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

source code of linux/mm/mprotect.c