mm/mprotect.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *  mm/mprotect.c
   4  *
   5  *  (C) Copyright 1994 Linus Torvalds
   6  *  (C) Copyright 2002 Christoph Hellwig
   7  *
   8  *  Address space accounting code       <alan@lxorguk.ukuu.org.uk>
   9  *  (C) Copyright 2002 Red Hat Inc, All Rights Reserved
  10  */
  11
  12 #include <linux/pagewalk.h>
  13 #include <linux/hugetlb.h>
  14 #include <linux/shm.h>
  15 #include <linux/mman.h>
  16 #include <linux/fs.h>
  17 #include <linux/highmem.h>
  18 #include <linux/security.h>
  19 #include <linux/mempolicy.h>
  20 #include <linux/personality.h>
  21 #include <linux/syscalls.h>
  22 #include <linux/swap.h>
  23 #include <linux/swapops.h>
  24 #include <linux/mmu_notifier.h>
  25 #include <linux/migrate.h>
  26 #include <linux/perf_event.h>
  27 #include <linux/pkeys.h>
  28 #include <linux/ksm.h>
  29 #include <linux/uaccess.h>
  30 #include <linux/mm_inline.h>
  31 #include <linux/pgtable.h>
  32 #include <linux/sched/sysctl.h>
  33 #include <linux/userfaultfd_k.h>
  34 #include <linux/memory-tiers.h>
  35 #include <asm/cacheflush.h>
  36 #include <asm/mmu_context.h>
  37 #include <asm/tlbflush.h>
  38 #include <asm/tlb.h>
  39
  40 #include "internal.h"
  41
  42 bool can_change_pte_writable(struct vm_area_struct *vma, unsigned long addr,
  43                              pte_t pte)
  44 {
  45         struct page *page;
  46
  47         if (WARN_ON_ONCE(!(vma->vm_flags & VM_WRITE)))
  48                 return false;
  49
  50         /* Don't touch entries that are not even readable. */
  51         if (pte_protnone(pte))
  52                 return false;
  53
  54         /* Do we need write faults for softdirty tracking? */
  55         if (vma_soft_dirty_enabled(vma) && !pte_soft_dirty(pte))
  56                 return false;
  57
  58         /* Do we need write faults for uffd-wp tracking? */
  59         if (userfaultfd_pte_wp(vma, pte))
  60                 return false;
  61
  62         if (!(vma->vm_flags & VM_SHARED)) {
  63                 /*
  64                  * Writable MAP_PRIVATE mapping: We can only special-case on
  65                  * exclusive anonymous pages, because we know that our
  66                  * write-fault handler similarly would map them writable without
  67                  * any additional checks while holding the PT lock.
  68                  */
  69                 page = vm_normal_page(vma, addr, pte);
  70                 return page && PageAnon(page) && PageAnonExclusive(page);
  71         }
  72
  73         /*
  74          * Writable MAP_SHARED mapping: "clean" might indicate that the FS still
  75          * needs a real write-fault for writenotify
  76          * (see vma_wants_writenotify()). If "dirty", the assumption is that the
  77          * FS was already notified and we can simply mark the PTE writable
  78          * just like the write-fault handler would do.
  79          */
  80         return pte_dirty(pte);
  81 }
  82
  83 static unsigned long change_pte_range(struct mmu_gather *tlb,
  84                 struct vm_area_struct *vma, pmd_t *pmd, unsigned long addr,
  85                 unsigned long end, pgprot_t newprot, unsigned long cp_flags)
  86 {
  87         pte_t *pte, oldpte;
  88         spinlock_t *ptl;
  89         unsigned long pages = 0;
  90         int target_node = NUMA_NO_NODE;
  91         bool prot_numa = cp_flags & MM_CP_PROT_NUMA;
  92         bool uffd_wp = cp_flags & MM_CP_UFFD_WP;
  93         bool uffd_wp_resolve = cp_flags & MM_CP_UFFD_WP_RESOLVE;
  94
  95         tlb_change_page_size(tlb, PAGE_SIZE);
  96
  97         /*
  98          * Can be called with only the mmap_lock for reading by
  99          * prot_numa so we must check the pmd isn't constantly
 100          * changing from under us from pmd_none to pmd_trans_huge
 101          * and/or the other way around.
 102          */
 103         if (pmd_trans_unstable(pmd))
 104                 return 0;
 105
 106         /*
 107          * The pmd points to a regular pte so the pmd can't change
 108          * from under us even if the mmap_lock is only hold for
 109          * reading.
