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 <uapi/linux/mman.h>
  36 #include <asm/cacheflush.h>
  37 #include <asm/mmu_context.h>
  38 #include <asm/tlbflush.h>
  39 #include <asm/tlb.h>
  40
  41 #include "internal.h"
  42
  43 bool can_change_pte_writable(struct vm_area_struct *vma, unsigned long addr,
  44                              pte_t pte)
  45 {
  46         struct page *page;
  47
  48         if (WARN_ON_ONCE(!(vma->vm_flags & VM_WRITE)))
  49                 return false;
  50
  51         /* Don't touch entries that are not even readable. */
  52         if (pte_protnone(pte))
  53                 return false;
  54
  55         /* Do we need write faults for softdirty tracking? */
  56         if (vma_soft_dirty_enabled(vma) && !pte_soft_dirty(pte))
  57                 return false;
  58
  59         /* Do we need write faults for uffd-wp tracking? */
  60         if (userfaultfd_pte_wp(vma, pte))
  61                 return false;
  62
  63         if (!(vma->vm_flags & VM_SHARED)) {
  64                 /*
  65                  * Writable MAP_PRIVATE mapping: We can only special-case on
  66                  * exclusive anonymous pages, because we know that our
  67                  * write-fault handler similarly would map them writable without
  68                  * any additional checks while holding the PT lock.
  69                  */
  70                 page = vm_normal_page(vma, addr, pte);
  71                 return page && PageAnon(page) && PageAnonExclusive(page);
  72         }
  73
  74         /*
  75          * Writable MAP_SHARED mapping: "clean" might indicate that the FS still
  76          * needs a real write-fault for writenotify
  77          * (see vma_wants_writenotify()). If "dirty", the assumption is that the
  78          * FS was already notified and we can simply mark the PTE writable
  79          * just like the write-fault handler would do.
  80          */
  81         return pte_dirty(pte);
  82 }
  83
  84 static long change_pte_range(struct mmu_gather *tlb,
  85                 struct vm_area_struct *vma, pmd_t *pmd, unsigned long addr,
  86                 unsigned long end, pgprot_t newprot, unsigned long cp_flags)
  87 {
  88         pte_t *pte, oldpte;
  89         spinlock_t *ptl;
  90         long pages = 0;
  91         int target_node = NUMA_NO_NODE;
  92         bool prot_numa = cp_flags & MM_CP_PROT_NUMA;
  93         bool uffd_wp = cp_flags & MM_CP_UFFD_WP;
  94         bool uffd_wp_resolve = cp_flags & MM_CP_UFFD_WP_RESOLVE;
  95
  96         tlb_change_page_size(tlb, PAGE_SIZE);
  97         pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
  98         if (!pte)
  99                 return -EAGAIN;
 100
 101         /* Get target node for single threaded private VMAs */
 102         if (prot_numa && !(vma->vm_flags & VM_SHARED) &&
 103             atomic_read(&vma->vm_mm->mm_users) == 1)
 104                 target_node = numa_node_id();
 105
 106         flush_tlb_batched_pending(vma->vm_mm);
 107         arch_enter_lazy_mmu_mode();
 108         do {
 109                 oldpte = ptep_get(pte);
 110                 if (pte_present(oldpte)) {
 111                         pte_t ptent;
 112
 113                         /*
 114                          * Avoid trapping faults against the zero or KSM
 115                          * pages. See similar comment in change_huge_pmd.
 116                          */
 117                         if (prot_numa) {
 118                                 struct folio *folio;
 119                                 int nid;
 120                                 bool toptier;
 121
 122                                 /* Avoid TLB flush if possible */
 123                                 if (pte_protnone(oldpte))
 124                                         continue;
 125
 126                                 folio = vm_normal_folio(vma, addr, oldpte);
 127                                 if (!folio || folio_is_zone_device(folio) ||
 128                                     folio_test_ksm(folio))
 129                                         continue;
 130
 131                                 /* Also skip shared copy-on-write pages */
 132                                 if (is_cow_mapping(vma->vm_flags) &&
 133                                     (folio_maybe_dma_pinned(folio) ||
 134                                      folio_likely_mapped_shared(folio)))
 135                                         continue;
 136
 137                                 /*
 138                                  * While migration can move some dirty pages,
 139                                  * it cannot move them all from MIGRATE_ASYNC
 140                                  * context.
