1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * mm/mprotect.c 4 * 5 * (C) Copyright 1994 Linus Torvalds 6 * (C) Copyright 2002 Christoph Hellwig 7 * 8 * Address space accounting code <alan@lxorguk.ukuu.org.uk> 9 * (C) Copyright 2002 Red Hat Inc, All Rights Reserved 10 */ 11 12 #include <linux/pagewalk.h> 13 #include <linux/hugetlb.h> 14 #include <linux/shm.h> 15 #include <linux/mman.h> 16 #include <linux/fs.h> 17 #include <linux/highmem.h> 18 #include <linux/security.h> 19 #include <linux/mempolicy.h> 20 #include <linux/personality.h> 21 #include <linux/syscalls.h> 22 #include <linux/swap.h> 23 #include <linux/swapops.h> 24 #include <linux/mmu_notifier.h> 25 #include <linux/migrate.h> 26 #include <linux/perf_event.h> 27 #include <linux/pkeys.h> 28 #include <linux/ksm.h> 29 #include <linux/uaccess.h> 30 #include <linux/mm_inline.h> 31 #include <linux/pgtable.h> 32 #include <linux/sched/sysctl.h> 33 #include <linux/userfaultfd_k.h> 34 #include <linux/memory-tiers.h> 35 #include <asm/cacheflush.h> 36 #include <asm/mmu_context.h> 37 #include <asm/tlbflush.h> 38 #include <asm/tlb.h> 39 40 #include "internal.h" 41 42 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 */ 940