1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * mm/mprotect.c 4 * 5 * (C) Copyright 1994 Linus Torvalds 6 * (C) Copyright 2002 Christoph Hellwig 7 * 8 * Address space accounting code <alan@lxorguk.ukuu.org.uk> 9 * (C) Copyright 2002 Red Hat Inc, All Rights Reserved 10 */ 11 12 #include <linux/pagewalk.h> 13 #include <linux/hugetlb.h> 14 #include <linux/shm.h> 15 #include <linux/mman.h> 16 #include <linux/fs.h> 17 #include <linux/highmem.h> 18 #include <linux/security.h> 19 #include <linux/mempolicy.h> 20 #include <linux/personality.h> 21 #include <linux/syscalls.h> 22 #include <linux/swap.h> 23 #include <linux/swapops.h> 24 #include <linux/mmu_notifier.h> 25 #include <linux/migrate.h> 26 #include <linux/perf_event.h> 27 #include <linux/pkeys.h> 28 #include <linux/ksm.h> 29 #include <linux/uaccess.h> 30 #include <linux/mm_inline.h> 31 #include <linux/pgtable.h> 32 #include <linux/sched/sysctl.h> 33 #include <linux/userfaultfd_k.h> 34 #include <linux/memory-tiers.h> 35 #include <uapi/linux/mman.h> 36 #include <asm/cacheflush.h> 37 #include <asm/mmu_context.h> 38 #include <asm/tlbflush.h> 39 #include <asm/tlb.h> 40 41 #include "internal.h" 42 43 static bool maybe_change_pte_writable(struct vm_area_struct *vma, pte_t pte) 44 { 45 if (WARN_ON_ONCE(!(vma->vm_flags & VM_WRITE))) 46 return false; 47 48 /* Don't touch entries that are not even readable. */ 49 if (pte_protnone(pte)) 50 return false; 51 52 /* Do we need write faults for softdirty tracking? */ 53 if (pte_needs_soft_dirty_wp(vma, pte)) 54 return false; 55 56 /* Do we need write faults for uffd-wp tracking? */ 57 if (userfaultfd_pte_wp(vma, pte)) 58 return false; 59 60 return true; 61 } 62 63 static bool can_change_private_pte_writable(struct vm_area_struct *vma, 64 unsigned long addr, pte_t pte) 65 { 66 struct page *page; 67 68 if (!maybe_change_pte_writable(vma, pte)) 69 return false; 70 71 /* 72 * Writable MAP_PRIVATE mapping: We can only special-case on 73 * exclusive anonymous pages, because we know that our 74 * write-fault handler similarly would map them writable without 75 * any additional checks while holding the PT lock. 76 */ 77 page = vm_normal_page(vma, addr, pte); 78 return page && PageAnon(page) && PageAnonExclusive(page); 79 } 80 81 static bool can_change_shared_pte_writable(struct vm_area_struct *vma, 82 pte_t pte) 83 { 84 if (!maybe_change_pte_writable(vma, pte)) 85 return false; 86 87 VM_WARN_ON_ONCE(is_zero_pfn(pte_pfn(pte)) && pte_dirty(pte)); 88 89 /* 90 * Writable MAP_SHARED mapping: "clean" might indicate that the FS still 91 * needs a real write-fault for writenotify 92 * (see vma_wants_writenotify()). If "dirty", the assumption is that the 93 * FS was already notified and we can simply mark the PTE writable 94 * just like the write-fault handler would do. 95 */ 96 return pte_dirty(pte); 97 } 98 99 bool can_change_pte_writable(struct vm_area_struct *vma, unsigned long addr, 100 pte_t pte) 101 { 102 if (!(vma->vm_flags & VM_SHARED)) 103 return can_change_private_pte_writable(vma, addr, pte); 104 105 return can_change_shared_pte_writable(vma, pte); 106 } 107 108 static int mprotect_folio_pte_batch(struct folio *folio, pte_t *ptep, 109 pte_t pte, int max_nr_ptes, fpb_t flags) 110 { 111 /* No underlying folio, so cannot batch */ 112 if (!folio) 113 return 1; 114 115 if (!folio_test_large(folio)) 116 return 1; 117 118 return folio_pte_batch_flags(folio, NULL, ptep, &pte, max_nr_ptes, flags); 119 } 120 121 static bool prot_numa_skip(struct vm_area_struct *vma, unsigned long addr, 122 pte_t oldpte, pte_t *pte, int target_node, 123 struct folio *folio) 124 { 125 bool ret = true; 126 bool toptier; 127 int nid; 128 129 /* Avoid TLB flush if possible */ 130 if (pte_protnone(oldpte)) 131 goto skip; 132 133 if (!folio) 134 goto skip; 135 136 if (folio_is_zone_device(folio) || folio_test_ksm(folio)) 137 goto skip; 138 139 /* Also skip shared copy-on-write pages */ 140 if (is_cow_mapping(vma->vm_flags) && 141 (folio_maybe_dma_pinned(folio) || folio_maybe_mapped_shared(folio))) 142 goto skip; 143 144 /* 145 * While migration can move some dirty pages, 146 * it cannot move them all from MIGRATE_ASYNC 147 * context. 