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 (is_swap_pte(oldpte)) { 301 swp_entry_t entry = pte_to_swp_entry(oldpte); 302 pte_t newpte; 303 304 if (is_writable_migration_entry(entry)) { 305 struct folio *folio = pfn_swap_entry_folio(entry); 306 307 /* 308 * A protection check is difficult so 309 * just be safe and disable write 310 */ 311 if (folio_test_anon(folio)) 312 entry = make_readable_exclusive_migration_entry( 313 swp_offset(entry)); 314 else 315 entry = make_readable_migration_entry(swp_offset(entry)); 316 newpte = swp_entry_to_pte(entry); 317 if (pte_swp_soft_dirty(oldpte)) 318 newpte = pte_swp_mksoft_dirty(newpte); 319 } else if (is_writable_device_private_entry(entry)) { 320 /* 321 * We do not preserve soft-dirtiness. See 322 * copy_nonpresent_pte() for explanation. 323 */ 324 entry = make_readable_device_private_entry( 325 swp_offset(entry)); 326 newpte = swp_entry_to_pte(entry); 327 if (pte_swp_uffd_wp(oldpte)) 328 newpte = pte_swp_mkuffd_wp(newpte); 329 } else if (is_pte_marker_entry(entry)) { 330 /* 331 * Ignore error swap entries unconditionally, 332 * because any access should sigbus/sigsegv 333 * anyway. 334 */ 335 if (is_poisoned_swp_entry(entry) || 336 is_guard_swp_entry(entry)) 337 continue; 338 /* 339 * If this is uffd-wp pte marker and we'd like 340 * to unprotect it, drop it; the next page 341 * fault will trigger without uffd trapping. 342 */ 343 if (uffd_wp_resolve) { 344 pte_clear(vma->vm_mm, addr, pte); 345 pages++; 346 } 347 continue; 348 } else { 349 newpte = oldpte; 350 } 351 352 if (uffd_wp) 353 newpte = pte_swp_mkuffd_wp(newpte); 354 else if (uffd_wp_resolve) 355 newpte = pte_swp_clear_uffd_wp(newpte); 356 357 if (!pte_same(oldpte, newpte)) { 358 set_pte_at(vma->vm_mm, addr, pte, newpte); 359 pages++; 360 } 361 } else { 362 /* It must be an none page, or what else?.. */ 363 WARN_ON_ONCE(!pte_none(oldpte)); 364 365 /* 366 * Nobody plays with any none ptes besides 367 * userfaultfd when applying the protections. 368 */ 369 if (likely(!uffd_wp)) 370 continue; 371 372 if (userfaultfd_wp_use_markers(vma)) { 373 /* 374 * For file-backed mem, we need to be able to 375 * wr-protect a none pte, because even if the 376 * pte is none, the page/swap cache could 377 * exist. Doing that by install a marker. 378 */ 379 set_pte_at(vma->vm_mm, addr, pte, 380 make_pte_marker(PTE_MARKER_UFFD_WP)); 381 pages++; 382 } 383 } 384 } while (pte += nr_ptes, addr += nr_ptes * PAGE_SIZE, addr != end); 385 arch_leave_lazy_mmu_mode(); 386 pte_unmap_unlock(pte - 1, ptl); 387 388 return pages; 389 } 390 391 /* 392 * Return true if we want to split THPs into PTE mappings in change 393 * protection procedure, false otherwise. 394 */ 395 static inline bool 396 pgtable_split_needed(struct vm_area_struct *vma, unsigned long cp_flags) 397 { 398 /* 399 * pte markers only resides in pte level, if we need pte markers, 400 * we need to split. For example, we cannot wr-protect a file thp 401 * (e.g. 2M shmem) because file thp is handled differently when 402 * split by erasing the pmd so far. 403 */ 404 return (cp_flags & MM_CP_UFFD_WP) && !vma_is_anonymous(vma); 405 } 406 407 /* 408 * Return true if we want to populate pgtables in change protection 409 * procedure, false otherwise 410 */ 411 static inline bool 412 pgtable_populate_needed(struct vm_area_struct *vma, unsigned long cp_flags) 413 { 414 /* If not within ioctl(UFFDIO_WRITEPROTECT), then don't bother */ 415 if (!