 110          */
 111         pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
 112
 113         /* Get target node for single threaded private VMAs */
 114         if (prot_numa && !(vma->vm_flags & VM_SHARED) &&
 115             atomic_read(&vma->vm_mm->mm_users) == 1)
 116                 target_node = numa_node_id();
 117
 118         flush_tlb_batched_pending(vma->vm_mm);
 119         arch_enter_lazy_mmu_mode();
 120         do {
 121                 oldpte = *pte;
 122                 if (pte_present(oldpte)) {
 123                         pte_t ptent;
 124
 125                         /*
 126                          * Avoid trapping faults against the zero or KSM
 127                          * pages. See similar comment in change_huge_pmd.
 128                          */
 129                         if (prot_numa) {
 130                                 struct page *page;
 131                                 int nid;
 132                                 bool toptier;
 133
 134                                 /* Avoid TLB flush if possible */
 135                                 if (pte_protnone(oldpte))
 136                                         continue;
 137
 138                                 page = vm_normal_page(vma, addr, oldpte);
 139                                 if (!page || is_zone_device_page(page) || PageKsm(page))
 140                                         continue;
 141
 142                                 /* Also skip shared copy-on-write pages */
 143                                 if (is_cow_mapping(vma->vm_flags) &&
 144                                     page_count(page) != 1)
 145                                         continue;
 146
 147                                 /*
 148                                  * While migration can move some dirty pages,
 149                                  * it cannot move them all from MIGRATE_ASYNC
 150                                  * context.
 151                                  */
 152                                 if (page_is_file_lru(page) && PageDirty(page))
 153                                         continue;
 154
 155                                 /*
 156                                  * Don't mess with PTEs if page is already on the node
 157                                  * a single-threaded process is running on.
 158                                  */
 159                                 nid = page_to_nid(page);
 160                                 if (target_node == nid)
 161                                         continue;
 162                                 toptier = node_is_toptier(nid);
 163
 164                                 /*
 165                                  * Skip scanning top tier node if normal numa
 166                                  * balancing is disabled
 167                                  */
 168                                 if (!(sysctl_numa_balancing_mode & NUMA_BALANCING_NORMAL) &&
 169                                     toptier)
 170                                         continue;
 171                                 if (sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING &&
 172                                     !toptier)
 173                                         xchg_page_access_time(page,
 174                                                 jiffies_to_msecs(jiffies));
 175                         }
 176
 177                         oldpte = ptep_modify_prot_start(vma, addr, pte);
 178                         ptent = pte_modify(oldpte, newprot);
 179
 180                         if (uffd_wp) {
 181                                 ptent = pte_wrprotect(ptent);
 182                                 ptent = pte_mkuffd_wp(ptent);
 183                         } else if (uffd_wp_resolve) {
 184                                 ptent = pte_clear_uffd_wp(ptent);
 185                         }
 186
 187                         /*
 188                          * In some writable, shared mappings, we might want
 189                          * to catch actual write access -- see
 190                          * vma_wants_writenotify().
 191                          *
 192                          * In all writable, private mappings, we have to
 193                          * properly handle COW.
 194                          *
 195                          * In both cases, we can sometimes still change PTEs
 196                          * writable and avoid the write-fault handler, for
 197                          * example, if a PTE is already dirty and no other
 198                          * COW or special handling is required.
 199                          */
 200                         if ((cp_flags & MM_CP_TRY_CHANGE_WRITABLE) &&
 201                             !pte_write(ptent) &&
 202                             can_change_pte_writable(vma, addr, ptent))
 203                                 ptent = pte_mkwrite(ptent);
 204
 205                         ptep_modify_prot_commit(vma, addr, pte, oldpte, ptent);
 206                         if (pte_needs_flush(oldpte, ptent))
 207                                 tlb_flush_pte_range(tlb, addr, PAGE_SIZE);
 208                         pages++;
 209                 } else if (is_swap_pte(oldpte)) {
 210                         swp_entry_t entry = pte_to_swp_entry(oldpte);
 211                         pte_t newpte;
 212
 213                         if (is_writable_migration_entry(entry)) {
 214                                 struct page *page = pfn_swap_entry_to_page(entry);
 215
 216                                 /*
 217                                  * A protection check is difficult so
 218                                  * just be safe and disable write
 219                                  */
 220                                 if (PageAnon(page))
 221                                         entry = make_readable_exclusive_migration_entry(
 222                                                              swp_offset(entry));
 223                                 else
 224                                         entry = make_readable_migration_entry(swp_offset(entry));
 225                                 newpte = swp_entry_to_pte(entry);
 226                                 if (pte_swp_soft_dirty(oldpte))
 227                                         newpte = pte_swp_mksoft_dirty(newpte);
 228                                 if (pte_swp_uffd_wp(oldpte))
 229                                         newpte = pte_swp_mkuffd_wp(newpte);
 230                         } else if (is_writable_device_private_entry(entry)) {
 231                                 /*
 232                                  * We do not preserve soft-dirtiness. See
 233                                  * copy_one_pte() for explanation.
