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/mm.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 <asm/pgtable.h>
  32 #include <asm/cacheflush.h>
  33 #include <asm/mmu_context.h>
  34 #include <asm/tlbflush.h>
  35
  36 #include "internal.h"
  37
  38 static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
  39                 unsigned long addr, unsigned long end, pgprot_t newprot,
  40                 int dirty_accountable, int prot_numa)
  41 {
  42         struct mm_struct *mm = vma->vm_mm;
  43         pte_t *pte, oldpte;
  44         spinlock_t *ptl;
  45         unsigned long pages = 0;
  46         int target_node = NUMA_NO_NODE;
  47
  48         /*
  49          * Can be called with only the mmap_sem for reading by
  50          * prot_numa so we must check the pmd isn't constantly
  51          * changing from under us from pmd_none to pmd_trans_huge
  52          * and/or the other way around.
  53          */
  54         if (pmd_trans_unstable(pmd))
  55                 return 0;
  56
  57         /*
  58          * The pmd points to a regular pte so the pmd can't change
  59          * from under us even if the mmap_sem is only hold for
  60          * reading.
  61          */
  62         pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
  63
  64         /* Get target node for single threaded private VMAs */
  65         if (prot_numa && !(vma->vm_flags & VM_SHARED) &&
  66             atomic_read(&vma->vm_mm->mm_users) == 1)
  67                 target_node = numa_node_id();
  68
  69         flush_tlb_batched_pending(vma->vm_mm);
  70         arch_enter_lazy_mmu_mode();
  71         do {
  72                 oldpte = *pte;
  73                 if (pte_present(oldpte)) {
  74                         pte_t ptent;
  75                         bool preserve_write = prot_numa && pte_write(oldpte);
  76
  77                         /*
  78                          * Avoid trapping faults against the zero or KSM
  79                          * pages. See similar comment in change_huge_pmd.
  80                          */
  81                         if (prot_numa) {
  82                                 struct page *page;
  83
  84                                 page = vm_normal_page(vma, addr, oldpte);
  85                                 if (!page || PageKsm(page))
  86                                         continue;
  87
  88                                 /* Also skip shared copy-on-write pages */
  89                                 if (is_cow_mapping(vma->vm_flags) &&
  90                                     page_mapcount(page) != 1)
  91                                         continue;
  92
  93                                 /*
  94                                  * While migration can move some dirty pages,
  95                                  * it cannot move them all from MIGRATE_ASYNC
  96                                  * context.
  97                                  */
  98                                 if (page_is_file_cache(page) && PageDirty(page))
  99                                         continue;
 100
 101                                 /* Avoid TLB flush if possible */
 102                                 if (pte_protnone(oldpte))
 103                                         continue;
 104
 105                                 /*
 106                                  * Don't mess with PTEs if page is already on the node
 107                                  * a single-threaded process is running on.
 108                                  */
 109                                 if (target_node == page_to_nid(page))
 110                                         continue;
 111                         }
 112
 113                         ptent = ptep_modify_prot_start(mm, addr, pte);
 114                         ptent = pte_modify(ptent, newprot);
 115                         if (preserve_write)
 116                                 ptent = pte_mk_savedwrite(ptent);
 117
 118                         /* Avoid taking write faults for known dirty pages */
 119                         if (dirty_accountable && pte_dirty(ptent) &&
 120                                         (pte_soft_dirty(ptent) ||
 121                                          !(vma->vm_flags & VM_SOFTDIRTY))) {
 122                                 ptent = pte_mkwrite(ptent);
 123                         }
 124                         ptep_modify_prot_commit(mm, addr, pte, ptent);
 125                         pages++;
 126                 } else if (IS_ENABLED(CONFIG_MIGRATION)) {
 127                         swp_entry_t entry = pte_to_swp_entry(oldpte);
 128
 129                         if (is_write_migration_entry(entry)) {
 130                                 pte_t newpte;
 131                                 /*
 132                                  * A protection check is difficult so
 133                                  * just be safe and disable write
 134                                  */
 135                                 make_migration_entry_read(&entry);
 136                                 newpte = swp_entry_to_pte(entry);
 137                                 if (pte_swp_soft_dirty(oldpte))
 138                                         newpte = pte_swp_mksoft_dirty(newpte);
 139                                 set_pte_at(mm, addr, pte, newpte);
 140
 141                                 pages++;
 142                         }
 143
 144                         if (is_write_device_private_entry(entry)) {
 145                                 pte_t newpte;
 146
 147                                 /*
 148                                  * We do not preserve soft-dirtiness. See
 149                                  * copy_one_pte() for explanation.