(cp_flags & MM_CP_UFFD_WP)) 416 return false; 417 418 /* Populate if the userfaultfd mode requires pte markers */ 419 return userfaultfd_wp_use_markers(vma); 420 } 421 422 /* 423 * Populate the pgtable underneath for whatever reason if requested. 424 * When {pte|pmd|...}_alloc() failed we treat it the same way as pgtable 425 * allocation failures during page faults by kicking OOM and returning 426 * error. 427 */ 428 #define change_pmd_prepare(vma, pmd, cp_flags) \ 429 ({ \ 430 long err = 0; \ 431 if (unlikely(pgtable_populate_needed(vma, cp_flags))) { \ 432 if (pte_alloc(vma->vm_mm, pmd)) \ 433 err = -ENOMEM; \ 434 } \ 435 err; \ 436 }) 437 438 /* 439 * This is the general pud/p4d/pgd version of change_pmd_prepare(). We need to 440 * have separate change_pmd_prepare() because pte_alloc() returns 0 on success, 441 * while {pmd|pud|p4d}_alloc() returns the valid pointer on success. 442 */ 443 #define change_prepare(vma, high, low, addr, cp_flags) \ 444 ({ \ 445 long err = 0; \ 446 if (unlikely(pgtable_populate_needed(vma, cp_flags))) { \ 447 low##_t *p = low##_alloc(vma->vm_mm, high, addr); \ 448 if (p == NULL) \ 449 err = -ENOMEM; \ 450 } \ 451 err; \ 452 }) 453 454 static inline long change_pmd_range(struct mmu_gather *tlb, 455 struct vm_area_struct *vma, pud_t *pud, unsigned long addr, 456 unsigned long end, pgprot_t newprot, unsigned long cp_flags) 457 { 458 pmd_t *pmd; 459 unsigned long next; 460 long pages = 0; 461 unsigned long nr_huge_updates = 0; 462 463 pmd = pmd_offset(pud, addr); 464 do { 465 long ret; 466 pmd_t _pmd; 467 again: 468 next = pmd_addr_end(addr, end); 469 470 ret = change_pmd_prepare(vma, pmd, cp_flags); 471 if (ret) { 472 pages = ret; 473 break; 474 } 475 476 if (pmd_none(*pmd)) 477 goto next; 478 479 _pmd = pmdp_get_lockless(pmd); 480 if (is_swap_pmd(_pmd) || pmd_trans_huge(_pmd)) { 481 if ((next - addr != HPAGE_PMD_SIZE) || 482 pgtable_split_needed(vma, cp_flags)) { 483 __split_huge_pmd(vma, pmd, addr, false); 484 /* 485 * For file-backed, the pmd could have been 486 * cleared; make sure pmd populated if 487 * necessary, then fall-through to pte level. 488 */ 489 ret = change_pmd_prepare(vma, pmd, cp_flags); 490 if (ret) { 491 pages = ret; 492 break; 493 } 494 } else { 495 ret = change_huge_pmd(tlb, vma, pmd, 496 addr, newprot, cp_flags); 497 if (ret) { 498 if (ret == HPAGE_PMD_NR) { 499 pages += HPAGE_PMD_NR; 500 nr_huge_updates++; 501 } 502 503 /* huge pmd was handled */ 504 goto next; 505 } 506 } 507 /* fall through, the trans huge pmd just split */ 508 } 509 510 ret = change_pte_range(tlb, vma, pmd, addr, next, newprot, 511 cp_flags); 512 if (ret < 0) 513 goto again; 514 pages += ret; 515 next: 516 cond_resched(); 517 } while (pmd++, addr = next, addr != end); 518 519 if (nr_huge_updates) 520 count_vm_numa_events(NUMA_HUGE_PTE_UPDATES, nr_huge_updates); 521 return pages; 522 } 523 524 static inline long change_pud_range(struct