 234                                  */
 235                                 entry = make_readable_device_private_entry(
 236                                                         swp_offset(entry));
 237                                 newpte = swp_entry_to_pte(entry);
 238                                 if (pte_swp_uffd_wp(oldpte))
 239                                         newpte = pte_swp_mkuffd_wp(newpte);
 240                         } else if (is_writable_device_exclusive_entry(entry)) {
 241                                 entry = make_readable_device_exclusive_entry(
 242                                                         swp_offset(entry));
 243                                 newpte = swp_entry_to_pte(entry);
 244                                 if (pte_swp_soft_dirty(oldpte))
 245                                         newpte = pte_swp_mksoft_dirty(newpte);
 246                                 if (pte_swp_uffd_wp(oldpte))
 247                                         newpte = pte_swp_mkuffd_wp(newpte);
 248                         } else if (is_pte_marker_entry(entry)) {
 249                                 /*
 250                                  * Ignore swapin errors unconditionally,
 251                                  * because any access should sigbus anyway.
 252                                  */
 253                                 if (is_swapin_error_entry(entry))
 254                                         continue;
 255                                 /*
 256                                  * If this is uffd-wp pte marker and we'd like
 257                                  * to unprotect it, drop it; the next page
 258                                  * fault will trigger without uffd trapping.
 259                                  */
 260                                 if (uffd_wp_resolve) {
 261                                         pte_clear(vma->vm_mm, addr, pte);
 262                                         pages++;
 263                                 }
 264                                 continue;
 265                         } else {
 266                                 newpte = oldpte;
 267                         }
 268
 269                         if (uffd_wp)
 270                                 newpte = pte_swp_mkuffd_wp(newpte);
 271                         else if (uffd_wp_resolve)
 272                                 newpte = pte_swp_clear_uffd_wp(newpte);
 273
 274                         if (!pte_same(oldpte, newpte)) {
 275                                 set_pte_at(vma->vm_mm, addr, pte, newpte);
 276                                 pages++;
 277                         }
 278                 } else {
 279                         /* It must be an none page, or what else?.. */
 280                         WARN_ON_ONCE(!pte_none(oldpte));
 281                         if (unlikely(uffd_wp && !vma_is_anonymous(vma))) {
 282                                 /*
 283                                  * For file-backed mem, we need to be able to
 284                                  * wr-protect a none pte, because even if the
 285                                  * pte is none, the page/swap cache could
 286                                  * exist.  Doing that by install a marker.
 287                                  */
 288                                 set_pte_at(vma->vm_mm, addr, pte,
 289                                            make_pte_marker(PTE_MARKER_UFFD_WP));
 290                                 pages++;
 291                         }
 292                 }
 293         } while (pte++, addr += PAGE_SIZE, addr != end);
 294         arch_leave_lazy_mmu_mode();
 295         pte_unmap_unlock(pte - 1, ptl);
 296
 297         return pages;
 298 }
 299
 300 /*
 301  * Used when setting automatic NUMA hinting protection where it is
 302  * critical that a numa hinting PMD is not confused with a bad PMD.