148 */ 149 if (folio_is_file_lru(folio) && folio_test_dirty(folio)) 150 goto skip; 151 152 /* 153 * Don't mess with PTEs if page is already on the node 154 * a single-threaded process is running on. 155 */ 156 nid = folio_nid(folio); 157 if (target_node == nid) 158 goto skip; 159 160 toptier = node_is_toptier(nid); 161 162 /* 163 * Skip scanning top tier node if normal numa 164 * balancing is disabled 165 */ 166 if (!(sysctl_numa_balancing_mode & NUMA_BALANCING_NORMAL) && toptier) 167 goto skip; 168 169 ret = false; 170 if (folio_use_access_time(folio)) 171 folio_xchg_access_time(folio, jiffies_to_msecs(jiffies)); 172 173 skip: 174 return ret; 175 } 176 177 /* Set nr_ptes number of ptes, starting from idx */ 178 static void prot_commit_flush_ptes(struct vm_area_struct *vma, unsigned long addr, 179 pte_t *ptep, pte_t oldpte, pte_t ptent, int nr_ptes, 180 int idx, bool set_write, struct mmu_gather *tlb) 181 { 182 /* 183 * Advance the position in the batch by idx; note that if idx > 0, 184 * then the nr_ptes passed here is <= batch size - idx. 185 */ 186 addr += idx * PAGE_SIZE; 187 ptep += idx; 188 oldpte = pte_advance_pfn(oldpte, idx); 189 ptent = pte_advance_pfn(ptent, idx); 190 191 if (set_write) 192 ptent = pte_mkwrite(ptent, vma); 193 194 modify_prot_commit_ptes(vma, addr, ptep, oldpte, ptent, nr_ptes); 195 if (pte_needs_flush(oldpte, ptent)) 196 tlb_flush_pte_range(tlb, addr, nr_ptes * PAGE_SIZE); 197 } 198 199 /* 200 * Get max length of consecutive ptes pointing to PageAnonExclusive() pages or 201 * !PageAnonExclusive() pages, starting from start_idx. Caller must enforce 202 * that the ptes point to consecutive pages of the same anon large folio. 203 */ 204 static int page_anon_exclusive_sub_batch(int start_idx, int max_len, 205 struct page *first_page, bool expected_anon_exclusive) 206 { 207 int idx; 208 209 for (idx = start_idx + 1; idx < start_idx + max_len; ++idx) { 210 if (expected_anon_exclusive != PageAnonExclusive(first_page + idx)) 211 break; 212 } 213 return idx - start_idx; 214 } 215 216 /* 217 * This function is a result of trying our very best to retain the 218 * "avoid the write-fault handler" optimization. In can_change_pte_writable(), 219 * if the vma is a private vma, and we cannot determine whether to change 220 * the pte to writable just from the vma and the pte, we then need to look 221 * at the actual page pointed to by the pte. Unfortunately, if we have a 222 * batch of ptes pointing to consecutive pages of the same anon large folio, 223 * the anon-exclusivity (or the negation) of the first page does not guarantee 224 * the anon-exclusivity (or the negation) of the other pages corresponding to 225 * the pte batch; hence in this case it is incorrect to decide to change or 226 * not change the ptes to writable just by using information from the first 227 * pte of the batch. Therefore, we must individually check all pages and 228 * retrieve sub-batches. 