mmu_gather *tlb, 525 struct vm_area_struct *vma, p4d_t *p4d, unsigned long addr, 526 unsigned long end, pgprot_t newprot, unsigned long cp_flags) 527 { 528 struct mmu_notifier_range range; 529 pud_t *pudp, pud; 530 unsigned long next; 531 long pages = 0, ret; 532 533 range.start = 0; 534 535 pudp = pud_offset(p4d, addr); 536 do { 537 again: 538 next = pud_addr_end(addr, end); 539 ret = change_prepare(vma, pudp, pmd, addr, cp_flags); 540 if (ret) { 541 pages = ret; 542 break; 543 } 544 545 pud = pudp_get(pudp); 546 if (pud_none(pud)) 547 continue; 548 549 if (!range.start) { 550 mmu_notifier_range_init(&range, 551 MMU_NOTIFY_PROTECTION_VMA, 0, 552 vma->vm_mm, addr, end); 553 mmu_notifier_invalidate_range_start(&range); 554 } 555 556 if (pud_leaf(pud)) { 557 if ((next - addr != PUD_SIZE) || 558 pgtable_split_needed(vma, cp_flags)) { 559 __split_huge_pud(vma, pudp, addr); 560 goto again; 561 } else { 562 ret = change_huge_pud(tlb, vma, pudp, 563 addr, newprot, cp_flags); 564 if (ret == 0) 565 goto again; 566 /* huge pud was handled */ 567 if (ret == HPAGE_PUD_NR) 568 pages += HPAGE_PUD_NR; 569 continue; 570 } 571 } 572 573 pages += change_pmd_range(tlb, vma, pudp, addr, next, newprot, 574 cp_flags); 575 } while (pudp++, addr = next, addr != end); 576 577 if (range.start) 578 mmu_notifier_invalidate_range_end(&range); 579 580 return pages; 581 } 582 583 static inline long change_p4d_range(struct mmu_gather *tlb, 584 struct vm_area_struct *vma, pgd_t *pgd, unsigned long addr, 585 unsigned long end, pgprot_t newprot, unsigned long cp_flags) 586 { 587 p4d_t *p4d; 588 unsigned long next; 589 long pages = 0, ret; 590 591 p4d = p4d_offset(pgd, addr); 592 do { 593 next = p4d_addr_end(addr, end); 594 ret = change_prepare(vma, p4d, pud, addr, cp_flags); 595 if (ret) 596 return ret; 597 if (p4d_none_or_clear_bad(p4d)) 598 continue; 599 pages += change_pud_range(tlb, vma, p4d, addr, next, newprot, 600 cp_flags); 601 } while (p4d++, addr = next, addr != end); 602 603 return pages; 604 } 605 606 static long change_protection_range(struct mmu_gather *tlb, 607 struct vm_area_struct *vma, unsigned long addr, 608 unsigned long end, pgprot_t newprot, unsigned long cp_flags) 609 { 610 struct mm_struct *mm = vma->vm_mm; 611 pgd_t *pgd; 612 unsigned long next; 613 long pages = 0, ret; 614 615 BUG_ON(addr >= end); 616 pgd = pgd_offset(mm, addr); 617 tlb_start_vma(tlb, vma); 618 do { 619 next = pgd_addr_end(addr, end); 620 ret = change_prepare(vma, pgd, p4d, addr, cp_flags); 621 if (ret) { 622 pages = ret; 623 break; 624 } 625 if (pgd_none_or_clear_bad(pgd)) 626 continue; 627 pages += change_p4d_range(tlb, vma, pgd, addr, next, newprot, 628 cp_flags); 629 } while (pgd++, addr = next, addr != end); 630 631 tlb_end_vma(tlb, vma); 632 633 return pages; 634 } 635 636 long change_protection(struct mmu_gather *tlb, 637 struct vm_area_struct *vma, unsigned long start, 638 unsigned long end, unsigned long cp_flags) 639 { 640 pgprot_t newprot = vma->vm_page_prot; 641 long pages; 642 643 BUG_ON((cp_flags & MM_CP_UFFD_WP_ALL) == MM_CP_UFFD_WP_ALL); 644 645 #ifdef CONFIG_NUMA_BALANCING 646 /* 647 * Ordinary protection updates (mprotect, uffd-wp, softdirty tracking) 648 * are expected to reflect their requirements via VMA flags such that 649 * vma_set_page_prot() will adjust vma->vm_page_prot accordingly. 