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 static inline unsigned long change_pmd_range(struct vm_area_struct *vma,
 166                 pud_t *pud, unsigned long addr, unsigned long end,
 167                 pgprot_t newprot, int dirty_accountable, int prot_numa)
 168 {
 169         pmd_t *pmd;
 170         struct mm_struct *mm = vma->vm_mm;
 171         unsigned long next;
 172         unsigned long pages = 0;
 173         unsigned long nr_huge_updates = 0;
 174         unsigned long mni_start = 0;
 175
 176         pmd = pmd_offset(pud, addr);
 177         do {
 178                 unsigned long this_pages;
 179
 180                 next = pmd_addr_end(addr, end);
 181                 if (!is_swap_pmd(*pmd) && !pmd_trans_huge(*pmd) && !pmd_devmap(*pmd)
 182                                 && pmd_none_or_clear_bad(pmd))
 183                         goto next;
 184
 185                 /* invoke the mmu notifier if the pmd is populated */
 186                 if (!mni_start) {
 187                         mni_start = addr;
 188                         mmu_notifier_invalidate_range_start(mm, mni_start, end);
 189                 }
 190
 191                 if (is_swap_pmd(*pmd) || pmd_trans_huge(*pmd) || pmd_devmap(*pmd)) {
 192                         if (next - addr != HPAGE_PMD_SIZE) {
 193                                 __split_huge_pmd(vma, pmd, addr, false, NULL);
 194                         } else {
 195                                 int nr_ptes = change_huge_pmd(vma, pmd, addr,
 196                                                 newprot, prot_numa);
 197
 198                                 if (nr_ptes) {
 199                                         if (nr_ptes == HPAGE_PMD_NR) {
 200                                                 pages += HPAGE_PMD_NR;
 201                                                 nr_huge_updates++;
 202                                         }
 203
 204                                         /* huge pmd was handled */
 205                                         goto next;
 206                                 }
 207                         }
 208                         /* fall through, the trans huge pmd just split */
 209                 }
 210                 this_pages = change_pte_range(vma, pmd, addr, next, newprot,
 211                                  dirty_accountable, prot_numa);
 212                 pages += this_pages;
 213 next:
 214                 cond_resched();
 215         } while (pmd++, addr = next, addr != end);
 216
 217         if (mni_start)
 218                 mmu_notifier_invalidate_range_end(mm, mni_start, end);
 219
 220         if (nr_huge_updates)
 221                 count_vm_numa_events(NUMA_HUGE_PTE_UPDATES, nr_huge_updates);
 222         return pages;
 223 }
 224
 225 static inline unsigned long change_pud_range(struct vm_area_struct *vma,
 226                 p4d_t *p4d, unsigned long addr, unsigned long end,
 227                 pgprot_t newprot, int dirty_accountable, int prot_numa)
 228 {
 229         pud_t *pud;
 230         unsigned long next;
 231         unsigned long pages = 0;
 232
 233         pud = pud_offset(p4d, addr);
 234         do {
 235                 next = pud_addr_end(addr, end);
 236                 if (pud_none_or_clear_bad(pud))
 237                         continue;
 238                 pages += change_pmd_range(vma, pud, addr, next, newprot,
 239                                  dirty_accountable, prot_numa);
 240         } while (pud++, addr = next, addr != end);
 241
 242         return pages;
 243 }
 244
 245 static inline unsigned long change_p4d_range(struct vm_area_struct *vma,
 246                 pgd_t *pgd, unsigned long addr, unsigned long end,
 247                 pgprot_t newprot, int dirty_accountable, int prot_numa)
 248 {
 249         p4d_t *p4d;
 250         unsigned long next;
 251         unsigned long pages = 0;
 252
 253         p4d = p4d_offset(pgd, addr);
 254         do {
 255                 next = p4d_addr_end(addr, end);
 256                 if (p4d_none_or_clear_bad(p4d))
 257                         continue;
 258                 pages += change_pud_range(vma, p4d, addr, next, newprot,
 259                                  dirty_accountable, prot_numa);
 260         } while (p4d++, addr = next, addr != end);
 261
 262         return pages;
 263 }
 264
 265 static unsigned long change_protection_range(struct vm_area_struct *vma,
