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       <[email protected]>
   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 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         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_mkuffd_wp(ptent);
 182                         else if (uffd_wp_resolve)
 183                                 ptent = pte_clear_uffd_wp(ptent);
 184
 185                         /*
 186                          * In some writable, shared mappings, we might want
 187                          * to catch actual write access -- see
 188                          * vma_wants_writenotify().
 189                          *
 190                          * In all writable, private mappings, we have to
 191                          * properly handle COW.
 192                          *
 193                          * In both cases, we can sometimes still change PTEs
 194                          * writable and avoid the write-fault handler, for
 195                          * example, if a PTE is already dirty and no other
 196                          * COW or special handling is required.
 197                          */
 198                         if ((cp_flags & MM_CP_TRY_CHANGE_WRITABLE) &&
 199                             !pte_write(ptent) &&
 200                             can_change_pte_writable(vma, addr, ptent))
 201                                 ptent = pte_mkwrite(ptent);
 202
 203                         ptep_modify_prot_commit(vma, addr, pte, oldpte, ptent);
 204                         if (pte_needs_flush(oldpte, ptent))
 205                                 tlb_flush_pte_range(tlb, addr, PAGE_SIZE);
 206                         pages++;
 207                 } else if (is_swap_pte(oldpte)) {
 208                         swp_entry_t entry = pte_to_swp_entry(oldpte);
 209                         pte_t newpte;
 210
 211                         if (is_writable_migration_entry(entry)) {
 212                                 struct page *page = pfn_swap_entry_to_page(entry);
 213
 214                                 /*
 215                                  * A protection check is difficult so
 216                                  * just be safe and disable write
 217                                  */
 218                                 if (PageAnon(page))
 219                                         entry = make_readable_exclusive_migration_entry(
 220                                                              swp_offset(entry));
 221                                 else
 222                                         entry = make_readable_migration_entry(swp_offset(entry));
 223                                 newpte = swp_entry_to_pte(entry);
 224                                 if (pte_swp_soft_dirty(oldpte))
 225                                         newpte = pte_swp_mksoft_dirty(newpte);
 226                                 if (pte_swp_uffd_wp(oldpte))
 227                                         newpte = pte_swp_mkuffd_wp(newpte);
 228                         } else if (is_writable_device_private_entry(entry)) {
 229                                 /*
 230                                  * We do not preserve soft-dirtiness. See
 231                                  * copy_one_pte() for explanation.
 232                                  */
 233                                 entry = make_readable_device_private_entry(
 234                                                         swp_offset(entry));
 235                                 newpte = swp_entry_to_pte(entry);
 236                                 if (pte_swp_uffd_wp(oldpte))
 237                                         newpte = pte_swp_mkuffd_wp(newpte);
 238                         } else if (is_writable_device_exclusive_entry(entry)) {
 239                                 entry = make_readable_device_exclusive_entry(
 240                                                         swp_offset(entry));
 241                                 newpte = swp_entry_to_pte(entry);
 242                                 if (pte_swp_soft_dirty(oldpte))
 243                                         newpte = pte_swp_mksoft_dirty(newpte);
 244                                 if (pte_swp_uffd_wp(oldpte))
 245                                         newpte = pte_swp_mkuffd_wp(newpte);
 246                         } else if (is_pte_marker_entry(entry)) {
 247                                 /*
 248                                  * Ignore swapin errors unconditionally,
 249                                  * because any access should sigbus anyway.
 250                                  */
 251                                 if (is_swapin_error_entry(entry))
 252                                         continue;
 253                                 /*
 254                                  * If this is uffd-wp pte marker and we'd like
 255                                  * to unprotect it, drop it; the next page
 256                                  * fault will trigger without uffd trapping.
 257                                  */
 258                                 if (uffd_wp_resolve) {
 259                                         pte_clear(vma->vm_mm, addr, pte);
 260                                         pages++;
 261                                 }
 262                                 continue;
 263                         } else {
 264                                 newpte = oldpte;
 265                         }
 266
 267                         if (uffd_wp)
 268                                 newpte = pte_swp_mkuffd_wp(newpte);
 269                         else if (uffd_wp_resolve)
 270                                 newpte = pte_swp_clear_uffd_wp(newpte);
 271
 272                         if (!pte_same(oldpte, newpte)) {
 273                                 set_pte_at(vma->vm_mm, addr, pte, newpte);
 274                                 pages++;
 275                         }
 276                 } else {
 277                         /* It must be an none page, or what else?.. */
 278                         WARN_ON_ONCE(!pte_none(oldpte));
 279
 280                         /*
 281                          * Nobody plays with any none ptes besides
 282                          * userfaultfd when applying the protections.