 141                                  */
 142                                 if (folio_is_file_lru(folio) &&
 143                                     folio_test_dirty(folio))
 144                                         continue;
 145
 146                                 /*
 147                                  * Don't mess with PTEs if page is already on the node
 148                                  * a single-threaded process is running on.
 149                                  */
 150                                 nid = folio_nid(folio);
 151                                 if (target_node == nid)
 152                                         continue;
 153                                 toptier = node_is_toptier(nid);
 154
 155                                 /*
 156                                  * Skip scanning top tier node if normal numa
 157                                  * balancing is disabled
 158                                  */
 159                                 if (!(sysctl_numa_balancing_mode & NUMA_BALANCING_NORMAL) &&
 160                                     toptier)
 161                                         continue;
 162                                 if (sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING &&
 163                                     !toptier)
 164                                         folio_xchg_access_time(folio,
 165                                                 jiffies_to_msecs(jiffies));
 166                         }
 167
 168                         oldpte = ptep_modify_prot_start(vma, addr, pte);
 169                         ptent = pte_modify(oldpte, newprot);
 170
 171                         if (uffd_wp)
 172                                 ptent = pte_mkuffd_wp(ptent);
 173                         else if (uffd_wp_resolve)
 174                                 ptent = pte_clear_uffd_wp(ptent);
 175
 176                         /*
 177                          * In some writable, shared mappings, we might want
 178                          * to catch actual write access -- see
 179                          * vma_wants_writenotify().
 180                          *
 181                          * In all writable, private mappings, we have to
 182                          * properly handle COW.
 183                          *
 184                          * In both cases, we can sometimes still change PTEs
 185                          * writable and avoid the write-fault handler, for
 186                          * example, if a PTE is already dirty and no other
 187                          * COW or special handling is required.
 188                          */
 189                         if ((cp_flags & MM_CP_TRY_CHANGE_WRITABLE) &&
 190                             !pte_write(ptent) &&
 191                             can_change_pte_writable(vma, addr, ptent))
 192                                 ptent = pte_mkwrite(ptent, vma);
 193
 194                         ptep_modify_prot_commit(vma, addr, pte, oldpte, ptent);
 195                         if (pte_needs_flush(oldpte, ptent))
 196                                 tlb_flush_pte_range(tlb, addr, PAGE_SIZE);
 197                         pages++;
 198                 } else if (is_swap_pte(oldpte)) {
 199                         swp_entry_t entry = pte_to_swp_entry(oldpte);
 200                         pte_t newpte;
 201
 202                         if (is_writable_migration_entry(entry)) {
 203                                 struct folio *folio = pfn_swap_entry_folio(entry);
 204
 205                                 /*
 206                                  * A protection check is difficult so
 207                                  * just be safe and disable write
 208                                  */
 209                                 if (folio_test_anon(folio))
 210                                         entry = make_readable_exclusive_migration_entry(
 211                                                              swp_offset(entry));
 212                                 else
 213                                         entry = make_readable_migration_entry(swp_offset(entry));
 214                                 newpte = swp_entry_to_pte(entry);
 215                                 if (pte_swp_soft_dirty(oldpte))
 216                                         newpte = pte_swp_mksoft_dirty(newpte);
 217                         } else if (is_writable_device_private_entry(entry)) {
 218                                 /*
 219                                  * We do not preserve soft-dirtiness. See
 220                                  * copy_nonpresent_pte() for explanation.
 221                                  */
 222                                 entry = make_readable_device_private_entry(
 223                                                         swp_offset(entry));
 224                                 newpte = swp_entry_to_pte(entry);
 225                                 if (pte_swp_uffd_wp(oldpte))
 226                                         newpte = pte_swp_mkuffd_wp(newpte);
 227                         } else if (is_writable_device_exclusive_entry(entry)) {
 228                                 entry = make_readable_device_exclusive_entry(
 229                                                         swp_offset(entry));
 230                                 newpte = swp_entry_to_pte(entry);
 231                                 if (pte_swp_soft_dirty(oldpte))
 232                                         newpte = pte_swp_mksoft_dirty(newpte);
 233                                 if (pte_swp_uffd_wp(oldpte))
 234                                         newpte = pte_swp_mkuffd_wp(newpte);
 235                         } else if (is_pte_marker_entry(entry)) {
 236                                 /*
 237                                  * Ignore error swap entries unconditionally,
 238                                  * because any access should sigbus anyway.