 303  */
 304 static inline int pmd_none_or_clear_bad_unless_trans_huge(pmd_t *pmd)
 305 {
 306         pmd_t pmdval = pmdp_get_lockless(pmd);
 307
 308         /* See pmd_none_or_trans_huge_or_clear_bad for info on barrier */
 309 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 310         barrier();
 311 #endif
 312
 313         if (pmd_none(pmdval))
 314                 return 1;
 315         if (pmd_trans_huge(pmdval))
 316                 return 0;
 317         if (unlikely(pmd_bad(pmdval))) {
 318                 pmd_clear_bad(pmd);
 319                 return 1;
 320         }
 321
 322         return 0;
 323 }
 324
 325 /* Return true if we're uffd wr-protecting file-backed memory, or false */
 326 static inline bool
 327 uffd_wp_protect_file(struct vm_area_struct *vma, unsigned long cp_flags)
 328 {
 329         return (cp_flags & MM_CP_UFFD_WP) && !vma_is_anonymous(vma);
 330 }
 331
 332 /*
 333  * If wr-protecting the range for file-backed, populate pgtable for the case
 334  * when pgtable is empty but page cache exists.  When {pte|pmd|...}_alloc()
 335  * failed it means no memory, we don't have a better option but stop.
 336  */
 337 #define  change_pmd_prepare(vma, pmd, cp_flags)                         \
 338         do {                                                            \
 339                 if (unlikely(uffd_wp_protect_file(vma, cp_flags))) {    \
 340                         if (WARN_ON_ONCE(pte_alloc(vma->vm_mm, pmd)))   \
 341                                 break;                                  \
 342                 }                                                       \
 343         } while (0)
 344 /*
 345  * This is the general pud/p4d/pgd version of change_pmd_prepare(). We need to
 346  * have separate change_pmd_prepare() because pte_alloc() returns 0 on success,
 347  * while {pmd|pud|p4d}_alloc() returns the valid pointer on success.
 348  */
 349 #define  change_prepare(vma, high, low, addr, cp_flags)                 \
 350         do {                                                            \
 351                 if (unlikely(uffd_wp_protect_file(vma, cp_flags))) {    \
 352                         low##_t *p = low##_alloc(vma->vm_mm, high, addr); \
 353                         if (WARN_ON_ONCE(p == NULL))                    \
 354                                 break;                                  \
 355                 }                                                       \
 356         } while (0)
 357
 358 static inline unsigned long change_pmd_range(struct mmu_gather *tlb,
 359                 struct vm_area_struct *vma, pud_t *pud, unsigned long addr,
 360                 unsigned long end, pgprot_t newprot, unsigned long cp_flags)
 361 {
 362         pmd_t *pmd;
 363         unsigned long next;
 364         unsigned long pages = 0;
 365         unsigned long nr_huge_updates = 0;
 366         struct mmu_notifier_range range;
 367
 368         range.start = 0;
 369
 370         pmd = pmd_offset(pud, addr);
 371         do {
 372                 unsigned long this_pages;
 373
 374                 next = pmd_addr_end(addr, end);
 375
 376                 change_pmd_prepare(vma, pmd, cp_flags);
 377                 /*
 378                  * Automatic NUMA balancing walks the tables with mmap_lock
 379                  * held for read. It's possible a parallel update to occur
 380                  * between pmd_trans_huge() and a pmd_none_or_clear_bad()
 381                  * check leading to a false positive and clearing.
 382                  * Hence, it's necessary to atomically read the PMD value
 383                  * for all the checks.
 384                  */
 385                 if (!is_swap_pmd(*pmd) && !pmd_devmap(*pmd) &&
 386                      pmd_none_or_clear_bad_unless_trans_huge(pmd))
 387                         goto next;
 388
 389                 /* invoke the mmu notifier if the pmd is populated */
 390                 if (!range.start) {
 391                         mmu_notifier_range_init(&range,
 392                                 MMU_NOTIFY_PROTECTION_VMA, 0,
 393                                 vma, vma->vm_mm, addr, end);
 394                         mmu_notifier_invalidate_range_start(&range);
 395                 }
 396
 397                 if (is_swap_pmd(*pmd) || pmd_trans_huge(*pmd) || pmd_devmap(*pmd)) {
 398                         if ((next - addr != HPAGE_PMD_SIZE) ||
 399                             uffd_wp_protect_file(vma, cp_flags)) {
 400                                 __split_huge_pmd(vma, pmd, addr, false, NULL);
 401                                 /*
 402                                  * For file-backed, the pmd could have been
 403                                  * cleared; make sure pmd populated if
 404                                  * necessary, then fall-through to pte level.
 405                                  */
 406                                 change_pmd_prepare(vma, pmd, cp_flags);
 407                         } else {
 408                                 /*
 409                                  * change_huge_pmd() does not defer TLB flushes,
 410                                  * so no need to propagate the tlb argument.