 150                                  */
 151                                 make_device_private_entry_read(&entry);
 152                                 newpte = swp_entry_to_pte(entry);
 153                                 set_pte_at(mm, addr, pte, newpte);
 154
 155                                 pages++;
 156                         }
 157                 }
 158         } while (pte++, addr += PAGE_SIZE, addr != end);
 159         arch_leave_lazy_mmu_mode();
 160         pte_unmap_unlock(pte - 1, ptl);
 161
 162         return pages;
 163 }
 164
 165 /*
 166  * Used when setting automatic NUMA hinting protection where it is
 167  * critical that a numa hinting PMD is not confused with a bad PMD.
 168  */
 169 static inline int pmd_none_or_clear_bad_unless_trans_huge(pmd_t *pmd)
 170 {
 171         pmd_t pmdval = pmd_read_atomic(pmd);
 172
 173         /* See pmd_none_or_trans_huge_or_clear_bad for info on barrier */
 174 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 175         barrier();
 176 #endif
 177
 178         if (pmd_none(pmdval))
 179                 return 1;
 180         if (pmd_trans_huge(pmdval))
 181                 return 0;
 182         if (unlikely(pmd_bad(pmdval))) {
 183                 pmd_clear_bad(pmd);
 184                 return 1;
 185         }
 186
 187         return 0;
 188 }
 189
 190 static inline unsigned long change_pmd_range(struct vm_area_struct *vma,
 191                 pud_t *pud, unsigned long addr, unsigned long end,
 192                 pgprot_t newprot, int dirty_accountable, int prot_numa)
 193 {
 194         pmd_t *pmd;
 195         struct mm_struct *mm = vma->vm_mm;
 196         unsigned long next;
 197         unsigned long pages = 0;
 198         unsigned long nr_huge_updates = 0;
 199         unsigned long mni_start = 0;
 200
 201         pmd = pmd_offset(pud, addr);
 202         do {
 203                 unsigned long this_pages;
 204
 205                 next = pmd_addr_end(addr, end);
 206
 207                 /*
 208                  * Automatic NUMA balancing walks the tables with mmap_sem
 209                  * held for read. It's possible a parallel update to occur
 210                  * between pmd_trans_huge() and a pmd_none_or_clear_bad()
 211                  * check leading to a false positive and clearing.
 212                  * Hence, it's necessary to atomically read the PMD value
 213                  * for all the checks.