 239                                  */
 240                                 if (is_poisoned_swp_entry(entry))
 241                                         continue;
 242                                 /*
 243                                  * If this is uffd-wp pte marker and we'd like
 244                                  * to unprotect it, drop it; the next page
 245                                  * fault will trigger without uffd trapping.
 246                                  */
 247                                 if (uffd_wp_resolve) {
 248                                         pte_clear(vma->vm_mm, addr, pte);
 249                                         pages++;
 250                                 }
 251                                 continue;
 252                         } else {
 253                                 newpte = oldpte;
 254                         }
 255
 256                         if (uffd_wp)
 257                                 newpte = pte_swp_mkuffd_wp(newpte);
 258                         else if (uffd_wp_resolve)
 259                                 newpte = pte_swp_clear_uffd_wp(newpte);
 260
 261                         if (!pte_same(oldpte, newpte)) {
 262                                 set_pte_at(vma->vm_mm, addr, pte, newpte);
 263                                 pages++;
 264                         }
 265                 } else {
 266                         /* It must be an none page, or what else?.. */
 267                         WARN_ON_ONCE(!pte_none(oldpte));
 268
 269                         /*
 270                          * Nobody plays with any none ptes besides
 271                          * userfaultfd when applying the protections.
 272                          */
 273                         if (likely(!uffd_wp))
 274                                 continue;
 275
 276                         if (userfaultfd_wp_use_markers(vma)) {
 277                                 /*
 278                                  * For file-backed mem, we need to be able to
 279                                  * wr-protect a none pte, because even if the
 280                                  * pte is none, the page/swap cache could
 281                                  * exist.  Doing that by install a marker.
 282                                  */
 283                                 set_pte_at(vma->vm_mm, addr, pte,
 284                                            make_pte_marker(PTE_MARKER_UFFD_WP));
 285                                 pages++;
 286                         }
 287                 }
 288         } while (pte++, addr += PAGE_SIZE, addr != end);
 289         arch_leave_lazy_mmu_mode();
 290         pte_unmap_unlock(pte - 1, ptl);
 291
 292         return pages;
 293 }
 294
 295 /*
 296  * Return true if we want to split THPs into PTE mappings in change
 297  * protection procedure, false otherwise.
 298  */
 299 static inline bool
 300 pgtable_split_needed(struct vm_area_struct *vma, unsigned long cp_flags)
 301 {
 302         /*
 303          * pte markers only resides in pte level, if we need pte markers,
 304          * we need to split.  We cannot wr-protect shmem thp because file
 305          * thp is handled differently when split by erasing the pmd so far.
 306          */
 307         return (cp_flags & MM_CP_UFFD_WP) && !vma_is_anonymous(vma);
 308 }
 309
 310 /*
 311  * Return true if we want to populate pgtables in change protection
 312  * procedure, false otherwise
 313  */
 314 static inline bool
 315 pgtable_populate_needed(struct vm_area_struct *vma, unsigned long cp_flags)
 316 {
 317         /* If not within ioctl(UFFDIO_WRITEPROTECT), then don't bother */
 318         if (!(cp_flags & MM_CP_UFFD_WP))
 319                 return false;
 320
 321         /* Populate if the userfaultfd mode requires pte markers */
 322         return userfaultfd_wp_use_markers(vma);
 323 }
 324
 325 /*
 326  * Populate the pgtable underneath for whatever reason if requested.
 327  * When {pte|pmd|...}_alloc() failed we treat it the same way as pgtable
 328  * allocation failures during page faults by kicking OOM and returning
 329  * error.
 330  */
 331 #define  change_pmd_prepare(vma, pmd, cp_flags)                         \
 332         ({                                                              \
 333                 long err = 0;                                           \
 334                 if (unlikely(pgtable_populate_needed(vma, cp_flags))) { \
 335                         if (pte_alloc(vma->vm_mm, pmd))                 \
 336                                 err = -ENOMEM;                          \
 337                 }                                                       \
 338                 err;                                                    \
 339         })
 340
 341 /*
 342  * This is the general pud/p4d/pgd version of change_pmd_prepare(). We need to
 343  * have separate change_pmd_prepare() because pte_alloc() returns 0 on success,
 344  * while {pmd|pud|p4d}_alloc() returns the valid pointer on success.