 411                                  */
 412                                 int nr_ptes = change_huge_pmd(tlb, vma, pmd,
 413                                                 addr, newprot, cp_flags);
 414
 415                                 if (nr_ptes) {
 416                                         if (nr_ptes == HPAGE_PMD_NR) {
 417                                                 pages += HPAGE_PMD_NR;
 418                                                 nr_huge_updates++;
 419                                         }
 420
 421                                         /* huge pmd was handled */
 422                                         goto next;
 423                                 }
 424                         }
 425                         /* fall through, the trans huge pmd just split */
 426                 }
 427                 this_pages = change_pte_range(tlb, vma, pmd, addr, next,
 428                                               newprot, cp_flags);
 429                 pages += this_pages;
 430 next:
 431                 cond_resched();
 432         } while (pmd++, addr = next, addr != end);
 433
 434         if (range.start)
 435                 mmu_notifier_invalidate_range_end(&range);
 436
 437         if (nr_huge_updates)
 438                 count_vm_numa_events(NUMA_HUGE_PTE_UPDATES, nr_huge_updates);
 439         return pages;
 440 }
 441
 442 static inline unsigned long change_pud_range(struct mmu_gather *tlb,
 443                 struct vm_area_struct *vma, p4d_t *p4d, unsigned long addr,
 444                 unsigned long end, pgprot_t newprot, unsigned long cp_flags)
 445 {
 446         pud_t *pud;
 447         unsigned long next;
 448         unsigned long pages = 0;
 449
 450         pud = pud_offset(p4d, addr);
 451         do {
 452                 next = pud_addr_end(addr, end);
 453                 change_prepare(vma, pud, pmd, addr, cp_flags);
 454                 if (pud_none_or_clear_bad(pud))
 455                         continue;
 456                 pages += change_pmd_range(tlb, vma, pud, addr, next, newprot,
 457                                           cp_flags);
 458         } while (pud++, addr = next, addr != end);
 459
 460         return pages;
 461 }
 462
 463 static inline unsigned long change_p4d_range(struct mmu_gather *tlb,
 464                 struct vm_area_struct *vma, pgd_t *pgd, unsigned long addr,
 465                 unsigned long end, pgprot_t newprot, unsigned long cp_flags)
 466 {
 467         p4d_t *p4d;
 468         unsigned long next;
 469         unsigned long pages = 0;
 470
 471         p4d = p4d_offset(pgd, addr);
 472         do {
 473                 next = p4d_addr_end(addr, end);
 474                 change_prepare(vma, p4d, pud, addr, cp_flags);
 475                 if (p4d_none_or_clear_bad(p4d))
 476                         continue;
 477                 pages += change_pud_range(tlb, vma, p4d, addr, next, newprot,
 478                                           cp_flags);
 479         } while (p4d++, addr = next, addr != end);
 480
 481         return pages;
 482 }
 483
 484 static unsigned long change_protection_range(struct mmu_gather *tlb,
 485                 struct vm_area_struct *vma, unsigned long addr,
 486                 unsigned long end, pgprot_t newprot, unsigned long cp_flags)
 487 {
 488         struct mm_struct *mm = vma->vm_mm;
 489         pgd_t *pgd;
 490         unsigned long next;
 491         unsigned long pages = 0;
 492
 493         BUG_ON(addr >= end);
 494         pgd = pgd_offset(mm, addr);
 495         tlb_start_vma(tlb, vma);
 496         do {
 497                 next = pgd_addr_end(addr, end);
 498                 change_prepare(vma, pgd, p4d, addr, cp_flags);
 499                 if (pgd_none_or_clear_bad(pgd))
 500                         continue;
 501                 pages += change_p4d_range(tlb, vma, pgd, addr, next, newprot,
 502                                           cp_flags);
 503         } while (pgd++, addr = next, addr != end);
 504
 505         tlb_end_vma(tlb, vma);
 506
 507         return pages;
 508 }
 509
 510 unsigned long change_protection(struct mmu_gather *tlb,
 511                        struct vm_area_struct *vma, unsigned long start,
 512                        unsigned long end, pgprot_t newprot,
 513                        unsigned long cp_flags)
 514 {
 515         unsigned long pages;
 516
 517         BUG_ON((cp_flags & MM_CP_UFFD_WP_ALL) == MM_CP_UFFD_WP_ALL);
 518
 519         if (is_vm_hugetlb_page(vma))
 520                 pages = hugetlb_change_protection(vma, start, end, newprot,
 521                                                   cp_flags);
 522         else
 523                 pages = change_protection_range(tlb, vma, start, end, newprot,
 524                                                 cp_flags);
 525
 526         return pages;
 527 }
 528
 529 static int prot_none_pte_entry(pte_t *pte, unsigned long addr,
 530                                unsigned long next, struct mm_walk *walk)
 531 {
 532         return pfn_modify_allowed(pte_pfn(*pte), *(pgprot_t *)(walk->private)) ?