 283                          */
 284                         if (likely(!uffd_wp))
 285                                 continue;
 286
 287                         if (userfaultfd_wp_use_markers(vma)) {
 288                                 /*
 289                                  * For file-backed mem, we need to be able to
 290                                  * wr-protect a none pte, because even if the
 291                                  * pte is none, the page/swap cache could
 292                                  * exist.  Doing that by install a marker.
 293                                  */
 294                                 set_pte_at(vma->vm_mm, addr, pte,
 295                                            make_pte_marker(PTE_MARKER_UFFD_WP));
 296                                 pages++;
 297                         }
 298                 }
 299         } while (pte++, addr += PAGE_SIZE, addr != end);
 300         arch_leave_lazy_mmu_mode();
 301         pte_unmap_unlock(pte - 1, ptl);
 302
 303         return pages;
 304 }
 305
 306 /*
 307  * Used when setting automatic NUMA hinting protection where it is
 308  * critical that a numa hinting PMD is not confused with a bad PMD.
 309  */
 310 static inline int pmd_none_or_clear_bad_unless_trans_huge(pmd_t *pmd)
 311 {
 312         pmd_t pmdval = pmdp_get_lockless(pmd);
 313
 314         /* See pmd_none_or_trans_huge_or_clear_bad for info on barrier */
 315 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 316         barrier();
 317 #endif
 318
 319         if (pmd_none(pmdval))
 320                 return 1;
 321         if (pmd_trans_huge(pmdval))
 322                 return 0;
 323         if (unlikely(pmd_bad(pmdval))) {
 324                 pmd_clear_bad(pmd);
 325                 return 1;
 326         }
 327
 328         return 0;
 329 }
 330
 331 /*
 332  * Return true if we want to split THPs into PTE mappings in change
 333  * protection procedure, false otherwise.
 334  */
 335 static inline bool
 336 pgtable_split_needed(struct vm_area_struct *vma, unsigned long cp_flags)
 337 {
 338         /*
 339          * pte markers only resides in pte level, if we need pte markers,
 340          * we need to split.  We cannot wr-protect shmem thp because file
 341          * thp is handled differently when split by erasing the pmd so far.
 342          */
 343         return (cp_flags & MM_CP_UFFD_WP) && !vma_is_anonymous(vma);
 344 }
 345
 346 /*
 347  * Return true if we want to populate pgtables in change protection
 348  * procedure, false otherwise
 349  */
 350 static inline bool
 351 pgtable_populate_needed(struct vm_area_struct *vma, unsigned long cp_flags)
 352 {
 353         /* If not within ioctl(UFFDIO_WRITEPROTECT), then don't bother */
 354         if (!(cp_flags & MM_CP_UFFD_WP))
 355                 return false;
 356
 357         /* Populate if the userfaultfd mode requires pte markers */
 358         return userfaultfd_wp_use_markers(vma);
 359 }
 360
 361 /*
 362  * Populate the pgtable underneath for whatever reason if requested.
 363  * When {pte|pmd|...}_alloc() failed we treat it the same way as pgtable
 364  * allocation failures during page faults by kicking OOM and returning
 365  * error.
 366  */
 367 #define  change_pmd_prepare(vma, pmd, cp_flags)                         \
 368         ({                                                              \
 369                 long err = 0;                                           \
 370                 if (unlikely(pgtable_populate_needed(vma, cp_flags))) { \
 371                         if (pte_alloc(vma->vm_mm, pmd))                 \
 372                                 err = -ENOMEM;                          \
 373                 }                                                       \
 374                 err;                                                    \
 375         })
 376
 377 /*
 378  * This is the general pud/p4d/pgd version of change_pmd_prepare(). We need to
 379  * have separate change_pmd_prepare() because pte_alloc() returns 0 on success,
 380  * while {pmd|pud|p4d}_alloc() returns the valid pointer on success.