650 */ 651 if (cp_flags & MM_CP_PROT_NUMA) 652 newprot = PAGE_NONE; 653 #else 654 WARN_ON_ONCE(cp_flags & MM_CP_PROT_NUMA); 655 #endif 656 657 if (is_vm_hugetlb_page(vma)) 658 pages = hugetlb_change_protection(vma, start, end, newprot, 659 cp_flags); 660 else 661 pages = change_protection_range(tlb, vma, start, end, newprot, 662 cp_flags); 663 664 return pages; 665 } 666 667 static int prot_none_pte_entry(pte_t *pte, unsigned long addr, 668 unsigned long next, struct mm_walk *walk) 669 { 670 return pfn_modify_allowed(pte_pfn(ptep_get(pte)), 671 *(pgprot_t *)(walk->private)) ? 672 0 : -EACCES; 673 } 674 675 static int prot_none_hugetlb_entry(pte_t *pte, unsigned long hmask, 676 unsigned long addr, unsigned long next, 677 struct mm_walk *walk) 678 { 679 return pfn_modify_allowed(pte_pfn(ptep_get(pte)), 680 *(pgprot_t *)(walk->private)) ? 681 0 : -EACCES; 682 } 683 684 static int prot_none_test(unsigned long addr, unsigned long next, 685 struct mm_walk *walk) 686 { 687 return 0; 688 } 689 690 static const struct mm_walk_ops prot_none_walk_ops = { 691 .pte_entry = prot_none_pte_entry, 692 .hugetlb_entry = prot_none_hugetlb_entry, 693 .test_walk = prot_none_test, 694 .walk_lock = PGWALK_WRLOCK, 695 }; 696 697 int 698 mprotect_fixup(struct vma_iterator *vmi, struct mmu_gather *tlb, 699 struct vm_area_struct *vma, struct vm_area_struct **pprev, 700 unsigned long start, unsigned long end, vm_flags_t newflags) 701 { 702 struct mm_struct *mm = vma->vm_mm; 703 vm_flags_t oldflags = READ_ONCE(vma->vm_flags); 704 long nrpages = (end - start) >> PAGE_SHIFT; 705 unsigned int mm_cp_flags = 0; 706 unsigned long charged = 0; 707 int error; 708 709 if (vma_is_sealed(vma)) 710 return -EPERM; 711 712 if (newflags == oldflags) { 713 *pprev = vma; 714 return 0; 715 } 716 717 /* 718 * Do PROT_NONE PFN permission checks here when we can still 719 * bail out without undoing a lot of state. This is a rather 720 * uncommon case, so doesn't need to be very optimized. 721 */ 722 if (arch_has_pfn_modify_check() && 723 (oldflags & (VM_PFNMAP|VM_MIXEDMAP)) && 724 (newflags & VM_ACCESS_FLAGS) == 0) { 725 pgprot_t new_pgprot = vm_get_page_prot(newflags); 726 727 error = walk_page_range(current->mm, start, end, 728 &prot_none_walk_ops, &new_pgprot); 729 if (error) 730 return error; 731 } 732 733 /* 734 * If we make a private mapping writable we increase our commit; 735 * but (without finer accounting) cannot reduce our commit if we 736 * make it unwritable again except in the anonymous case where no 737 * anon_vma has yet to be assigned. 738 * 739 * hugetlb mapping were accounted for even if read-only so there is 740 * no need to account for them here. 741 */ 742 if (newflags & VM_WRITE) { 743 /* Check space limits when area turns into data. */ 744 if (!may_expand_vm(mm, newflags, nrpages) && 745 may_expand_vm(mm, oldflags, nrpages)) 746 return -ENOMEM; 747 if (!