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 **foliop) 124 { 125 struct folio *folio = NULL; 126 bool ret = true; 127 bool toptier; 128 int nid; 129 130 /* Avoid TLB flush if possible */ 131 if (pte_protnone(oldpte)) 132 goto skip; 133 134 folio = vm_normal_folio(vma, addr, oldpte); 135 if (!folio) 136 goto skip; 137 138 if (folio_is_zone_device(folio) || folio_test_ksm(folio)) 139 goto skip; 140 141 /* Also skip shared copy-on-write pages */ 142 if (is_cow_mapping(vma->vm_flags) && 143 (folio_maybe_dma_pinned(folio) || folio_maybe_mapped_shared(folio))) 144 goto skip; 145 146 /* 147 * While migration can move some dirty pages, 148 * it cannot move them all from MIGRATE_ASYNC 149 * context. 150 */ 151 if (folio_is_file_lru(folio) && folio_test_dirty(folio)) 152 goto skip; 153 154 /* 155 * Don't mess with PTEs if page is already on the node 156 * a single-threaded process is running on. 157 */ 158 nid = folio_nid(folio); 159 if (target_node == nid) 160 goto skip; 161 162 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) && toptier) 169 goto skip; 170 171 ret = false; 172 if (folio_use_access_time(folio)) 173 folio_xchg_access_time(folio, jiffies_to_msecs(jiffies)); 174 175 skip: 176 *foliop = folio; 177 return ret; 178 } 179 180 /* Set nr_ptes number of ptes, starting from idx */ 181 static void prot_commit_flush_ptes(struct vm_area_struct *vma, unsigned long addr, 182 pte_t *ptep, pte_t oldpte, pte_t ptent, int nr_ptes, 183 int idx, bool set_write, struct mmu_gather *tlb) 184 { 185 /* 186 * Advance the position in the batch by idx; note that if idx > 0, 187 * then the nr_ptes passed here is <= batch size - idx. 188 */ 189 addr += idx * PAGE_SIZE; 190 ptep += idx; 191 oldpte = pte_advance_pfn(oldpte, idx); 192 ptent = pte_advance_pfn(ptent, idx); 193 194 if (set_write) 195 ptent = pte_mkwrite(ptent, vma); 196 197 modify_prot_commit_ptes(vma, addr, ptep, oldpte, ptent, nr_ptes); 198 if (pte_needs_flush(oldpte, ptent)) 199 tlb_flush_pte_range(tlb, addr, nr_ptes * PAGE_SIZE); 200 } 201 202 /* 203 * Get max length of consecutive ptes pointing to PageAnonExclusive() pages or 204 * !PageAnonExclusive() pages, starting from start_idx. Caller must enforce 205 * that the ptes point to consecutive pages of the same anon large folio. 206 */ 207 static int page_anon_exclusive_sub_batch(int start_idx, int max_len, 208 struct page *first_page, bool expected_anon_exclusive) 209 { 210 int idx; 211 212 for (idx = start_idx + 1; idx < start_idx + max_len; ++idx) { 213 if (expected_anon_exclusive != PageAnonExclusive(first_page + idx)) 214 break; 215 } 216 return idx - start_idx; 217 } 218 219 /* 220 * This function is a result of trying our very best to retain the 221 * "avoid the write-fault handler" optimization. In can_change_pte_writable(), 222 * if the vma is a private vma, and we cannot determine whether to change 223 * the pte to writable just from the vma and the pte, we then need to look 224 * at the actual page pointed to by the pte. Unfortunately, if we have a 225 * batch of ptes pointing to consecutive pages of the same anon large folio, 226 * the anon-exclusivity (or the negation) of the first page does not guarantee 227 * the anon-exclusivity (or the negation) of the other pages corresponding to 228 * the pte batch; hence in this case it is incorrect to decide to change or 229 * not change the ptes to writable just by using information from the first 230 * pte of the batch. Therefore, we must individually check all pages and 231 * retrieve sub-batches. 