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1 | /* | |
2 | * mm/mprotect.c | |
3 | * | |
4 | * (C) Copyright 1994 Linus Torvalds | |
5 | * (C) Copyright 2002 Christoph Hellwig | |
6 | * | |
7 | * Address space accounting code <alan@lxorguk.ukuu.org.uk> | |
8 | * (C) Copyright 2002 Red Hat Inc, All Rights Reserved | |
9 | */ | |
10 | ||
11 | #include <linux/mm.h> | |
12 | #include <linux/hugetlb.h> | |
13 | #include <linux/shm.h> | |
14 | #include <linux/mman.h> | |
15 | #include <linux/fs.h> | |
16 | #include <linux/highmem.h> | |
17 | #include <linux/security.h> | |
18 | #include <linux/mempolicy.h> | |
19 | #include <linux/personality.h> | |
20 | #include <linux/syscalls.h> | |
21 | #include <linux/swap.h> | |
22 | #include <linux/swapops.h> | |
23 | #include <linux/mmu_notifier.h> | |
24 | #include <linux/migrate.h> | |
25 | #include <linux/perf_event.h> | |
26 | #include <linux/pkeys.h> | |
27 | #include <linux/ksm.h> | |
28 | #include <linux/uaccess.h> | |
29 | #include <asm/pgtable.h> | |
30 | #include <asm/cacheflush.h> | |
31 | #include <asm/mmu_context.h> | |
32 | #include <asm/tlbflush.h> | |
33 | ||
34 | #include "internal.h" | |
35 | ||
36 | static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd, | |
37 | unsigned long addr, unsigned long end, pgprot_t newprot, | |
38 | int dirty_accountable, int prot_numa) | |
39 | { | |
40 | struct mm_struct *mm = vma->vm_mm; | |
41 | pte_t *pte, oldpte; | |
42 | spinlock_t *ptl; | |
43 | unsigned long pages = 0; | |
44 | int target_node = NUMA_NO_NODE; | |
45 | ||
46 | /* | |
47 | * Can be called with only the mmap_sem for reading by | |
48 | * prot_numa so we must check the pmd isn't constantly | |
49 | * changing from under us from pmd_none to pmd_trans_huge | |
50 | * and/or the other way around. | |
51 | */ | |
52 | if (pmd_trans_unstable(pmd)) | |
53 | return 0; | |
54 | ||
55 | /* | |
56 | * The pmd points to a regular pte so the pmd can't change | |
57 | * from under us even if the mmap_sem is only hold for | |
58 | * reading. | |
59 | */ | |
60 | pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); | |
61 | ||
62 | /* Get target node for single threaded private VMAs */ | |
63 | if (prot_numa && !(vma->vm_flags & VM_SHARED) && | |
64 | atomic_read(&vma->vm_mm->mm_users) == 1) | |
65 | target_node = numa_node_id(); | |
66 | ||
67 | flush_tlb_batched_pending(vma->vm_mm); | |
68 | arch_enter_lazy_mmu_mode(); | |
69 | do { | |
70 | oldpte = *pte; | |
71 | if (pte_present(oldpte)) { | |
72 | pte_t ptent; | |
73 | bool preserve_write = prot_numa && pte_write(oldpte); | |
74 | ||
75 | /* | |
76 | * Avoid trapping faults against the zero or KSM | |
77 | * pages. See similar comment in change_huge_pmd. | |
78 | */ | |
79 | if (prot_numa) { | |
80 | struct page *page; | |
81 | ||
82 | page = vm_normal_page(vma, addr, oldpte); | |
83 | if (!page || PageKsm(page)) | |
84 | continue; | |
85 | ||
86 | /* Avoid TLB flush if possible */ | |
87 | if (pte_protnone(oldpte)) | |
88 | continue; | |
89 | ||
90 | /* | |
91 | * Don't mess with PTEs if page is already on the node | |
92 | * a single-threaded process is running on. | |
93 | */ | |
94 | if (target_node == page_to_nid(page)) | |
95 | continue; | |
96 | } | |
97 | ||
98 | ptent = ptep_modify_prot_start(mm, addr, pte); | |
99 | ptent = pte_modify(ptent, newprot); | |
100 | if (preserve_write) | |
101 | ptent = pte_mk_savedwrite(ptent); | |
102 | ||
103 | /* Avoid taking write faults for known dirty pages */ | |
104 | if (dirty_accountable && pte_dirty(ptent) && | |
105 | (pte_soft_dirty(ptent) || | |
106 | !(vma->vm_flags & VM_SOFTDIRTY))) { | |