229 */ 230 static void commit_anon_folio_batch(struct vm_area_struct *vma, 231 struct folio *folio, struct page *first_page, unsigned long addr, pte_t *ptep, 232 pte_t oldpte, pte_t ptent, int nr_ptes, struct mmu_gather *tlb) 233 { 234 bool expected_anon_exclusive; 235 int sub_batch_idx = 0; 236 int len; 237 238 while (nr_ptes) { 239 expected_anon_exclusive = PageAnonExclusive(first_page + sub_batch_idx); 240 len = page_anon_exclusive_sub_batch(sub_batch_idx, nr_ptes, 241 first_page, expected_anon_exclusive); 242 prot_commit_flush_ptes(vma, addr, ptep, oldpte, ptent, len, 243 sub_batch_idx, expected_anon_exclusive, tlb); 244 sub_batch_idx += len; 245 nr_ptes -= len; 246 } 247 } 248 249 static void set_write_prot_commit_flush_ptes(struct vm_area_struct *vma, 250 struct folio *folio, struct page *page, unsigned long addr, pte_t *ptep, 251 pte_t oldpte, pte_t ptent, int nr_ptes, struct mmu_gather *tlb) 252 { 253 bool set_write; 254 255 if (vma->vm_flags & VM_SHARED) { 256 set_write = can_change_shared_pte_writable(vma, ptent); 257 prot_commit_flush_ptes(vma, addr, ptep, oldpte, ptent, nr_ptes, 258 /* idx = */ 0, set_write, tlb); 259 return; 260 } 261 262 set_write = maybe_change_pte_writable(vma, ptent) && 263 (folio && folio_test_anon(folio)); 264 if (!set_write) { 265 prot_commit_flush_ptes(vma, addr, ptep, oldpte, ptent, nr_ptes, 266 /* idx = */ 0, set_write, tlb); 267 return; 268 } 269 commit_anon_folio_batch(vma, folio, page, addr, ptep, oldpte, ptent, nr_ptes, tlb); 270 } 271 272 static long change_pte_range(struct mmu_gather *tlb, 273 struct vm_area_struct *vma, pmd_t *pmd, unsigned long addr, 274 unsigned long end, pgprot_t newprot, unsigned long cp_flags) 275 { 276 pte_t *pte, oldpte; 277 spinlock_t *ptl; 278 long pages = 0; 279 int target_node = NUMA_NO_NODE; 280 bool prot_numa = cp_flags & MM_CP_PROT_NUMA; 281 bool uffd_wp = cp_flags & MM_CP_UFFD_WP; 282 bool uffd_wp_resolve = cp_flags & MM_CP_UFFD_WP_RESOLVE; 283 int nr_ptes; 284 285 tlb_change_page_size(tlb, PAGE_SIZE); 286 pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); 287 if (!pte) 288 return -EAGAIN; 289 290 /* Get target node for single threaded private VMAs */ 291 if (prot_numa && !(vma->vm_flags & VM_SHARED) && 292 atomic_read(&vma->vm_mm->mm_users) == 1) 293 target_node = numa_node_id(); 294 295 flush_tlb_batched_pending(vma->vm_mm); 296 arch_enter_lazy_mmu_mode(); 297 do { 298 nr_ptes = 1; 299 oldpte = ptep_get(pte); 300 if (pte_present(oldpte)) { 301 const fpb_t flags = FPB_RESPECT_SOFT_DIRTY | FPB_RESPECT_WRITE; 302 int max_nr_ptes = (end - addr) >> PAGE_SHIFT; 303 struct folio *folio = NULL; 304 struct page *page; 305 pte_t ptent; 306 307 page = vm_normal_page(vma, addr, oldpte); 308 if (page) 309 folio = page_folio(page); 310 /* 311 * Avoid trapping faults against the zero or KSM 312 * pages. See similar comment in change_huge_pmd. 313 */ 314 if (prot_numa) { 315 int ret = prot_numa_skip(vma, addr, oldpte, pte, 316 target_node, folio); 317 if (ret) { 318 319 /* determine batch to skip */ 320 nr_ptes = mprotect_folio_pte_batch(folio, 321 pte, oldpte, max_nr_ptes, /* flags = */ 0); 322 continue; 323 } 324 } 325 326 nr_ptes = mprotect_folio_pte_batch(folio, pte, oldpte, max_nr_ptes, flags); 327 328 oldpte = modify_prot_start_ptes(vma, addr, pte, nr_ptes); 329 ptent = pte_modify(oldpte, newprot); 330 331 if (uffd_wp) 332 ptent = pte_mkuffd_wp(ptent); 333 else if (uffd_wp_resolve) 334 ptent = pte_clear_uffd_wp(ptent); 335 336 /* 337 * In some writable, shared mappings, we might want 338 * to catch actual write access -- see 339 * vma_wants_writenotify(). 340 * 341 * In all writable, private mappings, we have to 342 * properly handle COW. 343 * 344 * In both cases, we can sometimes still change PTEs 345 * writable and avoid the write-fault handler, for 346 * example, if a PTE is already dirty and no other 347 * COW or special handling is required. 