 533                 0 : -EACCES;
 534 }
 535
 536 static int prot_none_hugetlb_entry(pte_t *pte, unsigned long hmask,
 537                                    unsigned long addr, unsigned long next,
 538                                    struct mm_walk *walk)
 539 {
 540         return pfn_modify_allowed(pte_pfn(*pte), *(pgprot_t *)(walk->private)) ?
 541                 0 : -EACCES;
 542 }
 543
 544 static int prot_none_test(unsigned long addr, unsigned long next,
 545                           struct mm_walk *walk)
 546 {
 547         return 0;
 548 }
 549
 550 static const struct mm_walk_ops prot_none_walk_ops = {
 551         .pte_entry              = prot_none_pte_entry,
 552         .hugetlb_entry          = prot_none_hugetlb_entry,
 553         .test_walk              = prot_none_test,
 554 };
 555
 556 int
 557 mprotect_fixup(struct mmu_gather *tlb, struct vm_area_struct *vma,
 558                struct vm_area_struct **pprev, unsigned long start,
 559                unsigned long end, unsigned long newflags)
 560 {
 561         struct mm_struct *mm = vma->vm_mm;
 562         unsigned long oldflags = vma->vm_flags;
 563         long nrpages = (end - start) >> PAGE_SHIFT;
 564         unsigned int mm_cp_flags = 0;
 565         unsigned long charged = 0;
 566         pgoff_t pgoff;
 567         int error;
 568
 569         if (newflags == oldflags) {
 570                 *pprev = vma;
 571                 return 0;
 572         }
 573
 574         /*
 575          * Do PROT_NONE PFN permission checks here when we can still
 576          * bail out without undoing a lot of state. This is a rather
 577          * uncommon case, so doesn't need to be very optimized.
 578          */
 579         if (arch_has_pfn_modify_check() &&
 580             (vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
 581             (newflags & VM_ACCESS_FLAGS) == 0) {
 582                 pgprot_t new_pgprot = vm_get_page_prot(newflags);
 583
 584                 error = walk_page_range(current->mm, start, end,
 585                                 &prot_none_walk_ops, &new_pgprot);
 586                 if (error)
 587                         return error;
 588         }
 589
 590         /*
 591          * If we make a private mapping writable we increase our commit;
 592          * but (without finer accounting) cannot reduce our commit if we
 593          * make it unwritable again. hugetlb mapping were accounted for
 594          * even if read-only so there is no need to account for them here
 595          */
 596         if (newflags & VM_WRITE) {
 597                 /* Check space limits when area turns into data. */
 598                 if (!may_expand_vm(mm, newflags, nrpages) &&
 599                                 may_expand_vm(mm, oldflags, nrpages))
 600                         return -ENOMEM;
 601                 if (!(oldflags & (VM_ACCOUNT|VM_WRITE|VM_HUGETLB|
 602                                                 VM_SHARED|VM_NORESERVE))) {
 603                         charged = nrpages;
 604                         if (security_vm_enough_memory_mm(mm, charged))
 605                                 return -ENOMEM;
 606                         newflags |= VM_ACCOUNT;
 607                 }
 608         }
 609
 610         /*
 611          * First try to merge with previous and/or next vma.
 612          */
 613         pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
 614         *pprev = vma_merge(mm, *pprev, start, end, newflags,
 615                            vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma),
 616                            vma->vm_userfaultfd_ctx, anon_vma_name(vma));
 617         if (*pprev) {
 618                 vma = *pprev;
 619                 VM_WARN_ON((vma->vm_flags ^ newflags) & ~VM_SOFTDIRTY);
 620                 goto success;
 621         }
 622
 623         *pprev = vma;
 624
 625         if (start != vma->vm_start) {
 626                 error = split_vma(mm, vma, start, 1);
 627                 if (error)
 628                         goto fail;
 629         }
 630
 631         if (end != vma->vm_end) {
 632                 error = split_vma(mm, vma, end, 0);
 633                 if (error)
 634                         goto fail;
 635         }
 636
 637 success:
 638         /*
 639          * vm_flags and vm_page_prot are protected by the mmap_lock
 640          * held in write mode.