107 | ptent = pte_mkwrite(ptent); | |
108 | } | |
109 | ptep_modify_prot_commit(mm, addr, pte, ptent); | |
110 | pages++; | |
111 | } else if (IS_ENABLED(CONFIG_MIGRATION)) { | |
112 | swp_entry_t entry = pte_to_swp_entry(oldpte); | |
113 | ||
114 | if (is_write_migration_entry(entry)) { | |
115 | pte_t newpte; | |
116 | /* | |
117 | * A protection check is difficult so | |
118 | * just be safe and disable write | |
119 | */ | |
120 | make_migration_entry_read(&entry); | |
121 | newpte = swp_entry_to_pte(entry); | |
122 | if (pte_swp_soft_dirty(oldpte)) | |
123 | newpte = pte_swp_mksoft_dirty(newpte); | |
124 | set_pte_at(mm, addr, pte, newpte); | |
125 | ||
126 | pages++; | |
127 | } | |
128 | } | |
129 | } while (pte++, addr += PAGE_SIZE, addr != end); | |
130 | arch_leave_lazy_mmu_mode(); | |
131 | pte_unmap_unlock(pte - 1, ptl); | |
132 | ||
133 | return pages; | |
134 | } | |
135 | ||
136 | static inline unsigned long change_pmd_range(struct vm_area_struct *vma, | |
137 | pud_t *pud, unsigned long addr, unsigned long end, | |
138 | pgprot_t newprot, int dirty_accountable, int prot_numa) | |
139 | { | |
140 | pmd_t *pmd; | |
141 | struct mm_struct *mm = vma->vm_mm; | |
142 | unsigned long next; | |
143 | unsigned long pages = 0; | |
144 | unsigned long nr_huge_updates = 0; | |
145 | unsigned long mni_start = 0; | |
146 | ||
147 | pmd = pmd_offset(pud, addr); | |
148 | do { | |
149 | unsigned long this_pages; | |
150 | ||
151 | next = pmd_addr_end(addr, end); | |
152 | if (!pmd_trans_huge(*pmd) && !pmd_devmap(*pmd) | |
153 | && pmd_none_or_clear_bad(pmd)) | |
154 | continue; | |
155 | ||
156 | /* invoke the mmu notifier if the pmd is populated */ | |
157 | if (!mni_start) { | |
158 | mni_start = addr; | |
159 | mmu_notifier_invalidate_range_start(mm, mni_start, end); | |
160 | } | |
161 | ||
162 | if (pmd_trans_huge(*pmd) || pmd_devmap(*pmd)) { | |
163 | if (next - addr != HPAGE_PMD_SIZE) { | |
164 | __split_huge_pmd(vma, pmd, addr, false, NULL); | |
165 | } else { | |
166 | int nr_ptes = change_huge_pmd(vma, pmd, addr, | |
167 | newprot, prot_numa); | |
168 | ||
169 | if (nr_ptes) { | |
170 | if (nr_ptes == HPAGE_PMD_NR) { | |
171 | pages += HPAGE_PMD_NR; | |
172 | nr_huge_updates++; | |
173 | } | |
174 | ||
175 | /* huge pmd was handled */ | |
176 | continue; | |
177 | } | |
178 | } | |
179 | /* fall through, the trans huge pmd just split */ | |
180 | } | |
181 | this_pages = change_pte_range(vma, pmd, addr, next, newprot, | |
182 | dirty_accountable, prot_numa); | |
183 | pages += this_pages; | |
184 | } while (pmd++, addr = next, addr != end); | |
185 | ||
186 | if (mni_start) | |
187 | mmu_notifier_invalidate_range_end(mm, mni_start, end); | |
188 | ||
189 | if (nr_huge_updates) | |
190 | count_vm_numa_events(NUMA_HUGE_PTE_UPDATES, nr_huge_updates); | |
191 | return pages; | |
192 | } | |
193 | ||
194 | static inline unsigned long change_pud_range(struct vm_area_struct *vma, | |
195 | p4d_t *p4d, unsigned long addr, unsigned long end, | |
196 | pgprot_t newprot, int dirty_accountable, int prot_numa) | |
197 | { | |
198 | pud_t *pud; | |
199 | unsigned long next; | |
200 | unsigned long pages = 0; | |
201 | ||
202 | pud = pud_offset(p4d, addr); | |
203 | do { | |
204 | next = pud_addr_end(addr, end); | |
205 | if (pud_none_or_clear_bad(pud)) | |
206 | continue; | |
207 | pages += change_pmd_range(vma, pud, addr, next, newprot, | |
208 | dirty_accountable, prot_numa); | |
209 | } while (pud++, addr = next, addr != end); | |
210 | ||
211 | return pages; | |
212 | } | |
213 | ||
214 | static inline unsigned long change_p4d_range(struct vm_area_struct *vma, | |
