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
can_change_pte_writable(struct vm_area_struct * vma,unsigned long addr,pte_t pte)43 bool 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
change_pte_range(struct mmu_gather * tlb,struct vm_area_struct * vma,pmd_t * pmd,unsigned long addr,unsigned long end,pgprot_t newprot,unsigned long cp_flags)86 static 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(vma->vm_mm, pmd, addr, &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(&vma->vm_mm->mm_users) == 1)
106 target_node = numa_node_id();
107
108 flush_tlb_batched_pending(vma->vm_mm);
109 arch_enter_lazy_mmu_mode();
110 do {
111 oldpte = ptep_get(pte);
112 if (pte_present(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(oldpte))
126 continue;
127
128 folio = vm_normal_folio(vma, addr, 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(vma->vm_flags) &&
135 (folio_maybe_dma_pinned(folio) ||
136 folio_likely_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(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 jiffies_to_msecs(jiffies));
167 }
168
169 oldpte = ptep_modify_prot_start(vma, addr, pte);
170 ptent = pte_modify(oldpte, newprot);
171
172 if (uffd_wp)
173 ptent = pte_mkuffd_wp(ptent);
174 else if (uffd_wp_resolve)
175 ptent = pte_clear_uffd_wp(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(ptent) &&
192 can_change_pte_writable(vma, addr, ptent))
193 ptent = pte_mkwrite(ptent, vma);
194
195 ptep_modify_prot_commit(vma, addr, pte, oldpte, ptent);
196 if (pte_needs_flush(oldpte, ptent))
197 tlb_flush_pte_range(tlb, addr, PAGE_SIZE);
198 pages++;
199 } else if (is_swap_pte(oldpte)) {
200 swp_entry_t entry = pte_to_swp_entry(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 swp_offset(entry));
213 else
214 entry = make_readable_migration_entry(swp_offset(entry));
215 newpte = swp_entry_to_pte(entry);
216 if (pte_swp_soft_dirty(oldpte))
217 newpte = pte_swp_mksoft_dirty(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 swp_offset(entry));
225 newpte = swp_entry_to_pte(entry);
226 if (pte_swp_uffd_wp(oldpte))
227 newpte = pte_swp_mkuffd_wp(newpte);
228 } else if (is_writable_device_exclusive_entry(entry)) {
229 entry = make_readable_device_exclusive_entry(
230 swp_offset(entry));
231 newpte = swp_entry_to_pte(entry);
232 if (pte_swp_soft_dirty(oldpte))
233 newpte = pte_swp_mksoft_dirty(newpte);
234 if (pte_swp_uffd_wp(oldpte))
235 newpte = pte_swp_mkuffd_wp(newpte);
236 } else if (is_pte_marker_entry(entry)) {
237 /*
238 * Ignore error swap entries unconditionally,
239 * because any access should sigbus anyway.
240 */
241 if (is_poisoned_swp_entry(entry))
242 continue;
243 /*
244 * If this is uffd-wp pte marker and we'd like
245 * to unprotect it, drop it; the next page
246 * fault will trigger without uffd trapping.
247 */
248 if (uffd_wp_resolve) {
249 pte_clear(vma->vm_mm, addr, pte);
250 pages++;
251 }
252 continue;
253 } else {
254 newpte = oldpte;
255 }
256
257 if (uffd_wp)
258 newpte = pte_swp_mkuffd_wp(newpte);
259 else if (uffd_wp_resolve)
260 newpte = pte_swp_clear_uffd_wp(newpte);
261
262 if (!pte_same(oldpte, newpte)) {
263 set_pte_at(vma->vm_mm, addr, pte, newpte);
264 pages++;
265 }
266 } else {
267 /* It must be an none page, or what else?.. */
268 WARN_ON_ONCE(!pte_none(oldpte));
269
270 /*
271 * Nobody plays with any none ptes besides
272 * userfaultfd when applying the protections.
273 */
274 if (likely(!uffd_wp))
275 continue;
276
277 if (userfaultfd_wp_use_markers(vma)) {
278 /*
279 * For file-backed mem, we need to be able to
280 * wr-protect a none pte, because even if the
281 * pte is none, the page/swap cache could
282 * exist. Doing that by install a marker.