 214                  */
 215                 if (!is_swap_pmd(*pmd) && !pmd_devmap(*pmd) &&
 216                      pmd_none_or_clear_bad_unless_trans_huge(pmd))
 217                         goto next;
 218
 219                 /* invoke the mmu notifier if the pmd is populated */
 220                 if (!mni_start) {
 221                         mni_start = addr;
 222                         mmu_notifier_invalidate_range_start(mm, mni_start, end);
 223                 }
 224
 225                 if (is_swap_pmd(*pmd) || pmd_trans_huge(*pmd) || pmd_devmap(*pmd)) {
 226                         if (next - addr != HPAGE_PMD_SIZE) {
 227                                 __split_huge_pmd(vma, pmd, addr, false, NULL);
 228                         } else {
 229                                 int nr_ptes = change_huge_pmd(vma, pmd, addr,
 230                                                 newprot, prot_numa);
 231
 232                                 if (nr_ptes) {
 233                                         if (nr_ptes == HPAGE_PMD_NR) {
 234                                                 pages += HPAGE_PMD_NR;
 235                                                 nr_huge_updates++;
 236                                         }
 237
 238                                         /* huge pmd was handled */
 239                                         goto next;
 240                                 }
 241                         }
 242                         /* fall through, the trans huge pmd just split */
 243                 }
 244                 this_pages = change_pte_range(vma, pmd, addr, next, newprot,
 245                                  dirty_accountable, prot_numa);
 246                 pages += this_pages;
 247 next:
 248                 cond_resched();
 249         } while (pmd++, addr = next, addr != end);
 250
 251         if (mni_start)
 252                 mmu_notifier_invalidate_range_end(mm, mni_start, end);
 253
 254         if (nr_huge_updates)
 255                 count_vm_numa_events(NUMA_HUGE_PTE_UPDATES, nr_huge_updates);
 256         return pages;
 257 }
 258
 259 static inline unsigned long change_pud_range(struct vm_area_struct *vma,
 260                 p4d_t *p4d, unsigned long addr, unsigned long end,
 261                 pgprot_t newprot, int dirty_accountable, int prot_numa)
 262 {
 263         pud_t *pud;
 264         unsigned long next;
 265         unsigned long pages = 0;
 266
 267         pud = pud_offset(p4d, addr);
 268         do {
 269                 next = pud_addr_end(addr, end);
 270                 if (pud_none_or_clear_bad(pud))
 271                         continue;
 272                 pages += change_pmd_range(vma, pud, addr, next, newprot,
 273                                  dirty_accountable, prot_numa);
 274         } while (pud++, addr = next, addr != end);
 275
 276         return pages;
 277 }
 278
 279 static inline unsigned long change_p4d_range(struct vm_area_struct *vma,
 280                 pgd_t *pgd, unsigned long addr, unsigned long end,
 281                 pgprot_t newprot, int dirty_accountable, int prot_numa)
 282 {
 283         p4d_t *p4d;
 284         unsigned long next;
 285         unsigned long pages = 0;
 286
 287         p4d = p4d_offset(pgd, addr);
 288         do {
 289                 next = p4d_addr_end(addr, end);
 290                 if (p4d_none_or_clear_bad(p4d))
 291                         continue;
 292                 pages += change_pud_range(vma, p4d, addr, next, newprot,
 293                                  dirty_accountable, prot_numa);
 294         } while (p4d++, addr = next, addr != end);
 295
 296         return pages;
 297 }
 298
 299 static unsigned long change_protection_range(struct vm_area_struct *vma,
 300                 unsigned long addr, unsigned long end, pgprot_t newprot,
 301                 int dirty_accountable, int prot_numa)
 302 {
 303         struct mm_struct *mm = vma->vm_mm;
 304         pgd_t *pgd;
 305         unsigned long next;
 306         unsigned long start = addr;
 307         unsigned long pages = 0;
 308
 309         BUG_ON(addr >= end);
 310         pgd = pgd_offset(mm, addr);
 311         flush_cache_range(vma, addr, end);
 312         inc_tlb_flush_pending(mm);
 313         do {
 314                 next = pgd_addr_end(addr, end);
 315                 if (pgd_none_or_clear_bad(pgd))
 316                         continue;
 317                 pages += change_p4d_range(vma, pgd, addr, next, newprot,
 318                                  dirty_accountable, prot_numa);
 319         } while (pgd++, addr = next, addr != end);
 320
 321         /* Only flush the TLB if we actually modified any entries: */
 322         if (pages)
 323                 flush_tlb_range(vma, start, end);
 324         dec_tlb_flush_pending(mm);
 325
 326         return pages;
 327 }
 328
 329 unsigned long change_protection(struct vm_area_struct *vma, unsigned long start,
 330                        unsigned long end, pgprot_t newprot,
 331                        int dirty_accountable, int prot_numa)
 332 {
 333         unsigned long pages;
 334
 335         if (is_vm_hugetlb_page(vma))
 336                 pages = hugetlb_change_protection(vma, start, end, newprot);
 337         else
 338                 pages = change_protection_range(vma, start, end, newprot, dirty_accountable, prot_numa);
 339
 340         return pages;
 341 }
 342
 343 static int prot_none_pte_entry(pte_t *pte, unsigned long addr,
 344                                unsigned long next, struct mm_walk *walk)
 345 {
 346         return pfn_modify_allowed(pte_pfn(*pte), *(pgprot_t *)(walk->private)) ?