215 | pgd_t *pgd, unsigned long addr, unsigned long end, | |
216 | pgprot_t newprot, int dirty_accountable, int prot_numa) | |
217 | { | |
218 | p4d_t *p4d; | |
219 | unsigned long next; | |
220 | unsigned long pages = 0; | |
221 | ||
222 | p4d = p4d_offset(pgd, addr); | |
223 | do { | |
224 | next = p4d_addr_end(addr, end); | |
225 | if (p4d_none_or_clear_bad(p4d)) | |
226 | continue; | |
227 | pages += change_pud_range(vma, p4d, addr, next, newprot, | |
228 | dirty_accountable, prot_numa); | |
229 | } while (p4d++, addr = next, addr != end); | |
230 | ||
231 | return pages; | |
232 | } | |
233 | ||
234 | static unsigned long change_protection_range(struct vm_area_struct *vma, | |
235 | unsigned long addr, unsigned long end, pgprot_t newprot, | |
236 | int dirty_accountable, int prot_numa) | |
237 | { | |
238 | struct mm_struct *mm = vma->vm_mm; | |
239 | pgd_t *pgd; | |
240 | unsigned long next; | |
241 | unsigned long start = addr; | |
242 | unsigned long pages = 0; | |
243 | ||
244 | BUG_ON(addr >= end); | |
245 | pgd = pgd_offset(mm, addr); | |
246 | flush_cache_range(vma, addr, end); | |
247 | inc_tlb_flush_pending(mm); | |
248 | do { | |
249 | next = pgd_addr_end(addr, end); | |
250 | if (pgd_none_or_clear_bad(pgd)) | |
251 | continue; | |
252 | pages += change_p4d_range(vma, pgd, addr, next, newprot, | |
253 | dirty_accountable, prot_numa); | |
254 | } while (pgd++, addr = next, addr != end); | |
255 | ||
256 | /* Only flush the TLB if we actually modified any entries: */ | |
257 | if (pages) | |
258 | flush_tlb_range(vma, start, end); | |
259 | dec_tlb_flush_pending(mm); | |
260 | ||
261 | return pages; | |
262 | } | |
263 | ||
264 | unsigned long change_protection(struct vm_area_struct *vma, unsigned long start, | |
265 | unsigned long end, pgprot_t newprot, | |
266 | int dirty_accountable, int prot_numa) | |
267 | { | |
268 | unsigned long pages; | |
269 | ||
270 | if (is_vm_hugetlb_page(vma)) | |
271 | pages = hugetlb_change_protection(vma, start, end, newprot); | |
272 | else | |
273 | pages = change_protection_range(vma, start, end, newprot, dirty_accountable, prot_numa); | |
274 | ||
275 | return pages; | |
276 | } | |
277 | ||
278 | int | |
279 | mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev, | |
280 | unsigned long start, unsigned long end, unsigned long newflags) | |
281 | { | |
282 | struct mm_struct *mm = vma->vm_mm; | |
283 | unsigned long oldflags = vma->vm_flags; | |
284 | long nrpages = (end - start) >> PAGE_SHIFT; | |
285 | unsigned long charged = 0; | |
286 | pgoff_t pgoff; | |
287 | int error; | |
288 | int dirty_accountable = 0; | |
289 | ||
290 | if (newflags == oldflags) { | |
291 | *pprev = vma; | |
292 | return 0; | |
293 | } | |
294 | ||
295 | /* | |
296 | * If we make a private mapping writable we increase our commit; | |
297 | * but (without finer accounting) cannot reduce our commit if we | |
298 | * make it unwritable again. hugetlb mapping were accounted for | |
299 | * even if read-only so there is no need to account for them here | |
300 | */ | |
301 | if (newflags & VM_WRITE) { | |
302 | /* Check space limits when area turns into data. */ | |
303 | if (!may_expand_vm(mm, newflags, nrpages) && | |
304 | may_expand_vm(mm, oldflags, nrpages)) | |
305 | return -ENOMEM; | |
306 | if (!(oldflags & (VM_ACCOUNT|VM_WRITE|VM_HUGETLB| | |
307 | VM_SHARED|VM_NORESERVE))) { | |
308 | charged = nrpages; | |
309 | if (security_vm_enough_memory_mm(mm, charged)) | |
310 | return -ENOMEM; | |
311 | newflags |= VM_ACCOUNT; | |
312 | } | |
313 | } | |
314 | ||
315 | /* | |
316 | * First try to merge with previous and/or next vma. | |