283 */
284 set_pte_at(vma->vm_mm, addr, pte,
285 make_pte_marker(PTE_MARKER_UFFD_WP));
286 pages++;
287 }
288 }
289 } while (pte++, addr += PAGE_SIZE, addr != end);
290 arch_leave_lazy_mmu_mode();
291 pte_unmap_unlock(pte - 1, ptl);
292
293 return pages;
294 }
295
296 /*
297 * Return true if we want to split THPs into PTE mappings in change
298 * protection procedure, false otherwise.
299 */
300 static inline bool
pgtable_split_needed(struct vm_area_struct * vma,unsigned long cp_flags)301 pgtable_split_needed(struct vm_area_struct *vma, unsigned long cp_flags)
302 {
303 /*
304 * pte markers only resides in pte level, if we need pte markers,
305 * we need to split. For example, we cannot wr-protect a file thp
306 * (e.g. 2M shmem) because file thp is handled differently when
307 * split by erasing the pmd so far.
308 */
309 return (cp_flags & MM_CP_UFFD_WP) && !vma_is_anonymous(vma);
310 }
311
312 /*
313 * Return true if we want to populate pgtables in change protection
314 * procedure, false otherwise
315 */
316 static inline bool
pgtable_populate_needed(struct vm_area_struct * vma,unsigned long cp_flags)317 pgtable_populate_needed(struct vm_area_struct *vma, unsigned long cp_flags)
318 {
319 /* If not within ioctl(UFFDIO_WRITEPROTECT), then don't bother */
320 if (!(cp_flags & MM_CP_UFFD_WP))
321 return false;
322
323 /* Populate if the userfaultfd mode requires pte markers */
324 return userfaultfd_wp_use_markers(vma);
325 }
326
327 /*
328 * Populate the pgtable underneath for whatever reason if requested.
329 * When {pte|pmd|...}_alloc() failed we treat it the same way as pgtable
330 * allocation failures during page faults by kicking OOM and returning
331 * error.
332 */
333 #define change_pmd_prepare(vma, pmd, cp_flags) \
334 ({ \
335 long err = 0; \
336 if (unlikely(pgtable_populate_needed(vma, cp_flags))) { \
337 if (pte_alloc(vma->vm_mm, pmd)) \
338 err = -ENOMEM; \
339 } \
340 err; \
341 })
342
343 /*
344 * This is the general pud/p4d/pgd version of change_pmd_prepare(). We need to
345 * have separate change_pmd_prepare() because pte_alloc() returns 0 on success,
346 * while {pmd|pud|p4d}_alloc() returns the valid pointer on success.
347 */
348 #define change_prepare(vma, high, low, addr, cp_flags) \
349 ({ \
350 long err = 0; \
351 if (unlikely(pgtable_populate_needed(vma, cp_flags))) { \
352 low##_t *p = low##_alloc(vma->vm_mm, high, addr); \
353 if (p == NULL) \
354 err = -ENOMEM; \
355 } \
356 err; \
357 })
358
change_pmd_range(struct mmu_gather * tlb,struct vm_area_struct * vma,pud_t * pud,unsigned long addr,unsigned long end,pgprot_t newprot,unsigned long cp_flags)359 static inline long change_pmd_range(struct mmu_gather *tlb,
360 struct vm_area_struct *vma, pud_t *pud, unsigned long addr,
361 unsigned long end, pgprot_t newprot, unsigned long cp_flags)
362 {
363 pmd_t *pmd;
364 unsigned long next;
365 long pages = 0;
366 unsigned long nr_huge_updates = 0;
367
368 pmd = pmd_offset(pud, addr);
369 do {
370 long ret;
371 pmd_t _pmd;
372 again:
373 next = pmd_addr_end(addr, end);
374
375 ret = change_pmd_prepare(vma, pmd, cp_flags);
376 if (ret) {
377 pages = ret;
378 break;
379 }
380
381 if (pmd_none(*pmd))
382 goto next;
383
384 _pmd = pmdp_get_lockless(pmd);
385 if (is_swap_pmd(_pmd) || pmd_trans_huge(_pmd) || pmd_devmap(_pmd)) {
386 if ((next - addr != HPAGE_PMD_SIZE) ||
387 pgtable_split_needed(vma, cp_flags)) {
388 __split_huge_pmd(vma, pmd, addr, false, NULL);
389 /*
390 * For file-backed, the pmd could have been
391 * cleared; make sure pmd populated if
392 * necessary, then fall-through to pte level.