 381  */
 382 #define  change_prepare(vma, high, low, addr, cp_flags)                 \
 383           ({                                                            \
 384                 long err = 0;                                           \
 385                 if (unlikely(pgtable_populate_needed(vma, cp_flags))) { \
 386                         low##_t *p = low##_alloc(vma->vm_mm, high, addr); \
 387                         if (p == NULL)                                  \
 388                                 err = -ENOMEM;                          \
 389                 }                                                       \
 390                 err;                                                    \
 391         })
 392
 393 static inline long change_pmd_range(struct mmu_gather *tlb,
 394                 struct vm_area_struct *vma, pud_t *pud, unsigned long addr,
 395                 unsigned long end, pgprot_t newprot, unsigned long cp_flags)
 396 {
 397         pmd_t *pmd;
 398         unsigned long next;
 399         long pages = 0;
 400         unsigned long nr_huge_updates = 0;
 401         struct mmu_notifier_range range;
 402
 403         range.start = 0;
 404
 405         pmd = pmd_offset(pud, addr);
 406         do {
 407                 long ret;
 408
 409                 next = pmd_addr_end(addr, end);
 410
 411                 ret = change_pmd_prepare(vma, pmd, cp_flags);
 412                 if (ret) {
 413                         pages = ret;
 414                         break;
 415                 }
 416                 /*
 417                  * Automatic NUMA balancing walks the tables with mmap_lock
 418                  * held for read. It's possible a parallel update to occur
 419                  * between pmd_trans_huge() and a pmd_none_or_clear_bad()
 420                  * check leading to a false positive and clearing.
 421                  * Hence, it's necessary to atomically read the PMD value
 422                  * for all the checks.
 423                  */
 424                 if (!is_swap_pmd(*pmd) && !pmd_devmap(*pmd) &&
 425                      pmd_none_or_clear_bad_unless_trans_huge(pmd))
 426                         goto next;
 427
 428                 /* invoke the mmu notifier if the pmd is populated */
 429                 if (!range.start) {
 430                         mmu_notifier_range_init(&range,
 431                                 MMU_NOTIFY_PROTECTION_VMA, 0,
 432                                 vma->vm_mm, addr, end);
 433                         mmu_notifier_invalidate_range_start(&range);
 434                 }
 435
 436                 if (is_swap_pmd(*pmd) || pmd_trans_huge(*pmd) || pmd_devmap(*pmd)) {
 437                         if ((next - addr != HPAGE_PMD_SIZE) ||
 438                             pgtable_split_needed(vma, cp_flags)) {
 439                                 __split_huge_pmd(vma, pmd, addr, false, NULL);
 440                                 /*
 441                                  * For file-backed, the pmd could have been
 442                                  * cleared; make sure pmd populated if
 443                                  * necessary, then fall-through to pte level.
 444                                  */
 445                                 ret = change_pmd_prepare(vma, pmd, cp_flags);
 446                                 if (ret) {
 447                                         pages = ret;
 448                                         break;
 449                                 }
 450                         } else {
 451                                 /*
 452                                  * change_huge_pmd() does not defer TLB flushes,
 453                                  * so no need to propagate the tlb argument.
