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