(oldflags & (VM_ACCOUNT|VM_WRITE|VM_HUGETLB| 748 VM_SHARED|VM_NORESERVE))) { 749 charged = nrpages; 750 if (security_vm_enough_memory_mm(mm, charged)) 751 return -ENOMEM; 752 newflags |= VM_ACCOUNT; 753 } 754 } else if ((oldflags & VM_ACCOUNT) && vma_is_anonymous(vma) && 755 !vma->anon_vma) { 756 newflags &= ~VM_ACCOUNT; 757 } 758 759 vma = vma_modify_flags(vmi, *pprev, vma, start, end, &newflags); 760 if (IS_ERR(vma)) { 761 error = PTR_ERR(vma); 762 goto fail; 763 } 764 765 *pprev = vma; 766 767 /* 768 * vm_flags and vm_page_prot are protected by the mmap_lock 769 * held in write mode. 770 */ 771 vma_start_write(vma); 772 vm_flags_reset_once(vma, newflags); 773 if (vma_wants_manual_pte_write_upgrade(vma)) 774 mm_cp_flags |= MM_CP_TRY_CHANGE_WRITABLE; 775 vma_set_page_prot(vma); 776 777 change_protection(tlb, vma, start, end, mm_cp_flags); 778 779 if ((oldflags & VM_ACCOUNT) && !(newflags & VM_ACCOUNT)) 780 vm_unacct_memory(nrpages); 781 782 /* 783 * Private VM_LOCKED VMA becoming writable: trigger COW to avoid major 784 * fault on access. 785 */ 786 if ((oldflags & (VM_WRITE | VM_SHARED | VM_LOCKED)) == VM_LOCKED && 787 (newflags & VM_WRITE)) { 788 populate_vma_page_range(vma, start, end, NULL); 789 } 790 791 vm_stat_account(mm, oldflags, -nrpages); 792 vm_stat_account(mm, newflags, nrpages); 793 perf_event_mmap(vma); 794 return 0; 795 796 fail: 797 vm_unacct_memory(charged); 798 return error; 799 } 800 801 /* 802 * pkey==-1 when doing a legacy mprotect() 803 */ 804 static int do_mprotect_pkey(unsigned long start, size_t len, 805 unsigned long prot, int pkey) 806 { 807 unsigned long nstart, end, tmp, reqprot; 808 struct vm_area_struct *vma, *prev; 809 int error; 810 const int grows = prot & (PROT_GROWSDOWN|PROT_GROWSUP); 811 const bool rier = (current->personality & READ_IMPLIES_EXEC) && 812 (prot & PROT_READ); 813 struct mmu_gather tlb; 814 struct vma_iterator vmi; 815 816 start = untagged_addr(start); 817 818 prot &= ~(PROT_GROWSDOWN|PROT_GROWSUP); 819 if (grows == (PROT_GROWSDOWN|PROT_GROWSUP)) /* can't be both */ 820 return -EINVAL; 821 822 if (start & ~PAGE_MASK) 823 return -EINVAL; 824 if (!len) 825 return 0; 826 len = PAGE_ALIGN(len); 827 end = start + len; 828 if (end <= start) 829 return -ENOMEM; 830 if (!arch_validate_prot(prot, start)) 831 return -EINVAL; 832 833 reqprot = prot; 834 835 if (mmap_write_lock_killable(current->mm)) 836 return -EINTR; 837 838 /* 839 * If userspace did not allocate the pkey, do not let 840 * them use it here. 841 */ 842 error = -EINVAL; 843 if ((pkey != -1) && !mm_pkey_is_allocated(current->mm, pkey)) 844 goto out; 845 846 vma_iter_init(&vmi, current->mm, start); 847 vma = vma_find(&vmi, end); 848 error = -ENOMEM; 849 if (!vma) 850 goto out; 851 852 if (unlikely(grows & PROT_GROWSDOWN)) { 853 if (vma->vm_start >= end) 854 goto out; 855 start = vma->vm_start; 856 error = -EINVAL; 857 if (!(vma->vm_flags & VM_GROWSDOWN)) 858 goto out; 859 } else { 860 if (vma->vm_start > start) 861 goto out; 862 if (unlikely(grows & PROT_GROWSUP)) { 863 end = vma->vm_end; 864 error = -EINVAL; 865 if (!