232 */ 233 static void commit_anon_folio_batch(struct vm_area_struct *vma, 234 struct folio *folio, unsigned long addr, pte_t *ptep, 235 pte_t oldpte, pte_t ptent, int nr_ptes, struct mmu_gather *tlb) 236 { 237 struct page *first_page = folio_page(folio, 0); 238 bool expected_anon_exclusive; 239 int sub_batch_idx = 0; 240 int len; 241 242 while (nr_ptes) { 243 expected_anon_exclusive = PageAnonExclusive(first_page + sub_batch_idx); 244 len = page_anon_exclusive_sub_batch(sub_batch_idx, nr_ptes, 245 first_page, expected_anon_exclusive); 246 prot_commit_flush_ptes(vma, addr, ptep, oldpte, ptent, len, 247 sub_batch_idx, expected_anon_exclusive, tlb); 248 sub_batch_idx += len; 249 nr_ptes -= len; 250 } 251 } 252 253 static void set_write_prot_commit_flush_ptes(struct vm_area_struct *vma, 254 struct folio *folio, unsigned long addr, pte_t *ptep, 255 pte_t oldpte, pte_t ptent, int nr_ptes, struct mmu_gather *tlb) 256 { 257 bool set_write; 258 259 if (vma->vm_flags & VM_SHARED) { 260 set_write = can_change_shared_pte_writable(vma, ptent); 261 prot_commit_flush_ptes(vma, addr, ptep, oldpte, ptent, nr_ptes, 262 /* idx = */ 0, set_write, tlb); 263 return; 264 } 265 266 set_write = maybe_change_pte_writable(vma, ptent) && 267 (folio && folio_test_anon(folio)); 268 if (!set_write) { 269 prot_commit_flush_ptes(vma, addr, ptep, oldpte, ptent, nr_ptes, 270 /* idx = */ 0, set_write, tlb); 271 return; 272 } 273 commit_anon_folio_batch(vma, folio, addr, ptep, oldpte, ptent, nr_ptes, tlb); 274 } 275 276 static long change_pte_range(struct mmu_gather *tlb, 277 struct vm_area_struct *vma, pmd_t *pmd, unsigned long addr, 278 unsigned long end, pgprot_t newprot, unsigned long cp_flags) 279 { 280 pte_t *pte, oldpte; 281 spinlock_t *ptl; 282 long pages = 0; 283 int target_node = NUMA_NO_NODE; 284 bool prot_numa = cp_flags & MM_CP_PROT_NUMA; 285 bool uffd_wp = cp_flags & MM_CP_UFFD_WP; 286 bool uffd_wp_resolve = cp_flags & MM_CP_UFFD_WP_RESOLVE; 287 int nr_ptes; 288 289 tlb_change_page_size(tlb, PAGE_SIZE); 290 pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); 291 if (!pte) 292 return -EAGAIN; 293 294 /* Get target node for single threaded private VMAs */ 295 if (prot_numa && !(vma->vm_flags & VM_SHARED) && 296 atomic_read(&vma->vm_mm->mm_users) == 1) 297 target_node = numa_node_id(); 298 299 flush_tlb_batched_pending(vma->vm_mm); 300 arch_enter_lazy_mmu_mode(); 301 do { 302 nr_ptes = 1; 303 oldpte = ptep_get(pte); 304 if (pte_present(oldpte)) { 305 const fpb_t flags = FPB_RESPECT_SOFT_DIRTY | FPB_RESPECT_WRITE; 306 int max_nr_ptes = (end - addr) >> PAGE_SHIFT; 307 struct folio *folio = NULL; 308 pte_t ptent; 309 310 /* 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 if (!folio) 327 folio = vm_normal_folio(vma, addr, oldpte); 328 329 nr_ptes = mprotect_folio_pte_batch(folio, pte, oldpte, max_nr_ptes, flags); 330 331 oldpte = modify_prot_start_ptes(vma, addr, pte, nr_ptes); 332 ptent = pte_modify(oldpte, newprot); 333 334 if (uffd_wp) 335 ptent = pte_mkuffd_wp(ptent); 336 else if (uffd_wp_resolve) 337 ptent = pte_clear_uffd_wp(ptent); 338 339 /* 340 * In some writable, shared mappings, we might want 341 * to catch actual write access -- see 342 * vma_wants_writenotify(). 