348 */ 349 if ((cp_flags & MM_CP_TRY_CHANGE_WRITABLE) && 350 !pte_write(ptent)) 351 set_write_prot_commit_flush_ptes(vma, folio, page, 352 addr, pte, oldpte, ptent, nr_ptes, tlb); 353 else 354 prot_commit_flush_ptes(vma, addr, pte, oldpte, ptent, 355 nr_ptes, /* idx = */ 0, /* set_write = */ false, tlb); 356 pages += nr_ptes; 357 } else if (is_swap_pte(oldpte)) { 358 swp_entry_t entry = pte_to_swp_entry(oldpte); 359 pte_t newpte; 360 361 if (is_writable_migration_entry(entry)) { 362 struct folio *folio = pfn_swap_entry_folio(entry); 363 364 /* 365 * A protection check is difficult so 366 * just be safe and disable write 367 */ 368 if (folio_test_anon(folio)) 369 entry = make_readable_exclusive_migration_entry( 370 swp_offset(entry)); 371 else 372 entry = make_readable_migration_entry(swp_offset(entry)); 373 newpte = swp_entry_to_pte(entry); 374 if (pte_swp_soft_dirty(oldpte)) 375 newpte = pte_swp_mksoft_dirty(newpte); 376 } else if (is_writable_device_private_entry(entry)) { 377 /* 378 * We do not preserve soft-dirtiness. See 379 * copy_nonpresent_pte() for explanation. 380 */ 381 entry = make_readable_device_private_entry( 382 swp_offset(entry)); 383 newpte = swp_entry_to_pte(entry); 384 if (pte_swp_uffd_wp(oldpte)) 385 newpte = pte_swp_mkuffd_wp(newpte); 386 } else if (is_pte_marker_entry(entry)) { 387 /* 388 * Ignore error swap entries unconditionally, 389 * because any access should sigbus/sigsegv 390 * anyway. 391 */ 392 if (is_poisoned_swp_entry(entry) || 393 is_guard_swp_entry(entry)) 394 continue; 395 /* 396 * If this is uffd-wp pte marker and we'd like 397 * to unprotect it, drop it; the next page 398 * fault will trigger without uffd trapping. 399 */ 400 if (uffd_wp_resolve) { 401 pte_clear(vma->vm_mm, addr, pte); 402 pages++; 403 } 404 continue; 405 } else { 406 newpte = oldpte; 407 } 408 409 if (uffd_wp) 410 newpte = pte_swp_mkuffd_wp(newpte); 411 else if (uffd_wp_resolve) 412 newpte = pte_swp_clear_uffd_wp(newpte); 413 414 if (!pte_same(oldpte, newpte)) { 415 set_pte_at(vma->vm_mm, addr, pte, newpte); 416 pages++; 417 } 418 } else { 419 /* It must be an none page, or what else?.. */ 420 WARN_ON_ONCE(!pte_none(oldpte)); 421 422 /* 423 * Nobody plays with any none ptes besides 424 * userfaultfd when applying the protections. 425 */ 426 if (likely(!uffd_wp)) 427 continue; 428 429 if (userfaultfd_wp_use_markers(vma)) { 430 /* 431 * For file-backed mem, we need to be able to 432 * wr-protect a none pte, because even if the 433 * pte is none, the page/swap cache could 434 * exist. Doing that by install a marker. 435 */ 436 set_pte_at(vma->vm_mm, addr, pte, 437 make_pte_marker(PTE_MARKER_UFFD_WP)); 438 pages++; 439 } 440 } 441 } while (pte += nr_ptes, addr += nr_ptes * PAGE_SIZE, addr != end); 442 arch_leave_lazy_mmu_mode(); 443 pte_unmap_unlock(pte - 1, ptl); 444 445 return pages; 446 } 447 448 /* 449 * Return true if we want to split THPs into PTE mappings in change 450 * protection procedure, false otherwise. 451 */ 452 static inline bool 453 pgtable_split_needed(struct vm_area_struct *vma, unsigned long cp_flags) 454 { 455 /* 456 * pte markers only resides in pte level, if we need pte markers, 457 * we need to split. For example, we cannot wr-protect a file thp 458 * (e.g. 2M shmem) because file thp is handled differently when 459 * split by erasing the pmd so far. 460 */ 461 return (cp_flags & MM_CP_UFFD_WP) && !vma_is_anonymous(vma); 462 } 463 464 /* 465 * Return true if we want to populate pgtables in change protection 466 * procedure, false otherwise 467 */ 468 static inline bool 469 pgtable_populate_needed(struct vm_area_struct *vma, unsigned long cp_flags) 470 { 471 /* If not within ioctl(UFFDIO_WRITEPROTECT), then don't bother */ 472 if (!(cp_flags & MM_CP_UFFD_WP)) 473 return false; 474 475 /* Populate if the userfaultfd mode requires pte markers */ 476 return userfaultfd_wp_use_markers(vma); 477 } 478 479 /* 480 * Populate the pgtable underneath for whatever reason if requested. 481 * When {pte|pmd|...}_alloc() failed we treat it the same way as pgtable 482 * allocation failures during page faults by kicking OOM and returning 483 * error. 