393 */
394 ret = change_pmd_prepare(vma, pmd, cp_flags);
395 if (ret) {
396 pages = ret;
397 break;
398 }
399 } else {
400 ret = change_huge_pmd(tlb, vma, pmd,
401 addr, newprot, cp_flags);
402 if (ret) {
403 if (ret == HPAGE_PMD_NR) {
404 pages += HPAGE_PMD_NR;
405 nr_huge_updates++;
406 }
407
408 /* huge pmd was handled */
409 goto next;
410 }
411 }
412 /* fall through, the trans huge pmd just split */
413 }
414
415 ret = change_pte_range(tlb, vma, pmd, addr, next, newprot,
416 cp_flags);
417 if (ret < 0)
418 goto again;
419 pages += ret;
420 next:
421 cond_resched();
422 } while (pmd++, addr = next, addr != end);
423
424 if (nr_huge_updates)
425 count_vm_numa_events(NUMA_HUGE_PTE_UPDATES, nr_huge_updates);
426 return pages;
427 }
428
change_pud_range(struct mmu_gather * tlb,struct vm_area_struct * vma,p4d_t * p4d,unsigned long addr,unsigned long end,pgprot_t newprot,unsigned long cp_flags)429 static inline long change_pud_range(struct mmu_gather *tlb,
430 struct vm_area_struct *vma, p4d_t *p4d, unsigned long addr,
431 unsigned long end, pgprot_t newprot, unsigned long cp_flags)
432 {
433 struct mmu_notifier_range range;
434 pud_t *pudp, pud;
435 unsigned long next;
436 long pages = 0, ret;
437
438 range.start = 0;
439
440 pudp = pud_offset(p4d, addr);
441 do {
442 again:
443 next = pud_addr_end(addr, end);
444 ret = change_prepare(vma, pudp, pmd, addr, cp_flags);
445 if (ret) {
446 pages = ret;
447 break;
448 }
449
450 pud = READ_ONCE(*pudp);
451 if (pud_none(pud))
452 continue;
453
454 if (!range.start) {
455 mmu_notifier_range_init(&range,
456 MMU_NOTIFY_PROTECTION_VMA, 0,
457 vma->vm_mm, addr, end);
458 mmu_notifier_invalidate_range_start(&range);
459 }
460
461 if (pud_leaf(pud)) {
462 if ((next - addr != PUD_SIZE) ||
463 pgtable_split_needed(vma, cp_flags)) {
464 __split_huge_pud(vma, pudp, addr);
465 goto again;
466 } else {
467 ret = change_huge_pud(tlb, vma, pudp,
468 addr, newprot, cp_flags);
469 if (ret == 0)
470 goto again;
471 /* huge pud was handled */
472 if (ret == HPAGE_PUD_NR)
473 pages += HPAGE_PUD_NR;
474 continue;
475 }
476 }
477
478 pages += change_pmd_range(tlb, vma, pudp, addr, next, newprot,
479 cp_flags);
480 } while (pudp++, addr = next, addr != end);
481
482 if (range.start)
483 mmu_notifier_invalidate_range_end(&range);
484
485 return pages;
486 }
487
change_p4d_range(struct mmu_gather * tlb,struct vm_area_struct * vma,pgd_t * pgd,unsigned long addr,unsigned long end,pgprot_t newprot,unsigned long cp_flags)488 static inline long change_p4d_range(struct mmu_gather *tlb,
489 struct vm_area_struct *vma, pgd_t *pgd, unsigned long addr,
490 unsigned long end, pgprot_t newprot, unsigned long cp_flags)
491 {
492 p4d_t *p4d;
493 unsigned long next;
494 long pages = 0, ret;
495
496 p4d = p4d_offset(pgd, addr);
497 do {
498 next = p4d_addr_end(addr, end);
499 ret = change_prepare(vma, p4d, pud, addr, cp_flags);