 345  */
 346 #define  change_prepare(vma, high, low, addr, cp_flags)                 \
 347           ({                                                            \
 348                 long err = 0;                                           \
 349                 if (unlikely(pgtable_populate_needed(vma, cp_flags))) { \
 350                         low##_t *p = low##_alloc(vma->vm_mm, high, addr); \
 351                         if (p == NULL)                                  \
 352                                 err = -ENOMEM;                          \
 353                 }                                                       \
 354                 err;                                                    \
 355         })
 356
 357 static inline long change_pmd_range(struct mmu_gather *tlb,
 358                 struct vm_area_struct *vma, pud_t *pud, unsigned long addr,
 359                 unsigned long end, pgprot_t newprot, unsigned long cp_flags)
 360 {
 361         pmd_t *pmd;
 362         unsigned long next;
 363         long pages = 0;
 364         unsigned long nr_huge_updates = 0;
 365         struct mmu_notifier_range range;
 366
 367         range.start = 0;
 368
 369         pmd = pmd_offset(pud, addr);
 370         do {
 371                 long ret;
 372                 pmd_t _pmd;
 373 again:
 374                 next = pmd_addr_end(addr, end);
 375
 376                 ret = change_pmd_prepare(vma, pmd, cp_flags);
 377                 if (ret) {
 378                         pages = ret;
 379                         break;
 380                 }
 381
 382                 if (pmd_none(*pmd))
 383                         goto next;
 384
 385                 /* invoke the mmu notifier if the pmd is populated */
 386                 if (!range.start) {
 387                         mmu_notifier_range_init(&range,
 388                                 MMU_NOTIFY_PROTECTION_VMA, 0,
 389                                 vma->vm_mm, addr, end);
 390                         mmu_notifier_invalidate_range_start(&range);
 391                 }
 392
 393                 _pmd = pmdp_get_lockless(pmd);
 394                 if (is_swap_pmd(_pmd) || pmd_trans_huge(_pmd) || pmd_devmap(_pmd)) {
 395                         if ((next - addr != HPAGE_PMD_SIZE) ||
 396                             pgtable_split_needed(vma, cp_flags)) {
 397                                 __split_huge_pmd(vma, pmd, addr, false, NULL);
 398                                 /*
 399                                  * For file-backed, the pmd could have been
 400                                  * cleared; make sure pmd populated if
 401                                  * necessary, then fall-through to pte level.
 402                                  */
 403                                 ret = change_pmd_prepare(vma, pmd, cp_flags);
 404                                 if (ret) {
 405                                         pages = ret;
 406                                         break;
 407                                 }
 408                         } else {
 409                                 ret = change_huge_pmd(tlb, vma, pmd,
 410                                                 addr, newprot, cp_flags);
 411                                 if (ret) {
 412                                         if (ret == HPAGE_PMD_NR) {
 413                                                 pages += HPAGE_PMD_NR;
 414                                                 nr_huge_updates++;
 415                                         }
 416
 417                                         /* huge pmd was handled */
 418                                         goto next;
 419                                 }
 420                         }
 421                         /* fall through, the trans huge pmd just split */
 422                 }
 423
 424                 ret = change_pte_range(tlb, vma, pmd, addr, next, newprot,
 425                                        cp_flags);
 426                 if (ret < 0)
 427                         goto again;
 428                 pages += ret;
 429 next:
 430                 cond_resched();
 431         } while (pmd++, addr = next, addr != end);
 432
 433         if (range.start)
 434                 mmu_notifier_invalidate_range_end(&range);
 435
 436         if (nr_huge_updates)
 437                 count_vm_numa_events(NUMA_HUGE_PTE_UPDATES, nr_huge_updates);
 438         return pages;
 439 }
 440