 266                 unsigned long addr, unsigned long end, pgprot_t newprot,
 267                 int dirty_accountable, int prot_numa)
 268 {
 269         struct mm_struct *mm = vma->vm_mm;
 270         pgd_t *pgd;
 271         unsigned long next;
 272         unsigned long start = addr;
 273         unsigned long pages = 0;
 274
 275         BUG_ON(addr >= end);
 276         pgd = pgd_offset(mm, addr);
 277         flush_cache_range(vma, addr, end);
 278         inc_tlb_flush_pending(mm);
 279         do {
 280                 next = pgd_addr_end(addr, end);
 281                 if (pgd_none_or_clear_bad(pgd))
 282                         continue;
 283                 pages += change_p4d_range(vma, pgd, addr, next, newprot,
 284                                  dirty_accountable, prot_numa);
 285         } while (pgd++, addr = next, addr != end);
 286
 287         /* Only flush the TLB if we actually modified any entries: */
 288         if (pages)
 289                 flush_tlb_range(vma, start, end);
 290         dec_tlb_flush_pending(mm);
 291
 292         return pages;
 293 }
 294
 295 unsigned long change_protection(struct vm_area_struct *vma, unsigned long start,
 296                        unsigned long end, pgprot_t newprot,
 297                        int dirty_accountable, int prot_numa)
 298 {
 299         unsigned long pages;
 300
 301         if (is_vm_hugetlb_page(vma))
 302                 pages = hugetlb_change_protection(vma, start, end, newprot);
 303         else
 304                 pages = change_protection_range(vma, start, end, newprot, dirty_accountable, prot_numa);
 305
 306         return pages;
 307 }
 308
 309 int
 310 mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev,
 311         unsigned long start, unsigned long end, unsigned long newflags)
 312 {
 313         struct mm_struct *mm = vma->vm_mm;
 314         unsigned long oldflags = vma->vm_flags;
 315         long nrpages = (end - start) >> PAGE_SHIFT;
 316         unsigned long charged = 0;
 317         pgoff_t pgoff;
 318         int error;
 319         int dirty_accountable = 0;
 320
 321         if (newflags == oldflags) {
 322                 *pprev = vma;
 323                 return 0;
 324         }
 325
 326         /*
 327          * If we make a private mapping writable we increase our commit;
 328          * but (without finer accounting) cannot reduce our commit if we
 329          * make it unwritable again. hugetlb mapping were accounted for
 330          * even if read-only so there is no need to account for them here
 331          */
 332         if (newflags & VM_WRITE) {
 333                 /* Check space limits when area turns into data. */
 334                 if (!may_expand_vm(mm, newflags, nrpages) &&
 335                                 may_expand_vm(mm, oldflags, nrpages))
 336                         return -ENOMEM;
 337                 if (!(oldflags & (VM_ACCOUNT|VM_WRITE|VM_HUGETLB|
 338                                                 VM_SHARED|VM_NORESERVE))) {
 339                         charged = nrpages;
 340                         if (security_vm_enough_memory_mm(mm, charged))
 341                                 return -ENOMEM;
 342                         newflags |= VM_ACCOUNT;
 343                 }
 344         }
 345
 346         /*
 347          * First try to merge with previous and/or next vma.
 348          */
 349         pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
 350         *pprev = vma_merge(mm, *pprev, start, end, newflags,
 351                            vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma),
 352                            vma->vm_userfaultfd_ctx);
 353         if (*pprev) {
 354                 vma = *pprev;
 355                 VM_WARN_ON((vma->vm_flags ^ newflags) & ~VM_SOFTDIRTY);
 356                 goto success;
 357         }
 358
 359         *pprev = vma;
 360
 361         if (start != vma->vm_start) {
 362                 error = split_vma(mm, vma, start, 1);
 363                 if (error)
 364                         goto fail;
 365         }
 366
 367         if (end != vma->vm_end) {
 368                 error = split_vma(mm, vma, end, 0);
 369                 if (error)
 370                         goto fail;
 371         }
 372
 373 success:
 374         /*
 375          * vm_flags and vm_page_prot are protected by the mmap_sem
 376          * held in write mode.