500 if (ret)
501 return ret;
502 if (p4d_none_or_clear_bad(p4d))
503 continue;
504 pages += change_pud_range(tlb, vma, p4d, addr, next, newprot,
505 cp_flags);
506 } while (p4d++, addr = next, addr != end);
507
508 return pages;
509 }
510
change_protection_range(struct mmu_gather * tlb,struct vm_area_struct * vma,unsigned long addr,unsigned long end,pgprot_t newprot,unsigned long cp_flags)511 static long change_protection_range(struct mmu_gather *tlb,
512 struct vm_area_struct *vma, unsigned long addr,
513 unsigned long end, pgprot_t newprot, unsigned long cp_flags)
514 {
515 struct mm_struct *mm = vma->vm_mm;
516 pgd_t *pgd;
517 unsigned long next;
518 long pages = 0, ret;
519
520 BUG_ON(addr >= end);
521 pgd = pgd_offset(mm, addr);
522 tlb_start_vma(tlb, vma);
523 do {
524 next = pgd_addr_end(addr, end);
525 ret = change_prepare(vma, pgd, p4d, addr, cp_flags);
526 if (ret) {
527 pages = ret;
528 break;
529 }
530 if (pgd_none_or_clear_bad(pgd))
531 continue;
532 pages += change_p4d_range(tlb, vma, pgd, addr, next, newprot,
533 cp_flags);
534 } while (pgd++, addr = next, addr != end);
535
536 tlb_end_vma(tlb, vma);
537
538 return pages;
539 }
540
change_protection(struct mmu_gather * tlb,struct vm_area_struct * vma,unsigned long start,unsigned long end,unsigned long cp_flags)541 long change_protection(struct mmu_gather *tlb,
542 struct vm_area_struct *vma, unsigned long start,
543 unsigned long end, unsigned long cp_flags)
544 {
545 pgprot_t newprot = vma->vm_page_prot;
546 long pages;
547
548 BUG_ON((cp_flags & MM_CP_UFFD_WP_ALL) == MM_CP_UFFD_WP_ALL);
549
550 #ifdef CONFIG_NUMA_BALANCING
551 /*
552 * Ordinary protection updates (mprotect, uffd-wp, softdirty tracking)
553 * are expected to reflect their requirements via VMA flags such that
554 * vma_set_page_prot() will adjust vma->vm_page_prot accordingly.
555 */
556 if (cp_flags & MM_CP_PROT_NUMA)
557 newprot = PAGE_NONE;
558 #else
559 WARN_ON_ONCE(cp_flags & MM_CP_PROT_NUMA);
560 #endif
561
562 if (is_vm_hugetlb_page(vma))
563 pages = hugetlb_change_protection(vma, start, end, newprot,
564 cp_flags);
565 else
566 pages = change_protection_range(tlb, vma, start, end, newprot,
567 cp_flags);
568
569 return pages;
570 }
571
prot_none_pte_entry(pte_t * pte,unsigned long addr,unsigned long next,struct mm_walk * walk)572 static int prot_none_pte_entry(pte_t *pte, unsigned long addr,
573 unsigned long next, struct mm_walk *walk)
574 {
575 return pfn_modify_allowed(pte_pfn(ptep_get(pte)),
576 *(pgprot_t *)(walk->private)) ?
577 0 : -EACCES;
578 }
579
prot_none_hugetlb_entry(pte_t * pte,unsigned long hmask,unsigned long addr,unsigned long next,struct mm_walk * walk)580 static int prot_none_hugetlb_entry(pte_t *pte, unsigned long hmask,
581 unsigned long addr, unsigned long next,
582 struct mm_walk *walk)
583 {
584 return pfn_modify_allowed(pte_pfn(ptep_get(pte)),
585 *(pgprot_t *)(walk->private)) ?