 441 static inline long change_pud_range(struct mmu_gather *tlb,
 442                 struct vm_area_struct *vma, p4d_t *p4d, unsigned long addr,
 443                 unsigned long end, pgprot_t newprot, unsigned long cp_flags)
 444 {
 445         pud_t *pud;
 446         unsigned long next;
 447         long pages = 0, ret;
 448
 449         pud = pud_offset(p4d, addr);
 450         do {
 451                 next = pud_addr_end(addr, end);
 452                 ret = change_prepare(vma, pud, pmd, addr, cp_flags);
 453                 if (ret)
 454                         return ret;
 455                 if (pud_none_or_clear_bad(pud))
 456                         continue;
 457                 pages += change_pmd_range(tlb, vma, pud, addr, next, newprot,
 458                                           cp_flags);
 459         } while (pud++, addr = next, addr != end);
 460
 461         return pages;
 462 }
 463
 464 static inline long change_p4d_range(struct mmu_gather *tlb,
 465                 struct vm_area_struct *vma, pgd_t *pgd, unsigned long addr,
 466                 unsigned long end, pgprot_t newprot, unsigned long cp_flags)
 467 {
 468         p4d_t *p4d;
 469         unsigned long next;
 470         long pages = 0, ret;
 471
 472         p4d = p4d_offset(pgd, addr);
 473         do {
 474                 next = p4d_addr_end(addr, end);
 475                 ret = change_prepare(vma, p4d, pud, addr, cp_flags);
 476                 if (ret)
 477                         return ret;
 478                 if (p4d_none_or_clear_bad(p4d))
 479                         continue;
 480                 pages += change_pud_range(tlb, vma, p4d, addr, next, newprot,
 481                                           cp_flags);
 482         } while (p4d++, addr = next, addr != end);
 483
 484         return pages;
 485 }
 486
 487 static long change_protection_range(struct mmu_gather *tlb,
 488                 struct vm_area_struct *vma, unsigned long addr,
 489                 unsigned long end, pgprot_t newprot, unsigned long cp_flags)
 490 {
 491         struct mm_struct *mm = vma->vm_mm;
 492         pgd_t *pgd;
 493         unsigned long next;
 494         long pages = 0, ret;
 495
 496         BUG_ON(addr >= end);
 497         pgd = pgd_offset(mm, addr);
 498         tlb_start_vma(tlb, vma);
 499         do {
 500                 next = pgd_addr_end(addr, end);
 501                 ret = change_prepare(vma, pgd, p4d, addr, cp_flags);
 502                 if (ret) {
 503                         pages = ret;
 504                         break;
 505                 }
 506                 if (pgd_none_or_clear_bad(pgd))
 507                         continue;
 508                 pages += change_p4d_range(tlb, vma, pgd, addr, next, newprot,
 509                                           cp_flags);
 510         } while (pgd++, addr = next, addr != end);
 511
 512         tlb_end_vma(tlb, vma);
 513
 514         return pages;
 515 }
 516
 517 long change_protection(struct mmu_gather *tlb,
 518                        struct vm_area_struct *vma, unsigned long start,
 519                        unsigned long end, unsigned long cp_flags)
 520 {
 521         pgprot_t newprot = vma->vm_page_prot;
 522         long pages;
 523
 524         BUG_ON((cp_flags & MM_CP_UFFD_WP_ALL) == MM_CP_UFFD_WP_ALL);
 525
 526 #ifdef CONFIG_NUMA_BALANCING
 527         /*
 528          * Ordinary protection updates (mprotect, uffd-wp, softdirty tracking)
 529          * are expected to reflect their requirements via VMA flags such that
 530          * vma_set_page_prot() will adjust vma->vm_page_prot accordingly.
 531          */
 532         if (cp_flags & MM_CP_PROT_NUMA)
 533                 newprot = PAGE_NONE;
 534 #else
 535         WARN_ON_ONCE(cp_flags & MM_CP_PROT_NUMA);
 536 #endif
 537
 538         if (is_vm_hugetlb_page(vma))
 539                 pages = hugetlb_change_protection(vma, start, end, newprot,
 540                                                   cp_flags);
 541         else
 542                 pages = change_protection_range(tlb, vma, start, end, newprot,
 543                                                 cp_flags);
 544
 545         return pages;
 546 }
 547
 548 static int prot_none_pte_entry(pte_t *pte, unsigned long addr,
 549                                unsigned long next, struct mm_walk *walk)
 550 {
 551         return pfn_modify_allowed(pte_pfn(ptep_get(pte)),
 552                                   *(pgprot_t *)(walk->private)) ?