484 */ 485 #define change_pmd_prepare(vma, pmd, cp_flags) \ 486 ({ \ 487 long err = 0; \ 488 if (unlikely(pgtable_populate_needed(vma, cp_flags))) { \ 489 if (pte_alloc(vma->vm_mm, pmd)) \ 490 err = -ENOMEM; \ 491 } \ 492 err; \ 493 }) 494 495 /* 496 * This is the general pud/p4d/pgd version of change_pmd_prepare(). We need to 497 * have separate change_pmd_prepare() because pte_alloc() returns 0 on success, 498 * while {pmd|pud|p4d}_alloc() returns the valid pointer on success. 499 */ 500 #define change_prepare(vma, high, low, addr, cp_flags) \ 501 ({ \ 502 long err = 0; \ 503 if (unlikely(pgtable_populate_needed(vma, cp_flags))) { \ 504 low##_t *p = low##_alloc(vma->vm_mm, high, addr); \ 505 if (p == NULL) \ 506 err = -ENOMEM; \ 507 } \ 508 err; \ 509 }) 510 511 static inline long change_pmd_range(struct mmu_gather *tlb, 512 struct vm_area_struct *vma, pud_t *pud, unsigned long addr, 513 unsigned long end, pgprot_t newprot, unsigned long cp_flags) 514 { 515 pmd_t *pmd; 516 unsigned long next; 517 long pages = 0; 518 unsigned long nr_huge_updates = 0; 519 520 pmd = pmd_offset(pud, addr); 521 do { 522 long ret; 523 pmd_t _pmd; 524 again: 525 next = pmd_addr_end(addr, end); 526 527 ret = change_pmd_prepare(vma, pmd, cp_flags); 528 if (ret) { 529 pages = ret; 530 break; 531 } 532 533 if (pmd_none(*pmd)) 534 goto next; 535 536 _pmd = pmdp_get_lockless(pmd); 537 if (is_swap_pmd(_pmd) || pmd_trans_huge(_pmd)) { 538 if ((next - addr != HPAGE_PMD_SIZE) || 539 pgtable_split_needed(vma, cp_flags)) { 540 __split_huge_pmd(vma, pmd, addr, false); 541 /* 542 * For file-backed, the pmd could have been 543 * cleared; make sure pmd populated if 544 * necessary, then fall-through to pte level. 545 */ 546 ret = change_pmd_prepare(vma, pmd, cp_flags); 547 if (ret) { 548 pages = ret; 549 break; 550 } 551 } else { 552 ret = change_huge_pmd(tlb, vma, pmd, 553 addr, newprot, cp_flags); 554 if (ret) { 555 if (ret == HPAGE_PMD_NR) { 556 pages += HPAGE_PMD_NR; 557 nr_huge_updates++; 558 } 559 560 /* huge pmd was handled */ 561 goto next; 562 } 563 } 564 /* fall through, the trans huge pmd just split */ 565 } 566 567 ret = change_pte_range(tlb, vma, pmd, addr, next, newprot, 568 cp_flags); 569 if (ret < 0) 570 goto again; 571 pages += ret; 572 next: 573 cond_resched(); 574 } while (pmd++, addr = next, addr != end); 575 576 if (nr_huge_updates) 577 count_vm_numa_events(NUMA_HUGE_PTE_UPDATES, nr_huge_updates); 578 return pages; 579 } 580 581 static inline long change_pud_range(struct mmu_gather *tlb, 582 struct vm_area_struct *vma, p4d_t *p4d, unsigned long addr, 583 unsigned long end, pgprot_t newprot, unsigned long cp_flags) 584 { 585 struct mmu_notifier_range range; 586 pud_t *pudp, pud; 587 unsigned long next; 588 long pages = 0, ret; 589 590 range.start = 0; 591 592 pudp = pud_offset(p4d, addr); 593 do { 594 again: 595 next = pud_addr_end(addr, end); 596 ret = change_prepare(vma, pudp, pmd, addr, cp_flags); 597 if (ret) { 598 pages = ret; 599 break; 600 } 601 602 pud = READ_ONCE(*pudp); 603 if (pud_none(pud)) 604 continue; 605 606 if (!range.start) { 607 mmu_notifier_range_init(&range, 608 MMU_NOTIFY_PROTECTION_VMA, 0, 609 vma->vm_mm, addr, end); 610 mmu_notifier_invalidate_range_start(&range); 611 } 612 613 if (pud_leaf(pud)) { 614 if ((next - addr != PUD_SIZE) || 615 pgtable_split_needed(vma, cp_flags)) { 616 __split_huge_pud(vma, pudp, addr); 617 goto again; 618 } else { 619 ret = change_huge_pud(tlb, vma, pudp, 620 addr, newprot, cp_flags); 621 if (ret == 0) 622 goto again; 623 /* huge pud was handled */ 624 if (ret == HPAGE_PUD_NR) 625 pages += HPAGE_PUD_NR; 626 continue; 627 } 628 } 629 630 pages += change_pmd_range(tlb, vma, pudp, addr, next, newprot, 631 cp_flags); 632 } while (pudp++, addr = next, addr != end); 633 634 if (range.start) 635 mmu_notifier_invalidate_range_end(&range); 636 