586 0 : -EACCES;
587 }
588
prot_none_test(unsigned long addr,unsigned long next,struct mm_walk * walk)589 static int prot_none_test(unsigned long addr, unsigned long next,
590 struct mm_walk *walk)
591 {
592 return 0;
593 }
594
595 static const struct mm_walk_ops prot_none_walk_ops = {
596 .pte_entry = prot_none_pte_entry,
597 .hugetlb_entry = prot_none_hugetlb_entry,
598 .test_walk = prot_none_test,
599 .walk_lock = PGWALK_WRLOCK,
600 };
601
602 int
mprotect_fixup(struct vma_iterator * vmi,struct mmu_gather * tlb,struct vm_area_struct * vma,struct vm_area_struct ** pprev,unsigned long start,unsigned long end,unsigned long newflags)603 mprotect_fixup(struct vma_iterator *vmi, struct mmu_gather *tlb,
604 struct vm_area_struct *vma, struct vm_area_struct **pprev,
605 unsigned long start, unsigned long end, unsigned long newflags)
606 {
607 struct mm_struct *mm = vma->vm_mm;
608 unsigned long oldflags = vma->vm_flags;
609 long nrpages = (end - start) >> PAGE_SHIFT;
610 unsigned int mm_cp_flags = 0;
611 unsigned long charged = 0;
612 int error;
613
614 if (!can_modify_vma(vma))
615 return -EPERM;
616
617 if (newflags == oldflags) {
618 *pprev = vma;
619 return 0;
620 }
621
622 /*
623 * Do PROT_NONE PFN permission checks here when we can still
624 * bail out without undoing a lot of state. This is a rather
625 * uncommon case, so doesn't need to be very optimized.
626 */
627 if (arch_has_pfn_modify_check() &&
628 (vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
629 (newflags & VM_ACCESS_FLAGS) == 0) {
630 pgprot_t new_pgprot = vm_get_page_prot(newflags);
631
632 error = walk_page_range(current->mm, start, end,
633 &prot_none_walk_ops, &new_pgprot);
634 if (error)
635 return error;
636 }
637
638 /*
639 * If we make a private mapping writable we increase our commit;
640 * but (without finer accounting) cannot reduce our commit if we
641 * make it unwritable again except in the anonymous case where no
642 * anon_vma has yet to be assigned.
643 *
644 * hugetlb mapping were accounted for even if read-only so there is
645 * no need to account for them here.
646 */
647 if (newflags & VM_WRITE) {
648 /* Check space limits when area turns into data. */
649 if (!may_expand_vm(mm, newflags, nrpages) &&
650 may_expand_vm(mm, oldflags, nrpages))
651 return -ENOMEM;
652 if (!(oldflags & (VM_ACCOUNT|VM_WRITE|VM_HUGETLB|
653 VM_SHARED|VM_NORESERVE))) {
654 charged = nrpages;
655 if (security_vm_enough_memory_mm(mm, charged))
656 return -ENOMEM;
657 newflags |= VM_ACCOUNT;
658 }
659 } else if ((oldflags & VM_ACCOUNT) && vma_is_anonymous(vma) &&
660 !vma->anon_vma) {
661 newflags &= ~VM_ACCOUNT;
662 }
663
664 vma = vma_modify_flags(vmi, *pprev, vma, start, end, newflags);
665 if (IS_ERR(vma)) {
666 error = PTR_ERR(vma);
667 goto fail;
668 }
669
670 *pprev = vma;
671
672 /*
673 * vm_flags and vm_page_prot are protected by the mmap_lock
674 * held in write mode.
675 */
676 vma_start_write(vma);
677 vm_flags_reset(vma, newflags);
678 if (vma_wants_manual_pte_write_upgrade(vma))
679 mm_cp_flags |= MM_CP_TRY_CHANGE_WRITABLE;
680 vma_set_page_prot(vma);
681
682 change_protection(tlb, vma, start, end, mm_cp_flags);
683
684 if ((oldflags & VM_ACCOUNT) && !(newflags & VM_ACCOUNT))
685 vm_unacct_memory(nrpages);
686
687 /*
688 * Private VM_LOCKED VMA becoming writable: trigger COW to avoid major
689 * fault on access.