(vma->vm_flags & VM_GROWSUP)) 866 goto out; 867 } 868 } 869 870 prev = vma_prev(&vmi); 871 if (start > vma->vm_start) 872 prev = vma; 873 874 tlb_gather_mmu(&tlb, current->mm); 875 nstart = start; 876 tmp = vma->vm_start; 877 for_each_vma_range(vmi, vma, end) { 878 vm_flags_t mask_off_old_flags; 879 vm_flags_t newflags; 880 int new_vma_pkey; 881 882 if (vma->vm_start != tmp) { 883 error = -ENOMEM; 884 break; 885 } 886 887 /* Does the application expect PROT_READ to imply PROT_EXEC */ 888 if (rier && (vma->vm_flags & VM_MAYEXEC)) 889 prot |= PROT_EXEC; 890 891 /* 892 * Each mprotect() call explicitly passes r/w/x permissions. 893 * If a permission is not passed to mprotect(), it must be 894 * cleared from the VMA. 895 */ 896 mask_off_old_flags = VM_ACCESS_FLAGS | VM_FLAGS_CLEAR; 897 898 new_vma_pkey = arch_override_mprotect_pkey(vma, prot, pkey); 899 newflags = calc_vm_prot_bits(prot, new_vma_pkey); 900 newflags |= (vma->vm_flags & ~mask_off_old_flags); 901 902 /* newflags >> 4 shift VM_MAY% in place of VM_% */ 903 if ((newflags & ~(newflags >> 4)) & VM_ACCESS_FLAGS) { 904 error = -EACCES; 905 break; 906 } 907 908 if (map_deny_write_exec(vma->vm_flags, newflags)) { 909 error = -EACCES; 910 break; 911 } 912 913 /* Allow architectures to sanity-check the new flags */ 914 if (!arch_validate_flags(newflags)) { 915 error = -EINVAL; 916 break; 917 } 918 919 error = security_file_mprotect(vma, reqprot, prot); 920 if (error) 921 break; 922 923 tmp = vma->vm_end; 924 if (tmp > end) 925 tmp = end; 926 927 if (vma->vm_ops && vma->vm_ops->mprotect) { 928 error = vma->vm_ops->mprotect(vma, nstart, tmp, newflags); 929 if (error) 930 break; 931 } 932 933 error = mprotect_fixup(&vmi, &tlb, vma, &prev, nstart, tmp, newflags); 934 if (error) 935 break; 936 937 tmp = vma_iter_end(&vmi); 938 nstart = tmp; 939 prot = reqprot; 940 } 941 tlb_finish_mmu(&tlb); 942 943 if (!error && tmp < end) 944 error = -ENOMEM; 945 946 out: 947 mmap_write_unlock(current->mm); 948 return error; 949 } 950 951 SYSCALL_DEFINE3(mprotect, unsigned long, start, size_t, len, 952 unsigned long, prot) 953 { 954 return do_mprotect_pkey(start, len, prot, -1); 955 } 956 957 #ifdef CONFIG_ARCH_HAS_PKEYS 958 959 SYSCALL_DEFINE4(pkey_mprotect, unsigned long, start, size_t, len, 960 unsigned long, prot, int, pkey) 961 { 962 return do_mprotect_pkey(start, len, prot, pkey); 963 } 964 965 SYSCALL_DEFINE2(pkey_alloc, unsigned long, flags, unsigned long, init_val) 966 { 967 int pkey; 968 int ret; 969 970 /* No flags supported yet. */ 971 if (flags) 972 return -EINVAL; 973 /* check for unsupported init values */ 974 if (init_val & ~PKEY_ACCESS_MASK) 975 return -EINVAL; 976 977 mmap_write_lock(current->mm); 978 pkey = mm_pkey_alloc(current->mm); 979 980 ret = -ENOSPC; 981 if (pkey == -1) 982 goto out; 983 984 ret = arch_set_user_pkey_access(current, pkey, init_val); 985 if (ret) { 986 mm_pkey_free(current->mm, pkey); 987 goto out; 988 } 989 ret = pkey; 990 out: 991 mmap_write_unlock(current->mm); 992 return ret; 993 } 994 995 SYSCALL_DEFINE1(pkey_free, int, pkey) 996 { 997 int ret; 998 999 mmap_write_lock(current->mm); 1000 ret = mm_pkey_free(current->mm, pkey); 1001 mmap_write_unlock(current->mm); 1002 1003 /* 1004 * We could provide warnings or errors if any VMA still 1005 * has the pkey set here. 1006 */ 1007 return ret; 1008 } 1009 1010 #endif /* CONFIG_ARCH_HAS_PKEYS */ 1011