 377          */
 378         vma->vm_flags = newflags;
 379         dirty_accountable = vma_wants_writenotify(vma, vma->vm_page_prot);
 380         vma_set_page_prot(vma);
 381
 382         change_protection(vma, start, end, vma->vm_page_prot,
 383                           dirty_accountable, 0);
 384
 385         /*
 386          * Private VM_LOCKED VMA becoming writable: trigger COW to avoid major
 387          * fault on access.
 388          */
 389         if ((oldflags & (VM_WRITE | VM_SHARED | VM_LOCKED)) == VM_LOCKED &&
 390                         (newflags & VM_WRITE)) {
 391                 populate_vma_page_range(vma, start, end, NULL);
 392         }
 393
 394         vm_stat_account(mm, oldflags, -nrpages);
 395         vm_stat_account(mm, newflags, nrpages);
 396         perf_event_mmap(vma);
 397         return 0;
 398
 399 fail:
 400         vm_unacct_memory(charged);
 401         return error;
 402 }
 403
 404 /*
 405  * pkey==-1 when doing a legacy mprotect()
 406  */
 407 static int do_mprotect_pkey(unsigned long start, size_t len,
 408                 unsigned long prot, int pkey)
 409 {
 410         unsigned long nstart, end, tmp, reqprot;
 411         struct vm_area_struct *vma, *prev;
 412         int error = -EINVAL;
 413         const int grows = prot & (PROT_GROWSDOWN|PROT_GROWSUP);
 414         const bool rier = (current->personality & READ_IMPLIES_EXEC) &&
 415                                 (prot & PROT_READ);
 416
 417         prot &= ~(PROT_GROWSDOWN|PROT_GROWSUP);
 418         if (grows == (PROT_GROWSDOWN|PROT_GROWSUP)) /* can't be both */
 419                 return -EINVAL;
 420
 421         if (start & ~PAGE_MASK)
 422                 return -EINVAL;
 423         if (!len)
 424                 return 0;
 425         len = PAGE_ALIGN(len);
 426         end = start + len;
 427         if (end <= start)
 428                 return -ENOMEM;
 429         if (!arch_validate_prot(prot, start))
 430                 return -EINVAL;
 431
 432         reqprot = prot;
 433
 434         if (down_write_killable(&current->mm->mmap_sem))
 435                 return -EINTR;
 436
 437         /*
 438          * If userspace did not allocate the pkey, do not let
 439          * them use it here.
 440          */
 441         error = -EINVAL;
 442         if ((pkey != -1) && !mm_pkey_is_allocated(current->mm, pkey))
 443                 goto out;
 444
 445         vma = find_vma(current->mm, start);
 446         error = -ENOMEM;
 447         if (!vma)
 448                 goto out;
 449         prev = vma->vm_prev;
 450         if (unlikely(grows & PROT_GROWSDOWN)) {
 451                 if (vma->vm_start >= end)
 452                         goto out;
 453                 start = vma->vm_start;
 454                 error = -EINVAL;
 455                 if (!(vma->vm_flags & VM_GROWSDOWN))
 456                         goto out;
 457         } else {
 458                 if (vma->vm_start > start)
 459                         goto out;
 460                 if (unlikely(grows & PROT_GROWSUP)) {
 461                         end = vma->vm_end;
 462                         error = -EINVAL;
 463                         if (!(vma->vm_flags & VM_GROWSUP))
 464                                 goto out;
 465                 }
 466         }
 467         if (start > vma->vm_start)
 468                 prev = vma;
 469
 470         for (nstart = start ; ; ) {
 471                 unsigned long mask_off_old_flags;
 472                 unsigned long newflags;
 473                 int new_vma_pkey;
 474
 475                 /* Here we know that vma->vm_start <= nstart < vma->vm_end. */
 476
 477                 /* Does the application expect PROT_READ to imply PROT_EXEC */
 478                 if (rier && (vma->vm_flags & VM_MAYEXEC))
 479                         prot |= PROT_EXEC;
 480
 481                 /*
 482                  * Each mprotect() call explicitly passes r/w/x permissions.