343 * 344 * In all writable, private mappings, we have to 345 * properly handle COW. 346 * 347 * In both cases, we can sometimes still change PTEs 348 * writable and avoid the write-fault handler, for 349 * example, if a PTE is already dirty and no other 350 * COW or special handling is required. 351 */ 352 if ((cp_flags & MM_CP_TRY_CHANGE_WRITABLE) && 353 !pte_write(ptent)) 354 set_write_prot_commit_flush_ptes(vma, folio, 355 addr, pte, oldpte, ptent, nr_ptes, tlb); 356 else 357 prot_commit_flush_ptes(vma, addr, pte, oldpte, ptent, 358 nr_ptes, /* idx = */ 0, /* set_write = */ false, tlb); 359 pages += nr_ptes; 360 } else if (is_swap_pte(oldpte)) { 361 swp_entry_t entry = pte_to_swp_entry(oldpte); 362 pte_t newpte; 363 364 if (is_writable_migration_entry(entry)) { 365 struct folio *folio = pfn_swap_entry_folio(entry); 366 367 /* 368 * A protection check is difficult so 369 * just be safe and disable write 370 */ 371 if (folio_test_anon(folio)) 372 entry = make_readable_exclusive_migration_entry( 373 swp_offset(entry)); 374 else 375 entry = make_readable_migration_entry(swp_offset(entry)); 376 newpte = swp_entry_to_pte(entry); 377 if (pte_swp_soft_dirty(oldpte)) 378 newpte = pte_swp_mksoft_dirty(newpte); 379 } else if (is_writable_device_private_entry(entry)) { 380 /* 381 * We do not preserve soft-dirtiness. See 382 * copy_nonpresent_pte() for explanation. 383 */ 384 entry = make_readable_device_private_entry( 385 swp_offset(entry)); 386 newpte = swp_entry_to_pte(entry); 387 if (pte_swp_uffd_wp(oldpte)) 388 newpte = pte_swp_mkuffd_wp(newpte); 389 } else if (is_pte_marker_entry(entry)) { 390 /* 391 * Ignore error swap entries unconditionally, 392 * because any access should sigbus/sigsegv 393 * anyway. 394 */ 395 if (is_poisoned_swp_entry(entry) || 396 is_guard_swp_entry(entry)) 397 continue; 398 /* 399 * If this is uffd-wp pte marker and we'd like 400 * to unprotect it, drop it; the next page 401 * fault will trigger without uffd trapping. 402 */ 403 if (uffd_wp_resolve) { 404 pte_clear(vma->vm_mm, addr, pte); 405 pages++; 406 } 407 continue; 408 } else { 409 newpte = oldpte; 410 } 411 412 if (uffd_wp) 413 newpte = pte_swp_mkuffd_wp(newpte); 414 else if (uffd_wp_resolve) 415 newpte = pte_swp_clear_uffd_wp(newpte); 416 417 if (!pte_same(oldpte, newpte)) { 418 set_pte_at(vma->vm_mm, addr, pte, newpte); 419 pages++; 420 } 421 } else { 422 /* It must be an none page, or what else?.. */ 423 WARN_ON_ONCE(!pte_none(oldpte)); 424 425 /* 426 * Nobody plays with any none ptes besides 427 * userfaultfd when applying the protections. 428 */ 429 if (likely(!uffd_wp)) 430 continue; 431 432 if (userfaultfd_wp_use_markers(vma)) { 433 /* 434 * For file-backed mem, we need to be able to 435 * wr-protect a none pte, because even if the 436 * pte is none, the page/swap cache could 437 * exist. Doing that by install a marker. 438 */ 439 set_pte_at(vma->vm_mm, addr, pte, 440 make_pte_marker(PTE_MARKER_UFFD_WP)); 441 pages++; 442 } 443 } 444 } while (pte += nr_ptes, addr += nr_ptes * PAGE_SIZE, addr != end); 445 arch_leave_lazy_mmu_mode(); 446 pte_unmap_unlock(pte - 1, ptl); 447 448 return pages; 449 } 450 451 /* 452 * Return true if we want to split THPs into PTE mappings in change 453 * protection procedure, false otherwise. 