 553                 0 : -EACCES;
 554 }
 555
 556 static int prot_none_hugetlb_entry(pte_t *pte, unsigned long hmask,
 557                                    unsigned long addr, unsigned long next,
 558                                    struct mm_walk *walk)
 559 {
 560         return pfn_modify_allowed(pte_pfn(ptep_get(pte)),
 561                                   *(pgprot_t *)(walk->private)) ?
 562                 0 : -EACCES;
 563 }
 564
 565 static int prot_none_test(unsigned long addr, unsigned long next,
 566                           struct mm_walk *walk)
 567 {
 568         return 0;
 569 }
 570
 571 static const struct mm_walk_ops prot_none_walk_ops = {
 572         .pte_entry              = prot_none_pte_entry,
 573         .hugetlb_entry          = prot_none_hugetlb_entry,
 574         .test_walk              = prot_none_test,
 575         .walk_lock              = PGWALK_WRLOCK,
 576 };
 577
 578 int
 579 mprotect_fixup(struct vma_iterator *vmi, struct mmu_gather *tlb,
 580                struct vm_area_struct *vma, struct vm_area_struct **pprev,
 581                unsigned long start, unsigned long end, unsigned long newflags)
 582 {
 583         struct mm_struct *mm = vma->vm_mm;
 584         unsigned long oldflags = vma->vm_flags;
 585         long nrpages = (end - start) >> PAGE_SHIFT;
 586         unsigned int mm_cp_flags = 0;
 587         unsigned long charged = 0;
 588         int error;
 589
 590         if (newflags == oldflags) {
 591                 *pprev = vma;
 592                 return 0;
 593         }
 594
 595         /*
 596          * Do PROT_NONE PFN permission checks here when we can still
 597          * bail out without undoing a lot of state. This is a rather
 598          * uncommon case, so doesn't need to be very optimized.
 599          */
 600         if (arch_has_pfn_modify_check() &&
 601             (vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
 602             (newflags & VM_ACCESS_FLAGS) == 0) {
 603                 pgprot_t new_pgprot = vm_get_page_prot(newflags);
 604
 605                 error = walk_page_range(current->mm, start, end,
 606                                 &prot_none_walk_ops, &new_pgprot);
 607                 if (error)
 608                         return error;
 609         }
 610
 611         /*
 612          * If we make a private mapping writable we increase our commit;
 613          * but (without finer accounting) cannot reduce our commit if we
 614          * make it unwritable again except in the anonymous case where no
 615          * anon_vma has yet to be assigned.
 616          *
 617          * hugetlb mapping were accounted for even if read-only so there is
 618          * no need to account for them here.
 619          */
 620         if (newflags & VM_WRITE) {
 621                 /* Check space limits when area turns into data. */
 622                 if (!may_expand_vm(mm, newflags, nrpages) &&
 623                                 may_expand_vm(mm, oldflags, nrpages))
 624                         return -ENOMEM;
 625                 if (!(oldflags & (VM_ACCOUNT|VM_WRITE|VM_HUGETLB|
 626                                                 VM_SHARED|VM_NORESERVE))) {
 627                         charged = nrpages;
 628                         if (security_vm_enough_memory_mm(mm, charged))
 629                                 return -ENOMEM;
 630                         newflags |= VM_ACCOUNT;
 631                 }
 632         } else if ((oldflags & VM_ACCOUNT) && vma_is_anonymous(vma) &&
 633                    !vma->anon_vma) {
 634                 newflags &= ~VM_ACCOUNT;
 635         }
 636
 637         vma = vma_modify_flags(vmi, *pprev, vma, start, end, newflags);
 638         if (IS_ERR(vma)) {
 639                 error = PTR_ERR(vma);
 640                 goto fail;
 641         }
 642
 643         *pprev = vma;
 644
 645         /*
 646          * vm_flags and vm_page_prot are protected by the mmap_lock
 647          * held in write mode.
 648          */
 649         vma_start_write(vma);
 650         vm_flags_reset(vma, newflags);
 651         if (vma_wants_manual_pte_write_upgrade(vma))
 652                 mm_cp_flags |= MM_CP_TRY_CHANGE_WRITABLE;
 653         vma_set_page_prot(vma);
 654
 655         change_protection(tlb, vma, start, end, mm_cp_flags);
 656
 657         if ((oldflags & VM_ACCOUNT) && !(newflags & VM_ACCOUNT))
 658                 vm_unacct_memory(nrpages);
 659
 660         /*
 661          * Private VM_LOCKED VMA becoming writable: trigger COW to avoid major
 662          * fault on access.