637 return pages; 638 } 639 640 static inline long change_p4d_range(struct mmu_gather *tlb, 641 struct vm_area_struct *vma, pgd_t *pgd, unsigned long addr, 642 unsigned long end, pgprot_t newprot, unsigned long cp_flags) 643 { 644 p4d_t *p4d; 645 unsigned long next; 646 long pages = 0, ret; 647 648 p4d = p4d_offset(pgd, addr); 649 do { 650 next = p4d_addr_end(addr, end); 651 ret = change_prepare(vma, p4d, pud, addr, cp_flags); 652 if (ret) 653 return ret; 654 if (p4d_none_or_clear_bad(p4d)) 655 continue; 656 pages += change_pud_range(tlb, vma, p4d, addr, next, newprot, 657 cp_flags); 658 } while (p4d++, addr = next, addr != end); 659 660 return pages; 661 } 662 663 static long change_protection_range(struct mmu_gather *tlb, 664 struct vm_area_struct *vma, unsigned long addr, 665 unsigned long end, pgprot_t newprot, unsigned long cp_flags) 666 { 667 struct mm_struct *mm = vma->vm_mm; 668 pgd_t *pgd; 669 unsigned long next; 670 long pages = 0, ret; 671 672 BUG_ON(addr >= end); 673 pgd = pgd_offset(mm, addr); 674 tlb_start_vma(tlb, vma); 675 do { 676 next = pgd_addr_end(addr, end); 677 ret = change_prepare(vma, pgd, p4d, addr, cp_flags); 678 if (ret) { 679 pages = ret; 680 break; 681 } 682 if (pgd_none_or_clear_bad(pgd)) 683 continue; 684 pages += change_p4d_range(tlb, vma, pgd, addr, next, newprot, 685 cp_flags); 686 } while (pgd++, addr = next, addr != end); 687 688 tlb_end_vma(tlb, vma); 689 690 return pages; 691 } 692 693 long change_protection(struct mmu_gather *tlb, 694 struct vm_area_struct *vma, unsigned long start, 695 unsigned long end, unsigned long cp_flags) 696 { 697 pgprot_t newprot = vma->vm_page_prot; 698 long pages; 699 700 BUG_ON((cp_flags & MM_CP_UFFD_WP_ALL) == MM_CP_UFFD_WP_ALL); 701 702 #ifdef CONFIG_NUMA_BALANCING 703 /* 704 * Ordinary protection updates (mprotect, uffd-wp, softdirty tracking) 705 * are expected to reflect their requirements via VMA flags such that 706 * vma_set_page_prot() will adjust vma->vm_page_prot accordingly. 707 */ 708 if (cp_flags & MM_CP_PROT_NUMA) 709 newprot = PAGE_NONE; 710 #else 711 WARN_ON_ONCE(cp_flags & MM_CP_PROT_NUMA); 712 #endif 713 714 if (is_vm_hugetlb_page(vma)) 715 pages = hugetlb_change_protection(vma, start, end, newprot, 716 cp_flags); 717 else 718 pages = change_protection_range(tlb, vma, start, end, newprot, 719 cp_flags); 720 721 return pages; 722 } 723 724 static int prot_none_pte_entry(pte_t *pte, unsigned long addr, 725 unsigned long next, struct mm_walk *walk) 726 { 727 return pfn_modify_allowed(pte_pfn(ptep_get(pte)), 728 *(pgprot_t *)(walk->private)) ? 729 0 : -EACCES; 730 } 731 732 static int prot_none_hugetlb_entry(pte_t *pte, unsigned long hmask, 733 unsigned long addr, unsigned long next, 734 struct mm_walk *walk) 735 { 736 return pfn_modify_allowed(pte_pfn(ptep_get(pte)), 737 *(pgprot_t *)(walk->private)) ? 738 0 : -EACCES; 739 } 740 741 static int prot_none_test(unsigned long addr, unsigned long next, 742 struct mm_walk *walk) 743 { 744 return 0; 745 } 746 747 static const struct mm_walk_ops prot_none_walk_ops = { 748 .pte_entry = prot_none_pte_entry, 749 .hugetlb_entry = prot_none_hugetlb_entry, 750 .test_walk = prot_none_test, 751 .walk_lock = PGWALK_WRLOCK, 752 }; 753 754 int 755 mprotect_fixup(struct vma_iterator *vmi, struct mmu_gather *tlb, 756 struct vm_area_struct *vma, struct vm_area_struct **pprev, 757 unsigned long start, unsigned long end, vm_flags_t newflags) 758 { 759 struct mm_struct *mm = vma->vm_mm; 760 vm_flags_t oldflags = READ_ONCE(vma->vm_flags); 761 long nrpages = (end - start) >> PAGE_SHIFT; 762 unsigned int mm_cp_flags = 0; 763 unsigned long charged = 0; 764 int error; 765 766 if (vma_is_sealed(vma)) 767 return -EPERM; 768 769 if (newflags == oldflags) { 770 *pprev = vma; 771 return 0; 772 } 773 774 /* 775 * Do PROT_NONE PFN permission checks here when we can still 776 * bail out without undoing a lot of state. This is a rather 777 * uncommon case, so doesn't need to be very optimized. 