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