 454                                  */
 455                                 int nr_ptes = change_huge_pmd(tlb, vma, pmd,
 456                                                 addr, newprot, cp_flags);
 457
 458                                 if (nr_ptes) {
 459                                         if (nr_ptes == HPAGE_PMD_NR) {
 460                                                 pages += HPAGE_PMD_NR;
 461                                                 nr_huge_updates++;
 462                                         }
 463
 464                                         /* huge pmd was handled */
 465                                         goto next;
 466                                 }
 467                         }
 468                         /* fall through, the trans huge pmd just split */
 469                 }
 470                 pages += change_pte_range(tlb, vma, pmd, addr, next,
 471                                           newprot, cp_flags);
 472 next:
 473                 cond_resched();
 474         } while (pmd++, addr = next, addr != end);
 475
 476         if (range.start)
 477                 mmu_notifier_invalidate_range_end(&range);
 478
 479         if (nr_huge_updates)
 480                 count_vm_numa_events(NUMA_HUGE_PTE_UPDATES, nr_huge_updates);
 481         return pages;
 482 }
 483
 484 static inline long change_pud_range(struct mmu_gather *tlb,
 485                 struct vm_area_struct *vma, p4d_t *p4d, unsigned long addr,
 486                 unsigned long end, pgprot_t newprot, unsigned long cp_flags)
 487 {
 488         pud_t *pud;
 489         unsigned long next;
 490         long pages = 0, ret;
 491
 492         pud = pud_offset(p4d, addr);
 493         do {
 494                 next = pud_addr_end(addr, end);
 495                 ret = change_prepare(vma, pud, pmd, addr, cp_flags);
 496                 if (ret)
 497                         return ret;
 498                 if (pud_none_or_clear_bad(pud))
 499                         continue;
 500                 pages += change_pmd_range(tlb, vma, pud, addr, next, newprot,
 501                                           cp_flags);
 502         } while (pud++, addr = next, addr != end);
 503
 504         return pages;
 505 }
 506
 507 static inline long change_p4d_range(struct mmu_gather *tlb,
 508                 struct vm_area_struct *vma, pgd_t *pgd, unsigned long addr,
 509                 unsigned long end, pgprot_t newprot, unsigned long cp_flags)
 510 {
 511         p4d_t *p4d;
 512         unsigned long next;
 513         long pages = 0, ret;
 514
 515         p4d = p4d_offset(pgd, addr);
 516         do {
 517                 next = p4d_addr_end(addr, end);
 518                 ret = change_prepare(vma, p4d, pud, addr, cp_flags);
 519                 if (ret)
 520                         return ret;
 521                 if (p4d_none_or_clear_bad(p4d))
 522                         continue;
 523                 pages += change_pud_range(tlb, vma, p4d, addr, next, newprot,
 524                                           cp_flags);
 525         } while (p4d++, addr = next, addr != end);
 526
 527         return pages;
 528 }
 529
 530 static long change_protection_range(struct mmu_gather *tlb,
 531                 struct vm_area_struct *vma, unsigned long addr,
 532                 unsigned long end, pgprot_t newprot, unsigned long cp_flags)
 533 {
 534         struct mm_struct *mm = vma->vm_mm;
 535         pgd_t *pgd;
 536         unsigned long next;
 537         long pages = 0, ret;
 538
 539         BUG_ON(addr >= end);
 540         pgd = pgd_offset(mm, addr);
 541         tlb_start_vma(tlb, vma);
 542         do {
 543                 next = pgd_addr_end(addr, end);
 544                 ret = change_prepare(vma, pgd, p4d, addr, cp_flags);
 545                 if (ret) {
 546                         pages = ret;
 547                         break;
 548                 }
 549                 if (pgd_none_or_clear_bad(pgd))
 550                         continue;
 551                 pages += change_p4d_range(tlb, vma, pgd, addr, next, newprot,
 552                                           cp_flags);
 553         } while (pgd++, addr = next, addr != end);
 554
 555         tlb_end_vma(tlb, vma);
 556
 557         return pages;
 558 }
 559
 560 long change_protection(struct mmu_gather *tlb,
 561                        struct vm_area_struct *vma, unsigned long start,
 562                        unsigned long end, unsigned long cp_flags)
 563 {
 564         pgprot_t newprot = vma->vm_page_prot;
 565         long pages;
 566
 567         BUG_ON((cp_flags & MM_CP_UFFD_WP_ALL) == MM_CP_UFFD_WP_ALL);
 568
 569 #ifdef CONFIG_NUMA_BALANCING
 570         /*
 571          * Ordinary protection updates (mprotect, uffd-wp, softdirty tracking)
 572          * are expected to reflect their requirements via VMA flags such that
 573          * vma_set_page_prot() will adjust vma->vm_page_prot accordingly.
 574          */
 575         if (cp_flags & MM_CP_PROT_NUMA)
 576                 newprot = PAGE_NONE;
 577 #else
 578         WARN_ON_ONCE(cp_flags & MM_CP_PROT_NUMA);
 579 #endif
 580
 581         if (is_vm_hugetlb_page(vma))
 582                 pages = hugetlb_change_protection(vma, start, end, newprot,
 583                                                   cp_flags);
 584         else
 585                 pages = change_protection_range(tlb, vma, start, end, newprot,
 586                                                 cp_flags);
 587
 588         return pages;
 589 }
 590
 591 static int prot_none_pte_entry(pte_t *pte, unsigned long addr,
 592                                unsigned long next, struct mm_walk *walk)
 593 {
 594         return pfn_modify_allowed(pte_pfn(*pte), *(pgprot_t *)(walk->private)) ?