778 */ 779 if (arch_has_pfn_modify_check() && 780 (oldflags & (VM_PFNMAP|VM_MIXEDMAP)) && 781 (newflags & VM_ACCESS_FLAGS) == 0) { 782 pgprot_t new_pgprot = vm_get_page_prot(newflags); 783 784 error = walk_page_range(current->mm, start, end, 785 &prot_none_walk_ops, &new_pgprot); 786 if (error) 787 return error; 788 } 789 790 /* 791 * If we make a private mapping writable we increase our commit; 792 * but (without finer accounting) cannot reduce our commit if we 793 * make it unwritable again except in the anonymous case where no 794 * anon_vma has yet to be assigned. 795 * 796 * hugetlb mapping were accounted for even if read-only so there is 797 * no need to account for them here. 798 */ 799 if (newflags & VM_WRITE) { 800 /* Check space limits when area turns into data. */ 801 if (!may_expand_vm(mm, newflags, nrpages) && 802 may_expand_vm(mm, oldflags, nrpages)) 803 return -ENOMEM; 804 if (!(oldflags & (VM_ACCOUNT|VM_WRITE|VM_HUGETLB| 805 VM_SHARED|VM_NORESERVE))) { 806 charged = nrpages; 807 if (security_vm_enough_memory_mm(mm, charged)) 808 return -ENOMEM; 809 newflags |= VM_ACCOUNT; 810 } 811 } else if ((oldflags & VM_ACCOUNT) && vma_is_anonymous(vma) && 812 !vma->anon_vma) { 813 newflags &= ~VM_ACCOUNT; 814 } 815 816 vma = vma_modify_flags(vmi, *pprev, vma, start, end, newflags); 817 if (IS_ERR(vma)) { 818 error = PTR_ERR(vma); 819 goto fail; 820 } 821 822 *pprev = vma; 823 824 /* 825 * vm_flags and vm_page_prot are protected by the mmap_lock 826 * held in write mode. 827 */ 828 vma_start_write(vma); 829 vm_flags_reset_once(vma, newflags); 830 if (vma_wants_manual_pte_write_upgrade(vma)) 831 mm_cp_flags |= MM_CP_TRY_CHANGE_WRITABLE; 832 vma_set_page_prot(vma); 833 834 change_protection(tlb, vma, start, end, mm_cp_flags); 835 836 if ((oldflags & VM_ACCOUNT) && !(newflags & VM_ACCOUNT)) 837 vm_unacct_memory(nrpages); 838 839 /* 840 * Private VM_LOCKED VMA becoming writable: trigger COW to avoid major 841 * fault on access. 842 */ 843 if ((oldflags & (VM_WRITE | VM_SHARED | VM_LOCKED)) == VM_LOCKED && 844 (newflags & VM_WRITE)) { 845 populate_vma_page_range(vma, start, end, NULL); 846 } 847 848 vm_stat_account(mm, oldflags, -nrpages); 849 vm_stat_account(mm, newflags, nrpages); 850 perf_event_mmap(vma); 851 return 0; 852 853 fail: 854 vm_unacct_memory(charged); 855 return error; 856 } 857 858 /* 859 * pkey==-1 when doing a legacy mprotect() 860 */ 861 static int do_mprotect_pkey(unsigned long start, size_t len, 862 unsigned long prot, int pkey) 863 { 864 unsigned long nstart, end, tmp, reqprot; 865 struct vm_area_struct *vma, *prev; 866 int error; 867 const int grows = prot & (PROT_GROWSDOWN|PROT_GROWSUP); 868 const bool rier = (current->personality & READ_IMPLIES_EXEC) && 869 (prot & PROT_READ); 870 struct mmu_gather tlb; 871 struct vma_iterator vmi; 872 873 start = untagged_addr(start); 874 875 prot &= ~(PROT_GROWSDOWN|PROT_GROWSUP); 876 if (grows == (PROT_GROWSDOWN|PROT_GROWSUP)) /* can't be both */ 877 return -EINVAL; 878 879 if (start & ~PAGE_MASK) 880 return -EINVAL; 881 if (!len) 882 return 0; 883 len = PAGE_ALIGN(len); 884 end = start + len; 885 if (end <= start) 886 return -ENOMEM; 887 if (!arch_validate_prot(prot, start)) 888 return -EINVAL; 889 890 reqprot = prot; 891 892 if (mmap_write_lock_killable(current->mm)) 893 return -EINTR; 894 895 /* 896 * If userspace did not allocate the pkey, do not let 897 * them use it here. 898 */ 899 error = -EINVAL; 900 if ((pkey != -1) && !mm_pkey_is_allocated(current->mm, pkey)) 901 goto out; 902 903 vma_iter_init(&vmi, current->mm, start); 904 vma = vma_find(&vmi, end); 905 error = -ENOMEM; 906 if (!vma) 907 goto out; 908 909 if (unlikely(grows & PROT_GROWSDOWN)) { 910 if (vma->vm_start >= end) 911 goto out; 912 start = vma->vm_start; 913 error = -EINVAL; 914 if (!