690 */
691 if ((oldflags & (VM_WRITE | VM_SHARED | VM_LOCKED)) == VM_LOCKED &&
692 (newflags & VM_WRITE)) {
693 populate_vma_page_range(vma, start, end, NULL);
694 }
695
696 vm_stat_account(mm, oldflags, -nrpages);
697 vm_stat_account(mm, newflags, nrpages);
698 perf_event_mmap(vma);
699 return 0;
700
701 fail:
702 vm_unacct_memory(charged);
703 return error;
704 }
705
706 /*
707 * pkey==-1 when doing a legacy mprotect()
708 */
do_mprotect_pkey(unsigned long start,size_t len,unsigned long prot,int pkey)709 static int do_mprotect_pkey(unsigned long start, size_t len,
710 unsigned long prot, int pkey)
711 {
712 unsigned long nstart, end, tmp, reqprot;
713 struct vm_area_struct *vma, *prev;
714 int error;
715 const int grows = prot & (PROT_GROWSDOWN|PROT_GROWSUP);
716 const bool rier = (current->personality & READ_IMPLIES_EXEC) &&
717 (prot & PROT_READ);
718 struct mmu_gather tlb;
719 struct vma_iterator vmi;
720
721 start = untagged_addr(start);
722
723 prot &= ~(PROT_GROWSDOWN|PROT_GROWSUP);
724 if (grows == (PROT_GROWSDOWN|PROT_GROWSUP)) /* can't be both */
725 return -EINVAL;
726
727 if (start & ~PAGE_MASK)
728 return -EINVAL;
729 if (!len)
730 return 0;
731 len = PAGE_ALIGN(len);
732 end = start + len;
733 if (end <= start)
734 return -ENOMEM;
735 if (!arch_validate_prot(prot, start))
736 return -EINVAL;
737
738 reqprot = prot;
739
740 if (mmap_write_lock_killable(current->mm))
741 return -EINTR;
742
743 /*
744 * If userspace did not allocate the pkey, do not let
745 * them use it here.
746 */
747 error = -EINVAL;
748 if ((pkey != -1) && !mm_pkey_is_allocated(current->mm, pkey))
749 goto out;
750
751 vma_iter_init(&vmi, current->mm, start);
752 vma = vma_find(&vmi, end);
753 error = -ENOMEM;
754 if (!vma)
755 goto out;
756
757 if (unlikely(grows & PROT_GROWSDOWN)) {
758 if (vma->vm_start >= end)
759 goto out;
760 start = vma->vm_start;
761 error = -EINVAL;
762 if (!(vma->vm_flags & VM_GROWSDOWN))
763 goto out;
764 } else {
765 if (vma->vm_start > start)
766 goto out;
767 if (unlikely(grows & PROT_GROWSUP)) {
768 end = vma->vm_end;
769 error = -EINVAL;
770 if (!(vma->vm_flags & VM_GROWSUP))
771 goto out;
772 }
773 }
774
775 prev = vma_prev(&vmi);
776 if (start > vma->vm_start)
777 prev = vma;
778
779 tlb_gather_mmu(&tlb, current->mm);
780 nstart = start;
781 tmp = vma->vm_start;
782 for_each_vma_range(vmi, vma, end) {
783 unsigned long mask_off_old_flags;
784 unsigned long newflags;
785 int new_vma_pkey;
786
787 if (vma->vm_start != tmp) {
788 error = -ENOMEM;
789 break;
790 }
791
792 /* Does the application expect PROT_READ to imply PROT_EXEC */
793 if (rier && (vma->vm_flags & VM_MAYEXEC))
794 prot |= PROT_EXEC;
795
796 /*
797 * Each mprotect() call explicitly passes r/w/x permissions.
798 * If a permission is not passed to mprotect(), it must be
799 * cleared from the VMA.