 595                 0 : -EACCES;
 596 }
 597
 598 static int prot_none_hugetlb_entry(pte_t *pte, unsigned long hmask,
 599                                    unsigned long addr, unsigned long next,
 600                                    struct mm_walk *walk)
 601 {
 602         return pfn_modify_allowed(pte_pfn(*pte), *(pgprot_t *)(walk->private)) ?
 603                 0 : -EACCES;
 604 }
 605
 606 static int prot_none_test(unsigned long addr, unsigned long next,
 607                           struct mm_walk *walk)
 608 {
 609         return 0;
 610 }
 611
 612 static const struct mm_walk_ops prot_none_walk_ops = {
 613         .pte_entry              = prot_none_pte_entry,
 614         .hugetlb_entry          = prot_none_hugetlb_entry,
 615         .test_walk              = prot_none_test,
 616 };
 617
 618 int
 619 mprotect_fixup(struct vma_iterator *vmi, struct mmu_gather *tlb,
 620                struct vm_area_struct *vma, struct vm_area_struct **pprev,
 621                unsigned long start, unsigned long end, unsigned long newflags)
 622 {
 623         struct mm_struct *mm = vma->vm_mm;
 624         unsigned long oldflags = vma->vm_flags;
 625         long nrpages = (end - start) >> PAGE_SHIFT;
 626         unsigned int mm_cp_flags = 0;
 627         unsigned long charged = 0;
 628         pgoff_t pgoff;
 629         int error;
 630
 631         if (newflags == oldflags) {
 632                 *pprev = vma;
 633                 return 0;
 634         }
 635
 636         /*
 637          * Do PROT_NONE PFN permission checks here when we can still
 638          * bail out without undoing a lot of state. This is a rather
 639          * uncommon case, so doesn't need to be very optimized.
 640          */
 641         if (arch_has_pfn_modify_check() &&
 642             (vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
 643             (newflags & VM_ACCESS_FLAGS) == 0) {
 644                 pgprot_t new_pgprot = vm_get_page_prot(newflags);
 645
 646                 error = walk_page_range(current->mm, start, end,
 647                                 &prot_none_walk_ops, &new_pgprot);
 648                 if (error)
 649                         return error;
 650         }
 651
 652         /*
 653          * If we make a private mapping writable we increase our commit;
 654          * but (without finer accounting) cannot reduce our commit if we
 655          * make it unwritable again. hugetlb mapping were accounted for
 656          * even if read-only so there is no need to account for them here
 657          */
 658         if (newflags & VM_WRITE) {
 659                 /* Check space limits when area turns into data. */
 660                 if (!may_expand_vm(mm, newflags, nrpages) &&
 661                                 may_expand_vm(mm, oldflags, nrpages))
 662                         return -ENOMEM;
 663                 if (!(oldflags & (VM_ACCOUNT|VM_WRITE|VM_HUGETLB|
 664                                                 VM_SHARED|VM_NORESERVE))) {
 665                         charged = nrpages;
 666                         if (security_vm_enough_memory_mm(mm, charged))
 667                                 return -ENOMEM;
 668                         newflags |= VM_ACCOUNT;
 669                 }
 670         }
 671
 672         /*
 673          * First try to merge with previous and/or next vma.
 674          */
 675         pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
 676         *pprev = vma_merge(vmi, mm, *pprev, start, end, newflags,
 677                            vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma),
 678                            vma->vm_userfaultfd_ctx, anon_vma_name(vma));
 679         if (*pprev) {
 680                 vma = *pprev;
 681                 VM_WARN_ON((vma->vm_flags ^ newflags) & ~VM_SOFTDIRTY);
 682                 goto success;
 683         }
 684
 685         *pprev = vma;
 686
 687         if (start != vma->vm_start) {
 688                 error = split_vma(vmi, vma, start, 1);
 689                 if (error)
 690                         goto fail;
 691         }
 692
 693         if (end != vma->vm_end) {
 694                 error = split_vma(vmi, vma, end, 0);
 695                 if (error)
 696                         goto fail;
 697         }
 698
 699 success:
 700         /*
 701          * vm_flags and vm_page_prot are protected by the mmap_lock
 702          * held in write mode.