 641          */
 642         vma->vm_flags = newflags;
 643         if (vma_wants_manual_pte_write_upgrade(vma))
 644                 mm_cp_flags |= MM_CP_TRY_CHANGE_WRITABLE;
 645         vma_set_page_prot(vma);
 646
 647         change_protection(tlb, vma, start, end, vma->vm_page_prot, mm_cp_flags);
 648
 649         /*
 650          * Private VM_LOCKED VMA becoming writable: trigger COW to avoid major
 651          * fault on access.
 652          */
 653         if ((oldflags & (VM_WRITE | VM_SHARED | VM_LOCKED)) == VM_LOCKED &&
 654                         (newflags & VM_WRITE)) {
 655                 populate_vma_page_range(vma, start, end, NULL);
 656         }
 657
 658         vm_stat_account(mm, oldflags, -nrpages);
 659         vm_stat_account(mm, newflags, nrpages);
 660         perf_event_mmap(vma);
 661         return 0;
 662
 663 fail:
 664         vm_unacct_memory(charged);
 665         return error;
 666 }
 667
 668 /*
 669  * pkey==-1 when doing a legacy mprotect()
 670  */
 671 static int do_mprotect_pkey(unsigned long start, size_t len,
 672                 unsigned long prot, int pkey)
 673 {
 674         unsigned long nstart, end, tmp, reqprot;
 675         struct vm_area_struct *vma, *prev;
 676         int error;
 677         const int grows = prot & (PROT_GROWSDOWN|PROT_GROWSUP);
 678         const bool rier = (current->personality & READ_IMPLIES_EXEC) &&
 679                                 (prot & PROT_READ);
 680         struct mmu_gather tlb;
 681         MA_STATE(mas, &current->mm->mm_mt, 0, 0);
 682
 683         start = untagged_addr(start);
 684
 685         prot &= ~(PROT_GROWSDOWN|PROT_GROWSUP);
 686         if (grows == (PROT_GROWSDOWN|PROT_GROWSUP)) /* can't be both */
 687                 return -EINVAL;
 688
 689         if (start & ~PAGE_MASK)
 690                 return -EINVAL;
 691         if (!len)
 692                 return 0;
 693         len = PAGE_ALIGN(len);
 694         end = start + len;
 695         if (end <= start)
 696                 return -ENOMEM;
 697         if (!arch_validate_prot(prot, start))
 698                 return -EINVAL;
 699
 700         reqprot = prot;
 701
 702         if (mmap_write_lock_killable(current->mm))
 703                 return -EINTR;
 704
 705         /*
 706          * If userspace did not allocate the pkey, do not let
 707          * them use it here.
 708          */
 709         error = -EINVAL;
 710         if ((pkey != -1) && !mm_pkey_is_allocated(current->mm, pkey))
 711                 goto out;
 712
 713         mas_set(&mas, start);
 714         vma = mas_find(&mas, ULONG_MAX);
 715         error = -ENOMEM;
 716         if (!vma)
 717                 goto out;
 718
 719         if (unlikely(grows & PROT_GROWSDOWN)) {
 720                 if (vma->vm_start >= end)
 721                         goto out;
 722                 start = vma->vm_start;
 723                 error = -EINVAL;
 724                 if (!(vma->vm_flags & VM_GROWSDOWN))
 725                         goto out;
 726         } else {
 727                 if (vma->vm_start > start)
 728                         goto out;
 729                 if (unlikely(grows & PROT_GROWSUP)) {
 730                         end = vma->vm_end;
 731                         error = -EINVAL;
 732                         if (!(vma->vm_flags & VM_GROWSUP))
 733                                 goto out;
 734                 }
 735         }
 736
 737         if (start > vma->vm_start)
 738                 prev = vma;
 739         else
 740                 prev = mas_prev(&mas, 0);
 741
 742         tlb_gather_mmu(&tlb, current->mm);
 743         for (nstart = start ; ; ) {
 744                 unsigned long mask_off_old_flags;
 745                 unsigned long newflags;
 746                 int new_vma_pkey;
 747
 748                 /* Here we know that vma->vm_start <= nstart < vma->vm_end. */
 749
 750                 /* Does the application expect PROT_READ to imply PROT_EXEC */
 751                 if (rier && (vma->vm_flags & VM_MAYEXEC))
 752                         prot |= PROT_EXEC;
 753
 754                 /*
 755                  * Each mprotect() call explicitly passes r/w/x permissions.
