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