 347                 0 : -EACCES;
 348 }
 349
 350 static int prot_none_hugetlb_entry(pte_t *pte, unsigned long hmask,
 351                                    unsigned long addr, unsigned long next,
 352                                    struct mm_walk *walk)
 353 {
 354         return pfn_modify_allowed(pte_pfn(*pte), *(pgprot_t *)(walk->private)) ?
 355                 0 : -EACCES;
 356 }
 357
 358 static int prot_none_test(unsigned long addr, unsigned long next,
 359                           struct mm_walk *walk)
 360 {
 361         return 0;
 362 }
 363
 364 static int prot_none_walk(struct vm_area_struct *vma, unsigned long start,
 365                            unsigned long end, unsigned long newflags)
 366 {
 367         pgprot_t new_pgprot = vm_get_page_prot(newflags);
 368         struct mm_walk prot_none_walk = {
 369                 .pte_entry = prot_none_pte_entry,
 370                 .hugetlb_entry = prot_none_hugetlb_entry,
 371                 .test_walk = prot_none_test,
 372                 .mm = current->mm,
 373                 .private = &new_pgprot,
 374         };
 375
 376         return walk_page_range(start, end, &prot_none_walk);
 377 }
 378
 379 int
 380 mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev,
 381         unsigned long start, unsigned long end, unsigned long newflags)
 382 {
 383         struct mm_struct *mm = vma->vm_mm;
 384         unsigned long oldflags = vma->vm_flags;
 385         long nrpages = (end - start) >> PAGE_SHIFT;
 386         unsigned long charged = 0;
 387         pgoff_t pgoff;
 388         int error;
 389         int dirty_accountable = 0;
 390
 391         if (newflags == oldflags) {
 392                 *pprev = vma;
 393                 return 0;
 394         }
 395
 396         /*
 397          * Do PROT_NONE PFN permission checks here when we can still
 398          * bail out without undoing a lot of state. This is a rather
 399          * uncommon case, so doesn't need to be very optimized.
 400          */
 401         if (arch_has_pfn_modify_check() &&
 402             (vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
 403             (newflags & (VM_READ|VM_WRITE|VM_EXEC)) == 0) {
 404                 error = prot_none_walk(vma, start, end, newflags);
 405                 if (error)
 406                         return error;
 407         }
 408
 409         /*
 410          * If we make a private mapping writable we increase our commit;
 411          * but (without finer accounting) cannot reduce our commit if we
 412          * make it unwritable again. hugetlb mapping were accounted for
 413          * even if read-only so there is no need to account for them here
 414          */
 415         if (newflags & VM_WRITE) {
 416                 /* Check space limits when area turns into data. */
 417                 if (!may_expand_vm(mm, newflags, nrpages) &&
 418                                 may_expand_vm(mm, oldflags, nrpages))
 419                         return -ENOMEM;
 420                 if (!(oldflags & (VM_ACCOUNT|VM_WRITE|VM_HUGETLB|
 421                                                 VM_SHARED|VM_NORESERVE))) {
 422                         charged = nrpages;
 423                         if (security_vm_enough_memory_mm(mm, charged))
 424                                 return -ENOMEM;
 425                         newflags |= VM_ACCOUNT;
 426                 }
 427         }
 428
 429         /*
 430          * First try to merge with previous and/or next vma.
 431          */
 432         pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
 433         *pprev = vma_merge(mm, *pprev, start, end, newflags,
 434                            vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma),
 435                            vma->vm_userfaultfd_ctx);
 436         if (*pprev) {
 437                 vma = *pprev;
 438                 VM_WARN_ON((vma->vm_flags ^ newflags) & ~VM_SOFTDIRTY);
 439                 goto success;
 440         }
 441
 442         *pprev = vma;
 443
 444         if (start != vma->vm_start) {
 445                 error = split_vma(mm, vma, start, 1);
 446                 if (error)
 447                         goto fail;
 448         }
 449
 450         if (end != vma->vm_end) {
 451                 error = split_vma(mm, vma, end, 0);
 452                 if (error)
 453                         goto fail;
 454         }
 455
 456 success:
 457         /*
 458          * vm_flags and vm_page_prot are protected by the mmap_sem
 459          * held in write mode.
