fd, filename, flags);
1920 out_free:
1921         free_bprm(bprm);
1922
1923 out_ret:
1924         putname(filename);
1925         return retval;
1926 }
1927
1928 int kernel_execve(const char *kernel_filename,
1929                   const char *const *argv, const char *const *envp)
1930 {
1931         struct filename *filename;
1932         struct linux_binprm *bprm;
1933         int fd = AT_FDCWD;
1934         int retval;
1935
1936         filename = getname_kernel(kernel_filename);
1937         if (IS_ERR(filename))
1938                 return PTR_ERR(filename);
1939
1940         bprm = alloc_bprm(fd, filename);
1941         if (IS_ERR(bprm)) {
1942                 retval = PTR_ERR(bprm);
1943                 goto out_ret;
1944         }
1945
1946         retval = count_strings_kernel(argv);
1947         if (retval < 0)
1948                 goto out_free;
1949         bprm->argc = retval;
1950
1951         retval = count_strings_kernel(envp);
1952         if (retval < 0)
1953                 goto out_free;
1954         bprm->envc = retval;
1955
1956         retval = bprm_stack_limits(bprm);
1957         if (retval < 0)
1958                 goto out_free;
1959
1960         retval = copy_string_kernel(bprm->filename, bprm);
1961         if (retval < 0)
1962                 goto out_free;
1963         bprm->exec = bprm->p;
1964
1965         retval = copy_strings_kernel(bprm->envc, envp, bprm);
1966         if (retval < 0)
1967                 goto out_free;
1968
1969         retval = copy_strings_kernel(bprm->argc, argv, bprm);
1970         if (retval < 0)
1971                 goto out_free;
1972
1973         retval = bprm_execve(bprm, fd, filename, 0);
1974 out_free:
1975         free_bprm(bprm);
1976 out_ret:
1977         putname(filename);
1978         return retval;
1979 }
1980
1981 static int do_execve(struct filename *filename,
1982         const char __user *const __user *__argv,
1983         const char __user *const __user *__envp)
1984 {
1985         struct user_arg_ptr argv = { .ptr.native = __argv };
1986         struct user_arg_ptr envp = { .ptr.native = __envp };
1987         return do_execveat_common(AT_FDCWD, filename, argv, envp, 0);
1988 }
1989
1990 static int do_execveat(int fd, struct filename *filename,
1991                 const char __user *const __user *__argv,
1992                 const char __user *const __user *__envp,
1993                 int flags)
1994 {
1995         struct user_arg_ptr argv = { .ptr.native = __argv };
1996         struct user_arg_ptr envp = { .ptr.native = __envp };
1997
1998         return do_execveat_common(fd, filename, argv, envp, flags);
1999 }
2000
2001 #ifdef CONFIG_COMPAT
2002 static int compat_do_execve(struct filename *filename,
2003         const compat_uptr_t __user *__argv,
2004         const compat_uptr_t __user *__envp)
2005 {
2006         struct user_arg_ptr argv = {
2007                 .is_compat = true,
2008                 .ptr.compat = __argv,
2009         };
2010         struct user_arg_ptr envp = {
2011                 .is_compat = true,
2012                 .ptr.compat = __envp,
2013         };
2014         return do_execveat_common(AT_FDCWD, filename, argv, envp, 0);
2015 }
2016
2017 static int compat_do_execveat(int fd, struct filename *filename,
2018                               const compat_uptr_t __user *__argv,
2019                               const compat_uptr_t __user *__envp,
2020                               int flags)
2021 {
2022         struct user_arg_ptr argv = {
2023                 .is_compat = true,
2024                 .ptr.compat = __argv,
2025         };
2026         struct user_arg_ptr envp = {
2027                 .is_compat = true,
2028                 .ptr.compat = __envp,
2029         };
2030         return do_execveat_common(fd, filename, argv, envp, flags);
2031 }
2032 #endif
2033
2034 void set_binfmt(struct linux_binfmt *new)
2035 {
2036         struct mm_struct *mm = current->mm;
2037
2038         if (mm->binfmt)
2039                 module_put(mm->binfmt->module);
2040
2041         mm->binfmt = new;
2042         if (new)
2043                 __module_get(new->module);
2044 }
2045 EXPORT_SYMBOL(set_binfmt);
2046
2047 /*
2048  * set_dumpable stores three-value SUID_DUMP_* into mm->flags.
2049  */
2050 void set_dumpable(struct mm_struct *mm, int value)
2051 {
2052         if (WARN_ON((unsigned)value > SUID_DUMP_ROOT))
2053                 return;
2054
2055         set_mask_bits(&mm->flags, MMF_DUMPABLE_MASK, value);
2056 }
2057
2058 SYSCALL_DEFINE3(execve,
2059                 const char __user *, filename,
2060                 const char __user *const __user *, argv,
2061                 const char __user *const __user *, envp)
2062 {
2063         return do_execve(getname(filename), argv, envp);
2064 }
2065
2066 SYSCALL_DEFINE5(execveat,
2067                 int, fd, const char __user *, filename,
2068                 const char __user *const __user *, argv,
2069                 const char __user *const __user *, envp,
2070                 int, flags)
2071 {
2072         int lookup_flags = (flags & AT_EMPTY_PATH) ? LOOKUP_EMPTY : 0;
2073
2074         return do_execveat(fd,
2075                            getname_flags(filename, lookup_flags, NULL),
2076                            argv, envp, flags);
2077 }
2078
2079 #ifdef CONFIG_COMPAT
2080 COMPAT_SYSCALL_DEFINE3(execve, const char __user *, filename,
2081         const compat_uptr_t __user *, argv,
2082         const compat_uptr_t __user *, envp)
2083 {
2084         return compat_do_execve(getname(filename), argv, envp);
2085 }
2086
2087 COMPAT_SYSCALL_DEFINE5(execveat, int, fd,
2088                        const char __user *, filename,
2089                        const compat_uptr_t __user *, argv,
2090                        const compat_uptr_t __user *, envp,
2091                        int,  flags)
2092 {
2093         int lookup_flags = (flags & AT_EMPTY_PATH) ? LOOKUP_EMPTY : 0;
2094
2095         return compat_do_execveat(fd,
2096                                   getname_flags(filename, lookup_flags, NULL),
2097                                   argv, envp, flags);
2098 }
2099 #endif