 483                  * If a permission is not passed to mprotect(), it must be
 484                  * cleared from the VMA.
 485                  */
 486                 mask_off_old_flags = VM_READ | VM_WRITE | VM_EXEC |
 487                                         VM_FLAGS_CLEAR;
 488
 489                 new_vma_pkey = arch_override_mprotect_pkey(vma, prot, pkey);
 490                 newflags = calc_vm_prot_bits(prot, new_vma_pkey);
 491                 newflags |= (vma->vm_flags & ~mask_off_old_flags);
 492
 493                 /* newflags >> 4 shift VM_MAY% in place of VM_% */
 494                 if ((newflags & ~(newflags >> 4)) & (VM_READ | VM_WRITE | VM_EXEC)) {
 495                         error = -EACCES;
 496                         goto out;
 497                 }
 498
 499                 error = security_file_mprotect(vma, reqprot, prot);
 500                 if (error)
 501                         goto out;
 502
 503                 tmp = vma->vm_end;
 504                 if (tmp > end)
 505                         tmp = end;
 506                 error = mprotect_fixup(vma, &prev, nstart, tmp, newflags);
 507                 if (error)
 508                         goto out;
 509                 nstart = tmp;
 510
 511                 if (nstart < prev->vm_end)
 512                         nstart = prev->vm_end;
 513                 if (nstart >= end)
 514                         goto out;
 515
 516                 vma = prev->vm_next;
 517                 if (!vma || vma->vm_start != nstart) {
 518                         error = -ENOMEM;
 519                         goto out;
 520                 }
 521                 prot = reqprot;
 522         }
 523 out:
 524         up_write(&current->mm->mmap_sem);
 525         return error;
 526 }
 527
 528 SYSCALL_DEFINE3(mprotect, unsigned long, start, size_t, len,
 529                 unsigned long, prot)
 530 {
 531         return do_mprotect_pkey(start, len, prot, -1);
 532 }
 533
 534 #ifdef CONFIG_ARCH_HAS_PKEYS
 535
 536 SYSCALL_DEFINE4(pkey_mprotect, unsigned long, start, size_t, len,
 537                 unsigned long, prot, int, pkey)
 538 {
 539         return do_mprotect_pkey(start, len, prot, pkey);
 540 }
 541
 542 SYSCALL_DEFINE2(pkey_alloc, unsigned long, flags, unsigned long, init_val)
 543 {
 544         int pkey;
 545         int ret;
 546
 547         /* No flags supported yet. */
 548         if (flags)
 549                 return -EINVAL;
 550         /* check for unsupported init values */
 551         if (init_val & ~PKEY_ACCESS_MASK)
 552                 return -EINVAL;
 553
 554         down_write(&current->mm->mmap_sem);
 555         pkey = mm_pkey_alloc(current->mm);
 556
 557         ret = -ENOSPC;
 558         if (pkey == -1)
 559                 goto out;
 560
 561         ret = arch_set_user_pkey_access(current, pkey, init_val);
 562         if (ret) {
 563                 mm_pkey_free(current->mm, pkey);
 564                 goto out;
 565         }
 566         ret = pkey;
 567 out:
 568         up_write(&current->mm->mmap_sem);
 569         return ret;
 570 }
 571
 572 SYSCALL_DEFINE1(pkey_free, int, pkey)
 573 {
 574         int ret;
 575
 576         down_write(&current->mm->mmap_sem);
 577         ret = mm_pkey_free(current->mm, pkey);
 578         up_write(&current->mm->mmap_sem);
 579
 580         /*
 581          * We could provie warnings or errors if any VMA still
 582          * has the pkey set here.
 583          */
 584         return ret;
 585 }
 586
 587 #endif /* CONFIG_ARCH_HAS_PKEYS */