 460          */
 461         vma->vm_flags = newflags;
 462         dirty_accountable = vma_wants_writenotify(vma, vma->vm_page_prot);
 463         vma_set_page_prot(vma);
 464
 465         change_protection(vma, start, end, vma->vm_page_prot,
 466                           dirty_accountable, 0);
 467
 468         /*
 469          * Private VM_LOCKED VMA becoming writable: trigger COW to avoid major
 470          * fault on access.
 471          */
 472         if ((oldflags & (VM_WRITE | VM_SHARED | VM_LOCKED)) == VM_LOCKED &&
 473                         (newflags & VM_WRITE)) {
 474                 populate_vma_page_range(vma, start, end, NULL);
 475         }
 476
 477         vm_stat_account(mm, oldflags, -nrpages);
 478         vm_stat_account(mm, newflags, nrpages);
 479         perf_event_mmap(vma);
 480         return 0;
 481
 482 fail:
 483         vm_unacct_memory(charged);
 484         return error;
 485 }
 486
 487 /*
 488  * pkey==-1 when doing a legacy mprotect()
 489  */
 490 static int do_mprotect_pkey(unsigned long start, size_t len,
 491                 unsigned long prot, int pkey)
 492 {
 493         unsigned long nstart, end, tmp, reqprot;
 494         struct vm_area_struct *vma, *prev;
 495         int error = -EINVAL;
 496         const int grows = prot & (PROT_GROWSDOWN|PROT_GROWSUP);
 497         const bool rier = (current->personality & READ_IMPLIES_EXEC) &&
 498                                 (prot & PROT_READ);
 499
 500         prot &= ~(PROT_GROWSDOWN|PROT_GROWSUP);
 501         if (grows == (PROT_GROWSDOWN|PROT_GROWSUP)) /* can't be both */
 502                 return -EINVAL;
 503
 504         if (start & ~PAGE_MASK)
 505                 return -EINVAL;
 506         if (!len)
 507                 return 0;
 508         len = PAGE_ALIGN(len);
 509         end = start + len;
 510         if (end <= start)
 511                 return -ENOMEM;
 512         if (!arch_validate_prot(prot, start))
 513                 return -EINVAL;
 514
 515         reqprot = prot;
 516
 517         if (down_write_killable(&current->mm->mmap_sem))
 518                 return -EINTR;
 519
 520         /*
 521          * If userspace did not allocate the pkey, do not let
 522          * them use it here.
 523          */
 524         error = -EINVAL;
 525         if ((pkey != -1) && !mm_pkey_is_allocated(current->mm, pkey))
 526                 goto out;
 527
 528         vma = find_vma(current->mm, start);
 529         error = -ENOMEM;
 530         if (!vma)
 531                 goto out;
 532         prev = vma->vm_prev;
 533         if (unlikely(grows & PROT_GROWSDOWN)) {
 534                 if (vma->vm_start >= end)
 535                         goto out;
 536                 start = vma->vm_start;
 537                 error = -EINVAL;
 538                 if (!(vma->vm_flags & VM_GROWSDOWN))
 539                         goto out;
 540         } else {
 541                 if (vma->vm_start > start)
 542                         goto out;
 543                 if (unlikely(grows & PROT_GROWSUP)) {
 544                         end = vma->vm_end;
 545                         error = -EINVAL;
 546                         if (!(vma->vm_flags & VM_GROWSUP))
 547                                 goto out;
 548                 }
 549         }
 550         if (start > vma->vm_start)
 551                 prev = vma;
 552
 553         for (nstart = start ; ; ) {
 554                 unsigned long mask_off_old_flags;
 555                 unsigned long newflags;
 556                 int new_vma_pkey;
 557
 558                 /* Here we know that vma->vm_start <= nstart < vma->vm_end. */
 559
 560                 /* Does the application expect PROT_READ to imply PROT_EXEC */
 561                 if (rier && (vma->vm_flags & VM_MAYEXEC))
 562                         prot |= PROT_EXEC;
 563
 564                 /*
 565                  * Each mprotect() call explicitly passes r/w/x permissions.
