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

source code of linux/mm/mprotect.c