454 */ 455 static inline bool 456 pgtable_split_needed(struct vm_area_struct *vma, unsigned long cp_flags) 457 { 458 /* 459 * pte markers only resides in pte level, if we need pte markers, 460 * we need to split. For example, we cannot wr-protect a file thp 461 * (e.g. 2M shmem) because file thp is handled differently when 462 * split by erasing the pmd so far. 463 */ 464 return (cp_flags & MM_CP_UFFD_WP) && !vma_is_anonymous(vma); 465 } 466 467 /* 468 * Return true if we want to populate pgtables in change protection 469 * procedure, false otherwise 470 */ 471 static inline bool 472 pgtable_populate_needed(struct vm_area_struct *vma, unsigned long cp_flags) 473 { 474 /* If not within ioctl(UFFDIO_WRITEPROTECT), then don't bother */ 475 if (!(cp_flags & MM_CP_UFFD_WP)) 476 return false; 477 478 /* Populate if the userfaultfd mode requires pte markers */ 479 return userfaultfd_wp_use_markers(vma); 480 } 481 482 /* 483 * Populate the pgtable underneath for whatever reason if requested. 484 * When {pte|pmd|...}_alloc() failed we treat it the same way as pgtable 485 * allocation failures during page faults by kicking OOM and returning 486 * error. 487 */ 488 #define change_pmd_prepare(vma, pmd, cp_flags) \ 489 ({ \ 490 long err = 0; \ 491 if (unlikely(pgtable_populate_needed(vma, cp_flags))) { \ 492 if (pte_alloc(vma->vm_mm, pmd)) \ 493 err = -ENOMEM; \ 494 } \ 495 err; \ 496 }) 497 498 /* 499 * This is the general pud/p4d/pgd version of change_pmd_prepare(). We need to 500 * have separate change_pmd_prepare() because pte_alloc() returns 0 on success, 501 * while {pmd|pud|p4d}_alloc() returns the valid pointer on success. 502 */ 503 #define change_prepare(vma, high, low, addr, cp_flags) \ 504 ({ \ 505 long err = 0; \ 506 if (unlikely(pgtable_populate_needed(vma, cp_flags))) { \ 507 low##_t *p = low##_alloc(vma->vm_mm, high, addr); \ 508 if (p == NULL) \ 509 err = -ENOMEM; \ 510 } \ 511 err; \ 512 }) 513 514 static inline long change_pmd_range(struct mmu_gather *tlb, 515 struct vm_area_struct *vma, pud_t *pud, unsigned long addr, 516 unsigned long end, pgprot_t newprot, unsigned long cp_flags) 517 { 518 pmd_t *pmd; 519 unsigned long next; 520 long pages = 0; 521 unsigned long nr_huge_updates = 0; 522 523 pmd = pmd_offset(pud, addr); 524 do { 525 long ret; 526 pmd_t _pmd; 527 again: 528 next = pmd_addr_end(addr, end); 529 530 ret = change_pmd_prepare(vma, pmd, cp_flags); 531 if (ret) { 532 pages = ret; 533 break; 534 } 535 536 if (pmd_none(*pmd)) 537 goto next; 538 539 _pmd = pmdp_get_lockless(pmd); 540 if (is_swap_pmd(_pmd) || pmd_trans_huge(_pmd)) { 541 if ((next - addr != HPAGE_PMD_SIZE) || 542 pgtable_split_needed(vma, cp_flags)) { 543 __split_huge_pmd(vma, pmd, addr, false); 544 /* 545 * For file-backed, the pmd could have been 546 * cleared; make sure pmd populated if 547 * necessary, then fall-through to pte level. 