800 */
801 mask_off_old_flags = VM_ACCESS_FLAGS | VM_FLAGS_CLEAR;
802
803 new_vma_pkey = arch_override_mprotect_pkey(vma, prot, pkey);
804 newflags = calc_vm_prot_bits(prot, new_vma_pkey);
805 newflags |= (vma->vm_flags & ~mask_off_old_flags);
806
807 /* newflags >> 4 shift VM_MAY% in place of VM_% */
808 if ((newflags & ~(newflags >> 4)) & VM_ACCESS_FLAGS) {
809 error = -EACCES;
810 break;
811 }
812
813 if (map_deny_write_exec(vma->vm_flags, newflags)) {
814 error = -EACCES;
815 break;
816 }
817
818 /* Allow architectures to sanity-check the new flags */
819 if (!arch_validate_flags(newflags)) {
820 error = -EINVAL;
821 break;
822 }
823
824 error = security_file_mprotect(vma, reqprot, prot);
825 if (error)
826 break;
827
828 tmp = vma->vm_end;
829 if (tmp > end)
830 tmp = end;
831
832 if (vma->vm_ops && vma->vm_ops->mprotect) {
833 error = vma->vm_ops->mprotect(vma, nstart, tmp, newflags);
834 if (error)
835 break;
836 }
837
838 error = mprotect_fixup(&vmi, &tlb, vma, &prev, nstart, tmp, newflags);
839 if (error)
840 break;
841
842 tmp = vma_iter_end(&vmi);
843 nstart = tmp;
844 prot = reqprot;
845 }
846 tlb_finish_mmu(&tlb);
847
848 if (!error && tmp < end)
849 error = -ENOMEM;
850
851 out:
852 mmap_write_unlock(current->mm);
853 return error;
854 }
855
SYSCALL_DEFINE3(mprotect,unsigned long,start,size_t,len,unsigned long,prot)856 SYSCALL_DEFINE3(mprotect, unsigned long, start, size_t, len,
857 unsigned long, prot)
858 {
859 return do_mprotect_pkey(start, len, prot, -1);
860 }
861
862 #ifdef CONFIG_ARCH_HAS_PKEYS
863
SYSCALL_DEFINE4(pkey_mprotect,unsigned long,start,size_t,len,unsigned long,prot,int,pkey)864 SYSCALL_DEFINE4(pkey_mprotect, unsigned long, start, size_t, len,
865 unsigned long, prot, int, pkey)
866 {
867 return do_mprotect_pkey(start, len, prot, pkey);
868 }
869
SYSCALL_DEFINE2(pkey_alloc,unsigned long,flags,unsigned long,init_val)870 SYSCALL_DEFINE2(pkey_alloc, unsigned long, flags, unsigned long, init_val)
871 {
872 int pkey;
873 int ret;
874
875 /* No flags supported yet. */
876 if (flags)
877 return -EINVAL;
878 /* check for unsupported init values */
879 if (init_val & ~PKEY_ACCESS_MASK)
880 return -EINVAL;
881
882 mmap_write_lock(current->mm);
883 pkey = mm_pkey_alloc(current->mm);
884
885 ret = -ENOSPC;
886 if (pkey == -1)
887 goto out;
888
889 ret = arch_set_user_pkey_access(current, pkey, init_val);
890 if (ret) {
891 mm_pkey_free(current->mm, pkey);
892 goto out;
893 }
894 ret = pkey;
895 out:
896 mmap_write_unlock(current->mm);
897 return ret;
898 }
899
SYSCALL_DEFINE1(pkey_free,int,pkey)900 SYSCALL_DEFINE1(pkey_free, int, pkey)
901 {
902 int ret;
903
904 mmap_write_lock(current->mm);
905 ret = mm_pkey_free(current->mm, pkey);
906 mmap_write_unlock(current->mm);
907
908 /*
909 * We could provide warnings or errors if any VMA still
910 * has the pkey set here.
911 */
912 return ret;
913 }
914
915 #endif /* CONFIG_ARCH_HAS_PKEYS */
916