 663          */
 664         if ((oldflags & (VM_WRITE | VM_SHARED | VM_LOCKED)) == VM_LOCKED &&
 665                         (newflags & VM_WRITE)) {
 666                 populate_vma_page_range(vma, start, end, NULL);
 667         }
 668
 669         vm_stat_account(mm, oldflags, -nrpages);
 670         vm_stat_account(mm, newflags, nrpages);
 671         perf_event_mmap(vma);
 672         return 0;
 673
 674 fail:
 675         vm_unacct_memory(charged);
 676         return error;
 677 }
 678
 679 /*
 680  * pkey==-1 when doing a legacy mprotect()
 681  */
 682 static int do_mprotect_pkey(unsigned long start, size_t len,
 683                 unsigned long prot, int pkey)
 684 {
 685         unsigned long nstart, end, tmp, reqprot;
 686         struct vm_area_struct *vma, *prev;
 687         int error;
 688         const int grows = prot & (PROT_GROWSDOWN|PROT_GROWSUP);
 689         const bool rier = (current->personality & READ_IMPLIES_EXEC) &&
 690                                 (prot & PROT_READ);
 691         struct mmu_gather tlb;
 692         struct vma_iterator vmi;
 693
 694         start = untagged_addr(start);
 695
 696         prot &= ~(PROT_GROWSDOWN|PROT_GROWSUP);
 697         if (grows == (PROT_GROWSDOWN|PROT_GROWSUP)) /* can't be both */
 698                 return -EINVAL;
 699
 700         if (start & ~PAGE_MASK)
 701                 return -EINVAL;
 702         if (!len)
 703                 return 0;
 704         len = PAGE_ALIGN(len);
 705         end = start + len;
 706         if (end <= start)
 707                 return -ENOMEM;
 708         if (!arch_validate_prot(prot, start))
 709                 return -EINVAL;
 710
 711         reqprot = prot;
 712
 713         if (mmap_write_lock_killable(current->mm))
 714                 return -EINTR;
 715
 716         /*
 717          * If userspace did not allocate the pkey, do not let
 718          * them use it here.
 719          */
 720         error = -EINVAL;
 721         if ((pkey != -1) && !mm_pkey_is_allocated(current->mm, pkey))
 722                 goto out;
 723
 724         vma_iter_init(&vmi, current->mm, start);
 725         vma = vma_find(&vmi, end);
 726         error = -ENOMEM;
 727         if (!vma)
 728                 goto out;
 729
 730         if (unlikely(grows & PROT_GROWSDOWN)) {
 731                 if (vma->vm_start >= end)
 732                         goto out;
 733                 start = vma->vm_start;
 734                 error = -EINVAL;
 735                 if (!(vma->vm_flags & VM_GROWSDOWN))
 736                         goto out;
 737         } else {
 738                 if (vma->vm_start > start)
 739                         goto out;
 740                 if (unlikely(grows & PROT_GROWSUP)) {
 741                         end = vma->vm_end;
 742                         error = -EINVAL;
 743                         if (!(vma->vm_flags & VM_GROWSUP))
 744                                 goto out;
 745                 }
 746         }
 747
 748         /*
 749          * checking if memory is sealed.
 750          * can_modify_mm assumes we have acquired the lock on MM.
 751          */
 752         if (unlikely(!can_modify_mm(current->mm, start, end))) {
 753                 error = -EPERM;
 754                 goto out;
 755         }
 756
 757         prev = vma_prev(&vmi);
 758         if (start > vma->vm_start)
 759                 prev = vma;
 760
 761         tlb_gather_mmu(&tlb, current->mm);
 762         nstart = start;
 763         tmp = vma->vm_start;
 764         for_each_vma_range(vmi, vma, end) {
 765                 unsigned long mask_off_old_flags;
 766                 unsigned long newflags;
 767                 int new_vma_pkey;
 768
 769                 if (vma->vm_start != tmp) {
 770                         error = -ENOMEM;
 771                         break;
 772                 }
 773
 774                 /* Does the application expect PROT_READ to imply PROT_EXEC */
 775                 if (rier && (vma->vm_flags & VM_MAYEXEC))
 776                         prot |= PROT_EXEC;
 777
 778                 /*
 779                  * Each mprotect() call explicitly passes r/w/x permissions.