548 */ 549 ret = change_pmd_prepare(vma, pmd, cp_flags); 550 if (ret) { 551 pages = ret; 552 break; 553 } 554 } else { 555 ret = change_huge_pmd(tlb, vma, pmd, 556 addr, newprot, cp_flags); 557 if (ret) { 558 if (ret == HPAGE_PMD_NR) { 559 pages += HPAGE_PMD_NR; 560 nr_huge_updates++; 561 } 562 563 /* huge pmd was handled */ 564 goto next; 565 } 566 } 567 /* fall through, the trans huge pmd just split */ 568 } 569 570 ret = change_pte_range(tlb, vma, pmd, addr, next, newprot, 571 cp_flags); 572 if (ret < 0) 573 goto again; 574 pages += ret; 575 next: 576 cond_resched(); 577 } while (pmd++, addr = next, addr != end); 578 579 if (nr_huge_updates) 580 count_vm_numa_events(NUMA_HUGE_PTE_UPDATES, nr_huge_updates); 581 return pages; 582 } 583 584 static inline long change_pud_range(struct mmu_gather *tlb, 585 struct vm_area_struct *vma, p4d_t *p4d, unsigned long addr, 586 unsigned long end, pgprot_t newprot, unsigned long cp_flags) 587 { 588 struct mmu_notifier_range range; 589 pud_t *pudp, pud; 590 unsigned long next; 591 long pages = 0, ret; 592 593 range.start = 0; 594 595 pudp = pud_offset(p4d, addr); 596 do { 597 again: 598 next = pud_addr_end(addr, end); 599 ret = change_prepare(vma, pudp, pmd, addr, cp_flags); 600 if (ret) { 601 pages = ret; 602 break; 603 } 604 605 pud = READ_ONCE(*pudp); 606 if (pud_none(pud)) 607 continue; 608 609 if (!range.start) { 610 mmu_notifier_range_init(&range, 611 MMU_NOTIFY_PROTECTION_VMA, 0, 612 vma->vm_mm, addr, end); 613 mmu_notifier_invalidate_range_start(&range); 614 } 615 616 if (pud_leaf(pud)) { 617 if ((next - addr != PUD_SIZE) || 618 pgtable_split_needed(vma, cp_flags)) { 619 __split_huge_pud(vma, pudp, addr); 620 goto again; 621 } else { 622 ret = change_huge_pud(tlb, vma, pudp, 623 addr, newprot, cp_flags); 624 if (ret == 0) 625 goto again; 626 /* huge pud was handled */ 627 if (ret == HPAGE_PUD_NR) 628 pages += HPAGE_PUD_NR; 629 continue; 630 } 631 } 632 633 pages += change_pmd_range(tlb, vma, pudp, addr, next, newprot, 634 cp_flags); 635 } while (pudp++, addr = next, addr != end); 636 637 if (range.start) 638 mmu_notifier_invalidate_range_end(&range); 639 640 return pages; 641 } 642 643 static inline long change_p4d_range(struct mmu_gather *tlb, 644 struct vm_area_struct *vma, pgd_t *pgd, unsigned long addr, 645 unsigned long end, pgprot_t newprot, unsigned long cp_flags) 646 { 647 p4d_t *p4d; 648 unsigned long next; 649 long pages = 0, ret; 650 651 p4d = p4d_offset(pgd, addr); 652 do { 653 next = p4d_addr_end(addr, end); 654 ret = change_prepare(vma, p4d, pud, addr, cp_flags); 655 if (ret) 656 return ret; 657 if (p4d_none_or_clear_bad(p4d)) 658 continue; 659 pages += change_pud_range(tlb, vma, p4d, addr, next, newprot, 660 cp_flags); 661 } while (p4d++, addr = next, addr != end); 662 663 return pages; 664 } 665 666 static long change_protection_range(struct mmu_gather *tlb, 667 struct vm_area_struct *vma, unsigned long addr, 668 unsigned long end, pgprot_t newprot, unsigned long cp_flags) 669 { 670 struct mm_struct *mm = vma->vm_mm; 671 pgd_t *pgd; 672 unsigned long next; 673 long pages = 0, ret; 674 675 BUG_ON(addr >= end); 676 pgd = pgd_offset(mm, addr); 677 tlb_start_vma(tlb, vma); 678 do { 679 next = pgd_addr_end(addr, end); 680 ret = change_prepare(vma, pgd, p4d, addr, cp_flags); 681 if (ret) { 682 pages = ret; 683 break; 684 } 685 if (pgd_none_or_clear_bad(pgd)) 686 continue; 687 pages += change_p4d_range(tlb, vma, pgd, addr, next, newprot, 688 cp_flags); 689 } while (pgd++, addr = next, addr != end); 690 691 tlb_end_vma(tlb, vma); 692 693 return pages; 694 } 695 696 long change_protection(struct mmu_gather *tlb, 697 struct vm_area_struct *vma, unsigned long start, 698 unsigned long end, unsigned long cp_flags) 699 { 700 pgprot_t newprot = vma->vm_page_prot; 701 long pages; 702 703 BUG_ON((cp_flags & MM_CP_UFFD_WP_ALL) == MM_CP_UFFD_WP_ALL); 704 705 #ifdef CONFIG_NUMA_BALANCING 706 /* 707 * Ordinary protection updates (mprotect, uffd-wp, softdirty tracking) 708 * are expected to reflect their requirements via VMA flags such that 709 * vma_set_page_prot() will adjust vma->vm_page_prot accordingly. 710 */ 711 if (cp_flags & MM_CP_PROT_NUMA) 712 newprot = PAGE_NONE; 713 #else 714 WARN_ON_ONCE(cp_flags & MM_CP_PROT_NUMA); 715 #endif 716 717 if (is_vm_hugetlb_page(vma)) 718 pages = hugetlb_change_protection(vma, start, end, newprot, 719 cp_flags); 720 else 721 pages = change_protection_range(tlb, vma, start, end, newprot, 722 cp_flags); 723 724 return pages; 725 } 726 727 static int prot_none_pte_entry(pte_t *pte, unsigned long addr, 728 unsigned long next, struct mm_walk *walk) 729 { 730 return pfn_modify_allowed(pte_pfn(ptep_get(pte)), 731 *(pgprot_t *)(walk->private)) ? 732 0 : -EACCES; 733 } 734 735 static int prot_none_hugetlb_entry(pte_t *pte, unsigned long hmask, 736 unsigned long addr, unsigned long next, 737 struct mm_walk *walk) 738 { 739 return pfn_modify_allowed(pte_pfn(ptep_get(pte)), 740 *(pgprot_t *)(walk->private)) ? 741 0 : -EACCES; 742 } 743 744 static int prot_none_test(unsigned long addr, unsigned long next, 745 struct mm_walk *walk) 746 { 747 return 0; 748 } 749 750 static const struct mm_walk_ops prot_none_walk_ops = { 751 .pte_entry = prot_none_pte_entry, 752 .hugetlb_entry = prot_none_hugetlb_entry, 753 .test_walk = prot_none_test, 754 .walk_lock = PGWALK_WRLOCK, 755 }; 756 757 int 758 mprotect_fixup(struct vma_iterator *vmi, struct mmu_gather *tlb, 759 struct vm_area_struct *vma, struct vm_area_struct **pprev, 760 unsigned long start, unsigned long end, vm_flags_t newflags) 761 { 762 struct mm_struct *mm = vma->vm_mm; 763 vm_flags_t oldflags = READ_ONCE(vma->vm_flags); 764 long nrpages = (end - start) >> PAGE_SHIFT; 765 unsigned int mm_cp_flags = 0; 766 unsigned long charged = 0; 767 int error; 768 769 if (!can_modify_vma(vma)) 770 return -EPERM; 771 772 if (newflags == oldflags) { 773 *pprev = vma; 774 return 0; 775 } 776 777 /* 778 * Do PROT_NONE PFN permission checks here when we can still 779 * bail out without undoing a lot of state. This is a rather 780 * uncommon case, so doesn't need to be very optimized. 781 */ 782 if (arch_has_pfn_modify_check() && 783 (oldflags & (VM_PFNMAP|VM_MIXEDMAP)) && 784 (newflags & VM_ACCESS_FLAGS) == 0) { 785 pgprot_t new_pgprot = vm_get_page_prot(newflags); 786 787 error = walk_page_range(current->mm, start, end, 788 &prot_none_walk_ops, &new_pgprot); 789 if (error) 790 return error; 791 } 792 793 /* 794 * If we make a private mapping writable we increase our commit; 795 * but (without finer accounting) cannot reduce our commit if we 796 * make it unwritable again except in the anonymous case where no 797 * anon_vma has yet to be assigned. 798 * 799 * hugetlb mapping were accounted for even if read-only so there is 800 * no need to account for them here. 801 */ 802 if (newflags & VM_WRITE) { 803 /* Check space limits when area turns into data. */ 804 if (!may_expand_vm(mm, newflags, nrpages) && 805 may_expand_vm(mm, oldflags, nrpages)) 806 return -ENOMEM; 807 if (!