 566                  * If a permission is not passed to mprotect(), it must be
 567                  * cleared from the VMA.
 568                  */
 569                 mask_off_old_flags = VM_READ | VM_WRITE | VM_EXEC |
 570                                         VM_FLAGS_CLEAR;
 571
 572                 new_vma_pkey = arch_override_mprotect_pkey(vma, prot, pkey);
 573                 newflags = calc_vm_prot_bits(prot, new_vma_pkey);
 574                 newflags |= (vma->vm_flags & ~mask_off_old_flags);
 575
 576                 /* newflags >> 4 shift VM_MAY% in place of VM_% */
 577                 if ((newflags & ~(newflags >> 4)) & (VM_READ | VM_WRITE | VM_EXEC)) {
 578                         error = -EACCES;
 579                         goto out;
 580                 }
 581
 582                 error = security_file_mprotect(vma, reqprot, prot);
 583                 if (error)
 584                         goto out;
 585
 586                 tmp = vma->vm_end;
 587                 if (tmp > end)
 588                         tmp = end;
 589                 error = mprotect_fixup(vma, &prev, nstart, tmp, newflags);
 590                 if (error)
 591                         goto out;
 592                 nstart = tmp;
 593
 594                 if (nstart < prev->vm_end)
 595                         nstart = prev->vm_end;
 596                 if (nstart >= end)
 597                         goto out;
 598
 599                 vma = prev->vm_next;
 600                 if (!vma || vma->vm_start != nstart) {
 601                         error = -ENOMEM;
 602                         goto out;
 603                 }
 604                 prot = reqprot;
 605         }
 606 out:
 607         up_write(&current->mm->mmap_sem);
 608         return error;
 609 }
 610
 611 SYSCALL_DEFINE3(mprotect, unsigned long, start, size_t, len,
 612                 unsigned long, prot)
 613 {
 614         return do_mprotect_pkey(start, len, prot, -1);
 615 }
 616
 617 #ifdef CONFIG_ARCH_HAS_PKEYS
 618
 619 SYSCALL_DEFINE4(pkey_mprotect, unsigned long, start, size_t, len,
 620                 unsigned long, prot, int, pkey)
 621 {
 622         return do_mprotect_pkey(start, len, prot, pkey);
 623 }
 624
 625 SYSCALL_DEFINE2(pkey_alloc, unsigned long, flags, unsigned long, init_val)
 626 {
 627         int pkey;
 628         int ret;
 629
 630         /* No flags supported yet. */
 631         if (flags)
 632                 return -EINVAL;
 633         /* check for unsupported init values */
 634         if (init_val & ~PKEY_ACCESS_MASK)
 635                 return -EINVAL;
 636
 637         down_write(&current->mm->mmap_sem);
 638         pkey = mm_pkey_alloc(current->mm);
 639
 640         ret = -ENOSPC;
 641         if (pkey == -1)
 642                 goto out;
 643
 644         ret = arch_set_user_pkey_access(current, pkey, init_val);
 645         if (ret) {
 646                 mm_pkey_free(current->mm, pkey);
 647                 goto out;
 648         }
 649         ret = pkey;
 650 out:
 651         up_write(&current->mm->mmap_sem);
 652         return ret;
 653 }
 654
 655 SYSCALL_DEFINE1(pkey_free, int, pkey)
 656 {
 657         int ret;
 658
 659         down_write(&current->mm->mmap_sem);
 660         ret = mm_pkey_free(current->mm, pkey);
 661         up_write(&current->mm->mmap_sem);
 662
 663         /*
 664          * We could provie warnings or errors if any VMA still
 665          * has the pkey set here.
 666          */
 667         return ret;
 668 }
 669
 670 #endif /* CONFIG_ARCH_HAS_PKEYS */