 780                  * If a permission is not passed to mprotect(), it must be
 781                  * cleared from the VMA.
 782                  */
 783                 mask_off_old_flags = VM_ACCESS_FLAGS | VM_FLAGS_CLEAR;
 784
 785                 new_vma_pkey = arch_override_mprotect_pkey(vma, prot, pkey);
 786                 newflags = calc_vm_prot_bits(prot, new_vma_pkey);
 787                 newflags |= (vma->vm_flags & ~mask_off_old_flags);
 788
 789                 /* newflags >> 4 shift VM_MAY% in place of VM_% */
 790                 if ((newflags & ~(newflags >> 4)) & VM_ACCESS_FLAGS) {
 791                         error = -EACCES;
 792                         break;
 793                 }
 794
 795                 if (map_deny_write_exec(vma, newflags)) {
 796                         error = -EACCES;
 797                         break;
 798                 }
 799
 800                 /* Allow architectures to sanity-check the new flags */
 801                 if (!arch_validate_flags(newflags)) {
 802                         error = -EINVAL;
 803                         break;
 804                 }
 805
 806                 error = security_file_mprotect(vma, reqprot, prot);
 807                 if (error)
 808                         break;
 809
 810                 tmp = vma->vm_end;
 811                 if (tmp > end)
 812                         tmp = end;
 813
 814                 if (vma->vm_ops && vma->vm_ops->mprotect) {
 815                         error = vma->vm_ops->mprotect(vma, nstart, tmp, newflags);
 816                         if (error)
 817                                 break;
 818                 }
 819
 820                 error = mprotect_fixup(&vmi, &tlb, vma, &prev, nstart, tmp, newflags);
 821                 if (error)
 822                         break;
 823
 824                 tmp = vma_iter_end(&vmi);
 825                 nstart = tmp;
 826                 prot = reqprot;
 827         }
 828         tlb_finish_mmu(&tlb);
 829
 830         if (!error && tmp < end)
 831                 error = -ENOMEM;
 832
 833 out:
 834         mmap_write_unlock(current->mm);
 835         return error;
 836 }
 837
 838 SYSCALL_DEFINE3(mprotect, unsigned long, start, size_t, len,
 839                 unsigned long, prot)
 840 {
 841         return do_mprotect_pkey(start, len, prot, -1);
 842 }
 843
 844 #ifdef CONFIG_ARCH_HAS_PKEYS
 845
 846 SYSCALL_DEFINE4(pkey_mprotect, unsigned long, start, size_t, len,
 847                 unsigned long, prot, int, pkey)
 848 {
 849         return do_mprotect_pkey(start, len, prot, pkey);
 850 }
 851
 852 SYSCALL_DEFINE2(pkey_alloc, unsigned long, flags, unsigned long, init_val)
 853 {
 854         int pkey;
 855         int ret;
 856
 857         /* No flags supported yet. */
 858         if (flags)
 859                 return -EINVAL;
 860         /* check for unsupported init values */
 861         if (init_val & ~PKEY_ACCESS_MASK)
 862                 return -EINVAL;
 863
 864         mmap_write_lock(current->mm);
 865         pkey = mm_pkey_alloc(current->mm);
 866
 867         ret = -ENOSPC;
 868         if (pkey == -1)
 869                 goto out;
 870
 871         ret = arch_set_user_pkey_access(current, pkey, init_val);
 872         if (ret) {
 873                 mm_pkey_free(current->mm, pkey);
 874                 goto out;
 875         }
 876         ret = pkey;
 877 out:
 878         mmap_write_unlock(current->mm);
 879         return ret;
 880 }
 881
 882 SYSCALL_DEFINE1(pkey_free, int, pkey)
 883 {
 884         int ret;
 885
 886         mmap_write_lock(current->mm);
 887         ret = mm_pkey_free(current->mm, pkey);
 888         mmap_write_unlock(current->mm);
 889
 890         /*
 891          * We could provide warnings or errors if any VMA still
 892          * has the pkey set here.
 893          */
 894         return ret;
 895 }
 896
 897 #endif /* CONFIG_ARCH_HAS_PKEYS */