(oldflags & (VM_ACCOUNT|VM_WRITE|VM_HUGETLB| 808 VM_SHARED|VM_NORESERVE))) { 809 charged = nrpages; 810 if (security_vm_enough_memory_mm(mm, charged)) 811 return -ENOMEM; 812 newflags |= VM_ACCOUNT; 813 } 814 } else if ((oldflags & VM_ACCOUNT) && vma_is_anonymous(vma) && 815 !vma->anon_vma) { 816 newflags &= ~VM_ACCOUNT; 817 } 818 819 vma = vma_modify_flags(vmi, *pprev, vma, start, end, newflags); 820 if (IS_ERR(vma)) { 821 error = PTR_ERR(vma); 822 goto fail; 823 } 824 825 *pprev = vma; 826 827 /* 828 * vm_flags and vm_page_prot are protected by the mmap_lock 829 * held in write mode. 830 */ 831 vma_start_write(vma); 832 vm_flags_reset_once(vma, newflags); 833 if (vma_wants_manual_pte_write_upgrade(vma)) 834 mm_cp_flags |= MM_CP_TRY_CHANGE_WRITABLE; 835 vma_set_page_prot(vma); 836 837 change_protection(tlb, vma, start, end, mm_cp_flags); 838 839 if ((oldflags & VM_ACCOUNT) && !(newflags & VM_ACCOUNT)) 840 vm_unacct_memory(nrpages); 841 842 /* 843 * Private VM_LOCKED VMA becoming writable: trigger COW to avoid major 844 * fault on access. 845 */ 846 if ((oldflags & (VM_WRITE | VM_SHARED | VM_LOCKED)) == VM_LOCKED && 847 (newflags & VM_WRITE)) { 848 populate_vma_page_range(vma, start, end, NULL); 849 } 850 851 vm_stat_account(mm, oldflags, -nrpages); 852 vm_stat_account(mm, newflags, nrpages); 853 perf_event_mmap(vma); 854 return 0; 855 856 fail: 857 vm_unacct_memory(charged); 858 return error; 859 } 860 861 /* 862 * pkey==-1 when doing a legacy mprotect() 863 */ 864 static int do_mprotect_pkey(unsigned long start, size_t len, 865 unsigned long prot, int pkey) 866 { 867 unsigned long nstart, end, tmp, reqprot; 868 struct vm_area_struct *vma, *prev; 869 int error; 870 const int grows = prot & (PROT_GROWSDOWN|PROT_GROWSUP); 871 const bool rier = (current->personality & READ_IMPLIES_EXEC) && 872 (prot & PROT_READ); 873 struct mmu_gather tlb; 874 struct vma_iterator vmi; 875 876 start = untagged_addr(start); 877 878 prot &= ~(PROT_GROWSDOWN|PROT_GROWSUP); 879 if (grows == (PROT_GROWSDOWN|PROT_GROWSUP)) /* can't be both */ 880 return -EINVAL; 881 882 if (start & ~PAGE_MASK) 883 return -EINVAL; 884 if (!len) 885 return 0; 886 len = PAGE_ALIGN(len); 887 end = start + len; 888 if (end <= start) 889 return -ENOMEM; 890 if (!arch_validate_prot(prot, start)) 891 return -EINVAL; 892 893 reqprot = prot; 894 895 if (mmap_write_lock_killable(current->mm)) 896 return -EINTR; 897 898 /* 899 * If userspace did not allocate the pkey, do not let 900 * them use it here. 901 */ 902 error = -EINVAL; 903 if ((pkey != -1) && !mm_pkey_is_allocated(current->mm, pkey)) 904 goto out; 905 906 vma_iter_init(&vmi, current->mm, start); 907 vma = vma_find(&vmi, end); 908 error = -ENOMEM; 909 if (!vma) 910 goto out; 911 912 if (unlikely(grows & PROT_GROWSDOWN)) { 913 if (vma->vm_start >= end) 914 goto out; 915 start = vma->vm_start; 916 error = -EINVAL; 917 if (!(vma->vm_flags & VM_GROWSDOWN)) 918 goto out; 919 } else { 920 if (vma->vm_start > start) 921 goto out; 922 if (unlikely(grows & PROT_GROWSUP)) { 923 end = vma->vm_end; 924 error = -EINVAL; 925 if (!