 703          */
 704         vm_flags_reset(vma, newflags);
 705         if (vma_wants_manual_pte_write_upgrade(vma))
 706                 mm_cp_flags |= MM_CP_TRY_CHANGE_WRITABLE;
 707         vma_set_page_prot(vma);
 708
 709         change_protection(tlb, vma, start, end, mm_cp_flags);
 710
 711         /*
 712          * Private VM_LOCKED VMA becoming writable: trigger COW to avoid major
 713          * fault on access.
 714          */
 715         if ((oldflags & (VM_WRITE | VM_SHARED | VM_LOCKED)) == VM_LOCKED &&
 716                         (newflags & VM_WRITE)) {
 717                 populate_vma_page_range(vma, start, end, NULL);
 718         }
 719
 720         vm_stat_account(mm, oldflags, -nrpages);
 721         vm_stat_account(mm, newflags, nrpages);
 722         perf_event_mmap(vma);
 723         return 0;
 724
 725 fail:
 726         vm_unacct_memory(charged);
 727         return error;
 728 }
 729
 730 /*
 731  * pkey==-1 when doing a legacy mprotect()
 732  */
 733 static int do_mprotect_pkey(unsigned long start, size_t len,
 734                 unsigned long prot, int pkey)
 735 {
 736         unsigned long nstart, end, tmp, reqprot;
 737         struct vm_area_struct *vma, *prev;
 738         int error;
 739         const int grows = prot & (PROT_GROWSDOWN|PROT_GROWSUP);
 740         const bool rier = (current->personality & READ_IMPLIES_EXEC) &&
 741                                 (prot & PROT_READ);
 742         struct mmu_gather tlb;
 743         struct vma_iterator vmi;
 744
 745         start = untagged_addr(start);
 746
 747         prot &= ~(PROT_GROWSDOWN|PROT_GROWSUP);
 748         if (grows == (PROT_GROWSDOWN|PROT_GROWSUP)) /* can't be both */
 749                 return -EINVAL;
 750
 751         if (start & ~PAGE_MASK)
 752                 return -EINVAL;
 753         if (!len)
 754                 return 0;
 755         len = PAGE_ALIGN(len);
 756         end = start + len;
 757         if (end <= start)
 758                 return -ENOMEM;
 759         if (!arch_validate_prot(prot, start))
 760                 return -EINVAL;
 761
 762         reqprot = prot;
 763
 764         if (mmap_write_lock_killable(current->mm))
 765                 return -EINTR;
 766
 767         /*
 768          * If userspace did not allocate the pkey, do not let
 769          * them use it here.
 770          */
 771         error = -EINVAL;
 772         if ((pkey != -1) && !mm_pkey_is_allocated(current->mm, pkey))
 773                 goto out;
 774
 775         vma_iter_init(&vmi, current->mm, start);
 776         vma = vma_find(&vmi, end);
 777         error = -ENOMEM;
 778         if (!vma)
 779                 goto out;
 780
 781         if (unlikely(grows & PROT_GROWSDOWN)) {
 782                 if (vma->vm_start >= end)
 783                         goto out;
 784                 start = vma->vm_start;
 785                 error = -EINVAL;
 786                 if (!(vma->vm_flags & VM_GROWSDOWN))
 787                         goto out;
 788         } else {
 789                 if (vma->vm_start > start)
 790                         goto out;
 791                 if (unlikely(grows & PROT_GROWSUP)) {
 792                         end = vma->vm_end;
 793                         error = -EINVAL;
 794                         if (!(vma->vm_flags & VM_GROWSUP))
 795                                 goto out;
 796                 }
 797         }
 798
 799         prev = vma_prev(&vmi);
 800         if (start > vma->vm_start)
 801                 prev = vma;
 802
 803         tlb_gather_mmu(&tlb, current->mm);
 804         nstart = start;
 805         tmp = vma->vm_start;
 806         for_each_vma_range(vmi, vma, end) {
 807                 unsigned long mask_off_old_flags;
 808                 unsigned long newflags;
 809                 int new_vma_pkey;
 810
 811                 if (vma->vm_start != tmp) {
 812                         error = -ENOMEM;
 813                         break;
 814                 }
 815
 816                 /* Does the application expect PROT_READ to imply PROT_EXEC */
 817                 if (rier && (vma->vm_flags & VM_MAYEXEC))
 818                         prot |= PROT_EXEC;
 819
 820                 /*
 821                  * Each mprotect() call explicitly passes r/w/x permissions.