(vma->vm_flags & VM_GROWSDOWN)) 915 goto out; 916 } else { 917 if (vma->vm_start > start) 918 goto out; 919 if (unlikely(grows & PROT_GROWSUP)) { 920 end = vma->vm_end; 921 error = -EINVAL; 922 if (!(vma->vm_flags & VM_GROWSUP)) 923 goto out; 924 } 925 } 926 927 prev = vma_prev(&vmi); 928 if (start > vma->vm_start) 929 prev = vma; 930 931 tlb_gather_mmu(&tlb, current->mm); 932 nstart = start; 933 tmp = vma->vm_start; 934 for_each_vma_range(vmi, vma, end) { 935 vm_flags_t mask_off_old_flags; 936 vm_flags_t newflags; 937 int new_vma_pkey; 938 939 if (vma->vm_start != tmp) { 940 error = -ENOMEM; 941 break; 942 } 943 944 /* Does the application expect PROT_READ to imply PROT_EXEC */ 945 if (rier && (vma->vm_flags & VM_MAYEXEC)) 946 prot |= PROT_EXEC; 947 948 /* 949 * Each mprotect() call explicitly passes r/w/x permissions. 950 * If a permission is not passed to mprotect(), it must be 951 * cleared from the VMA. 952 */ 953 mask_off_old_flags = VM_ACCESS_FLAGS | VM_FLAGS_CLEAR; 954 955 new_vma_pkey = arch_override_mprotect_pkey(vma, prot, pkey); 956 newflags = calc_vm_prot_bits(prot, new_vma_pkey); 957 newflags |= (vma->vm_flags & ~mask_off_old_flags); 958 959 /* newflags >> 4 shift VM_MAY% in place of VM_% */ 960 if ((newflags & ~(newflags >> 4)) & VM_ACCESS_FLAGS) { 961 error = -EACCES; 962 break; 963 } 964 965 if (map_deny_write_exec(vma->vm_flags, newflags)) { 966 error = -EACCES; 967 break; 968 } 969 970 /* Allow architectures to sanity-check the new flags */ 971 if (!arch_validate_flags(newflags)) { 972 error = -EINVAL; 973 break; 974 } 975 976 error = security_file_mprotect(vma, reqprot, prot); 977 if (error) 978 break; 979 980 tmp = vma->vm_end; 981 if (tmp > end) 982 tmp = end; 983 984 if (vma->vm_ops && vma->vm_ops->mprotect) { 985 error = vma->vm_ops->mprotect(vma, nstart, tmp, newflags); 986 if (error) 987 break; 988 } 989 990 error = mprotect_fixup(&vmi, &tlb, vma, &prev, nstart, tmp, newflags); 991 if (error) 992 break; 993 994 tmp = vma_iter_end(&vmi); 995 nstart = tmp; 996 prot = reqprot; 997 } 998 tlb_finish_mmu(&tlb); 999 1000 if (!error && tmp < end) 1001 error = -ENOMEM; 1002 1003 out: 1004 mmap_write_unlock(current->mm); 1005 return error; 1006 } 1007 1008 SYSCALL_DEFINE3(mprotect, unsigned long, start, size_t, len, 1009 unsigned long, prot) 1010 { 1011 return do_mprotect_pkey(start, len, prot, -1); 1012 } 1013 1014 #ifdef CONFIG_ARCH_HAS_PKEYS 1015 1016 SYSCALL_DEFINE4(pkey_mprotect, unsigned long, start, size_t, len, 1017 unsigned long, prot, int, pkey) 1018 { 1019 return do_mprotect_pkey(start, len, prot, pkey); 1020 } 1021 1022 SYSCALL_DEFINE2(pkey_alloc, unsigned long, flags, unsigned long, init_val) 1023 { 1024 int pkey; 1025 int ret; 1026 1027 /* No flags supported yet. */ 1028 if (flags) 1029 return -EINVAL; 1030 /* check for unsupported init values */ 1031 if (init_val & ~PKEY_ACCESS_MASK) 1032 return -EINVAL; 1033 1034 mmap_write_lock(current->mm); 1035 pkey = mm_pkey_alloc(current->mm); 1036 1037 ret = -ENOSPC; 1038 if (pkey == -1) 1039 goto out; 1040 1041 ret = arch_set_user_pkey_access(current, pkey, init_val); 1042 if (ret) { 1043 mm_pkey_free(current->mm, pkey); 1044 goto out; 1045 } 1046 ret = pkey; 1047 out: 1048 mmap_write_unlock(current->mm); 1049 return ret; 1050 } 1051 1052 SYSCALL_DEFINE1(pkey_free, int, pkey) 1053 { 1054 int ret; 1055 1056 mmap_write_lock(current->mm); 1057 ret = mm_pkey_free(current->mm, pkey); 1058 mmap_write_unlock(current->mm); 1059 1060 /* 1061 * We could provide warnings or errors if any VMA still 1062 * has the pkey set here. 1063 */ 1064 return ret; 1065 } 1066 1067 #endif /* CONFIG_ARCH_HAS_PKEYS */ 1068