(vma->vm_flags & VM_GROWSUP)) 926 goto out; 927 } 928 } 929 930 prev = vma_prev(&vmi); 931 if (start > vma->vm_start) 932 prev = vma; 933 934 tlb_gather_mmu(&tlb, current->mm); 935 nstart = start; 936 tmp = vma->vm_start; 937 for_each_vma_range(vmi, vma, end) { 938 vm_flags_t mask_off_old_flags; 939 vm_flags_t newflags; 940 int new_vma_pkey; 941 942 if (vma->vm_start != tmp) { 943 error = -ENOMEM; 944 break; 945 } 946 947 /* Does the application expect PROT_READ to imply PROT_EXEC */ 948 if (rier && (vma->vm_flags & VM_MAYEXEC)) 949 prot |= PROT_EXEC; 950 951 /* 952 * Each mprotect() call explicitly passes r/w/x permissions. 953 * If a permission is not passed to mprotect(), it must be 954 * cleared from the VMA. 955 */ 956 mask_off_old_flags = VM_ACCESS_FLAGS | VM_FLAGS_CLEAR; 957 958 new_vma_pkey = arch_override_mprotect_pkey(vma, prot, pkey); 959 newflags = calc_vm_prot_bits(prot, new_vma_pkey); 960 newflags |= (vma->vm_flags & ~mask_off_old_flags); 961 962 /* newflags >> 4 shift VM_MAY% in place of VM_% */ 963 if ((newflags & ~(newflags >> 4)) & VM_ACCESS_FLAGS) { 964 error = -EACCES; 965 break; 966 } 967 968 if (map_deny_write_exec(vma->vm_flags, newflags)) { 969 error = -EACCES; 970 break; 971 } 972 973 /* Allow architectures to sanity-check the new flags */ 974 if (!arch_validate_flags(newflags)) { 975 error = -EINVAL; 976 break; 977 } 978 979 error = security_file_mprotect(vma, reqprot, prot); 980 if (error) 981 break; 982 983 tmp = vma->vm_end; 984 if (tmp > end) 985 tmp = end; 986 987 if (vma->vm_ops && vma->vm_ops->mprotect) { 988 error = vma->vm_ops->mprotect(vma, nstart, tmp, newflags); 989 if (error) 990 break; 991 } 992 993 error = mprotect_fixup(&vmi, &tlb, vma, &prev, nstart, tmp, newflags); 994 if (error) 995 break; 996 997 tmp = vma_iter_end(&vmi); 998 nstart = tmp; 999 prot = reqprot; 1000 } 1001 tlb_finish_mmu(&tlb); 1002 1003 if (!error && tmp < end) 1004 error = -ENOMEM; 1005 1006 out: 1007 mmap_write_unlock(current->mm); 1008 return error; 1009 } 1010 1011 SYSCALL_DEFINE3(mprotect, unsigned long, start, size_t, len, 1012 unsigned long, prot) 1013 { 1014 return do_mprotect_pkey(start, len, prot, -1); 1015 } 1016 1017 #ifdef CONFIG_ARCH_HAS_PKEYS 1018 1019 SYSCALL_DEFINE4(pkey_mprotect, unsigned long, start, size_t, len, 1020 unsigned long, prot, int, pkey) 1021 { 1022 return do_mprotect_pkey(start, len, prot, pkey); 1023 } 1024 1025 SYSCALL_DEFINE2(pkey_alloc, unsigned long, flags, unsigned long, init_val) 1026 { 1027 int pkey; 1028 int ret; 1029 1030 /* No flags supported yet. */ 1031 if (flags) 1032 return -EINVAL; 1033 /* check for unsupported init values */ 1034 if (init_val & ~PKEY_ACCESS_MASK) 1035 return -EINVAL; 1036 1037 mmap_write_lock(current->mm); 1038 pkey = mm_pkey_alloc(current->mm); 1039 1040 ret = -ENOSPC; 1041 if (pkey == -1) 1042 goto out; 1043 1044 ret = arch_set_user_pkey_access(current, pkey, init_val); 1045 if (ret) { 1046 mm_pkey_free(current->mm, pkey); 1047 goto out; 1048 } 1049 ret = pkey; 1050 out: 1051 mmap_write_unlock(current->mm); 1052 return ret; 1053 } 1054 1055 SYSCALL_DEFINE1(pkey_free, int, pkey) 1056 { 1057 int ret; 1058 1059 mmap_write_lock(current->mm); 1060 ret = mm_pkey_free(current->mm, pkey); 1061 mmap_write_unlock(current->mm); 1062 1063 /* 1064 * We could provide warnings or errors if any VMA still 1065 * has the pkey set here. 1066 */ 1067 return ret; 1068 } 1069 1070 #endif /* CONFIG_ARCH_HAS_PKEYS */ 1071