 756                  * If a permission is not passed to mprotect(), it must be
 757                  * cleared from the VMA.
 758                  */
 759                 mask_off_old_flags = VM_ACCESS_FLAGS | VM_FLAGS_CLEAR;
 760
 761                 new_vma_pkey = arch_override_mprotect_pkey(vma, prot, pkey);
 762                 newflags = calc_vm_prot_bits(prot, new_vma_pkey);
 763                 newflags |= (vma->vm_flags & ~mask_off_old_flags);
 764
 765                 /* newflags >> 4 shift VM_MAY% in place of VM_% */
 766                 if ((newflags & ~(newflags >> 4)) & VM_ACCESS_FLAGS) {
 767                         error = -EACCES;
 768                         break;
 769                 }
 770
 771                 /* Allow architectures to sanity-check the new flags */
 772                 if (!arch_validate_flags(newflags)) {
 773                         error = -EINVAL;
 774                         break;
 775                 }
 776
 777                 error = security_file_mprotect(vma, reqprot, prot);
 778                 if (error)
 779                         break;
 780
 781                 tmp = vma->vm_end;
 782                 if (tmp > end)
 783                         tmp = end;
 784
 785                 if (vma->vm_ops && vma->vm_ops->mprotect) {
 786                         error = vma->vm_ops->mprotect(vma, nstart, tmp, newflags);
 787                         if (error)
 788                                 break;
 789                 }
 790
 791                 error = mprotect_fixup(&tlb, vma, &prev, nstart, tmp, newflags);
 792                 if (error)
 793                         break;
 794
 795                 nstart = tmp;
 796
 797                 if (nstart < prev->vm_end)
 798                         nstart = prev->vm_end;
 799                 if (nstart >= end)
 800                         break;
 801
 802                 vma = find_vma(current->mm, prev->vm_end);
 803                 if (!vma || vma->vm_start != nstart) {
 804                         error = -ENOMEM;
 805                         break;
 806                 }
 807                 prot = reqprot;
 808         }
 809         tlb_finish_mmu(&tlb);
 810 out:
 811         mmap_write_unlock(current->mm);
 812         return error;
 813 }
 814
 815 SYSCALL_DEFINE3(mprotect, unsigned long, start, size_t, len,
 816                 unsigned long, prot)
 817 {
 818         return do_mprotect_pkey(start, len, prot, -1);
 819 }
 820
 821 #ifdef CONFIG_ARCH_HAS_PKEYS
 822
 823 SYSCALL_DEFINE4(pkey_mprotect, unsigned long, start, size_t, len,
 824                 unsigned long, prot, int, pkey)
 825 {
 826         return do_mprotect_pkey(start, len, prot, pkey);
 827 }
 828
 829 SYSCALL_DEFINE2(pkey_alloc, unsigned long, flags, unsigned long, init_val)
 830 {
 831         int pkey;
 832         int ret;
 833
 834         /* No flags supported yet. */
 835         if (flags)
 836                 return -EINVAL;
 837         /* check for unsupported init values */
 838         if (init_val & ~PKEY_ACCESS_MASK)
 839                 return -EINVAL;
 840
 841         mmap_write_lock(current->mm);
 842         pkey = mm_pkey_alloc(current->mm);
 843
 844         ret = -ENOSPC;
 845         if (pkey == -1)
 846                 goto out;
 847
 848         ret = arch_set_user_pkey_access(current, pkey, init_val);
 849         if (ret) {
 850                 mm_pkey_free(current->mm, pkey);
 851                 goto out;
 852         }
 853         ret = pkey;
 854 out:
 855         mmap_write_unlock(current->mm);
 856         return ret;
 857 }
 858
 859 SYSCALL_DEFINE1(pkey_free, int, pkey)
 860 {
 861         int ret;
 862
 863         mmap_write_lock(current->mm);
 864         ret = mm_pkey_free(current->mm, pkey);
 865         mmap_write_unlock(current->mm);
 866
 867         /*
 868          * We could provide warnings or errors if any VMA still
 869          * has the pkey set here.
 870          */
 871         return ret;
 872 }
 873
 874 #endif /* CONFIG_ARCH_HAS_PKEYS */