 822                  * If a permission is not passed to mprotect(), it must be
 823                  * cleared from the VMA.
 824                  */
 825                 mask_off_old_flags = VM_ACCESS_FLAGS | VM_FLAGS_CLEAR;
 826
 827                 new_vma_pkey = arch_override_mprotect_pkey(vma, prot, pkey);
 828                 newflags = calc_vm_prot_bits(prot, new_vma_pkey);
 829                 newflags |= (vma->vm_flags & ~mask_off_old_flags);
 830
 831                 /* newflags >> 4 shift VM_MAY% in place of VM_% */
 832                 if ((newflags & ~(newflags >> 4)) & VM_ACCESS_FLAGS) {
 833                         error = -EACCES;
 834                         break;
 835                 }
 836
 837                 if (map_deny_write_exec(vma, newflags)) {
 838                         error = -EACCES;
 839                         break;
 840                 }
 841
 842                 /* Allow architectures to sanity-check the new flags */
 843                 if (!arch_validate_flags(newflags)) {
 844                         error = -EINVAL;
 845                         break;
 846                 }
 847
 848                 error = security_file_mprotect(vma, reqprot, prot);
 849                 if (error)
 850                         break;
 851
 852                 tmp = vma->vm_end;
 853                 if (tmp > end)
 854                         tmp = end;
 855
 856                 if (vma->vm_ops && vma->vm_ops->mprotect) {
 857                         error = vma->vm_ops->mprotect(vma, nstart, tmp, newflags);
 858                         if (error)
 859                                 break;
 860                 }
 861
 862                 error = mprotect_fixup(&vmi, &tlb, vma, &prev, nstart, tmp, newflags);
 863                 if (error)
 864                         break;
 865
 866                 tmp = vma_iter_end(&vmi);
 867                 nstart = tmp;
 868                 prot = reqprot;
 869         }
 870         tlb_finish_mmu(&tlb);
 871
 872         if (vma_iter_end(&vmi) < end)
 873                 error = -ENOMEM;
 874
 875 out:
 876         mmap_write_unlock(current->mm);
 877         return error;
 878 }
 879
 880 SYSCALL_DEFINE3(mprotect, unsigned long, start, size_t, len,
 881                 unsigned long, prot)
 882 {
 883         return do_mprotect_pkey(start, len, prot, -1);
 884 }
 885
 886 #ifdef CONFIG_ARCH_HAS_PKEYS
 887
 888 SYSCALL_DEFINE4(pkey_mprotect, unsigned long, start, size_t, len,
 889                 unsigned long, prot, int, pkey)
 890 {
 891         return do_mprotect_pkey(start, len, prot, pkey);
 892 }
 893
 894 SYSCALL_DEFINE2(pkey_alloc, unsigned long, flags, unsigned long, init_val)
 895 {
 896         int pkey;
 897         int ret;
 898
 899         /* No flags supported yet. */
 900         if (flags)
 901                 return -EINVAL;
 902         /* check for unsupported init values */
 903         if (init_val & ~PKEY_ACCESS_MASK)
 904                 return -EINVAL;
 905
 906         mmap_write_lock(current->mm);
 907         pkey = mm_pkey_alloc(current->mm);
 908
 909         ret = -ENOSPC;
 910         if (pkey == -1)
 911                 goto out;
 912
 913         ret = arch_set_user_pkey_access(current, pkey, init_val);
 914         if (ret) {
 915                 mm_pkey_free(current->mm, pkey);
 916                 goto out;
 917         }
 918         ret = pkey;
 919 out:
 920         mmap_write_unlock(current->mm);
 921         return ret;
 922 }
 923
 924 SYSCALL_DEFINE1(pkey_free, int, pkey)
 925 {
 926         int ret;
 927
 928         mmap_write_lock(current->mm);
 929         ret = mm_pkey_free(current->mm, pkey);
 930         mmap_write_unlock(current->mm);
 931
 932         /*
 933          * We could provide warnings or errors if any VMA still
 934          * has the pkey set here.
 935          */
 936         return ret;
 937 }
 938
 939 #endif /* CONFIG_ARCH_HAS_PKEYS */