317 | */ | |
318 | pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT); | |
319 | *pprev = vma_merge(mm, *pprev, start, end, newflags, | |
320 | vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma), | |
321 | vma->vm_userfaultfd_ctx); | |
322 | if (*pprev) { | |
323 | vma = *pprev; | |
324 | VM_WARN_ON((vma->vm_flags ^ newflags) & ~VM_SOFTDIRTY); | |
325 | goto success; | |
326 | } | |
327 | ||
328 | *pprev = vma; | |
329 | ||
330 | if (start != vma->vm_start) { | |
331 | error = split_vma(mm, vma, start, 1); | |
332 | if (error) | |
333 | goto fail; | |
334 | } | |
335 | ||
336 | if (end != vma->vm_end) { | |
337 | error = split_vma(mm, vma, end, 0); | |
338 | if (error) | |
339 | goto fail; | |
340 | } | |
341 | ||
342 | success: | |
343 | /* | |
344 | * vm_flags and vm_page_prot are protected by the mmap_sem | |
345 | * held in write mode. | |
346 | */ | |
347 | vma->vm_flags = newflags; | |
348 | dirty_accountable = vma_wants_writenotify(vma, vma->vm_page_prot); | |
349 | vma_set_page_prot(vma); | |
350 | ||
351 | change_protection(vma, start, end, vma->vm_page_prot, | |
352 | dirty_accountable, 0); | |
353 | ||
354 | /* | |
355 | * Private VM_LOCKED VMA becoming writable: trigger COW to avoid major | |
356 | * fault on access. | |
357 | */ | |
358 | if ((oldflags & (VM_WRITE | VM_SHARED | VM_LOCKED)) == VM_LOCKED && | |
359 | (newflags & VM_WRITE)) { | |
360 | populate_vma_page_range(vma, start, end, NULL); | |
361 | } | |
362 | ||
363 | vm_stat_account(mm, oldflags, -nrpages); | |
364 | vm_stat_account(mm, newflags, nrpages); | |
365 | perf_event_mmap(vma); | |
366 | return 0; | |
367 | ||
368 | fail: | |
369 | vm_unacct_memory(charged); | |
370 | return error; | |
371 | } | |
372 | ||
373 | /* | |
374 | * pkey==-1 when doing a legacy mprotect() | |
375 | */ | |
376 | static int do_mprotect_pkey(unsigned long start, size_t len, | |
377 | unsigned long prot, int pkey) | |
378 | { | |
379 | unsigned long nstart, end, tmp, reqprot; | |
380 | struct vm_area_struct *vma, *prev; | |
381 | int error = -EINVAL; | |
382 | const int grows = prot & (PROT_GROWSDOWN|PROT_GROWSUP); | |
383 | const bool rier = (current->personality & READ_IMPLIES_EXEC) && | |
384 | (prot & PROT_READ); | |
385 | ||
386 | prot &= ~(PROT_GROWSDOWN|PROT_GROWSUP); | |
387 | if (grows == (PROT_GROWSDOWN|PROT_GROWSUP)) /* can't be both */ | |
388 | return -EINVAL; | |
389 | ||
390 | if (start & ~PAGE_MASK) | |
391 | return -EINVAL; | |
392 | if (!len) | |
393 | return 0; | |
394 | len = PAGE_ALIGN(len); | |
395 | end = start + len; | |
396 | if (end <= start) | |
397 | return -ENOMEM; | |
398 | if (!arch_validate_prot(prot)) | |
399 | return -EINVAL; | |
400 | ||
401 | reqprot = prot; | |
402 | ||
403 | if (down_write_killable(¤t->mm->mmap_sem)) | |
404 | return -EINTR; | |
405 | ||
406 | /* | |
407 | * If userspace did not allocate the pkey, do not let | |
408 | * them use it here. | |
409 | */ | |
410 | error = -EINVAL; | |
411 | if ((pkey != -1) && !mm_pkey_is_allocated(current->mm, pkey)) | |
412 | goto out; | |
413 | ||
414 | vma = find_vma(current->mm, start); | |
415 | error = -ENOMEM; | |
416 | if (!vma) | |
417 | goto out; | |
418 | prev = vma->vm_prev; | |
419 | if (unlikely(grows & PROT_GROWSDOWN)) { | |
420 | if (vma->vm_start >= end) | |
421 | goto out; | |
422 | start = vma->vm_start; | |
423 | error = -EINVAL; | |
424 | if (!(vma->vm_flags & VM_GROWSDOWN)) | |
425 | goto out; | |
426 | } else { | |
427 | if (vma->vm_start > start) | |
428 | goto out; | |
429 | if (unlikely(grows & PROT_GROWSUP)) { | |
430 | end = vma->vm_end; | |
431 | error = -EINVAL; | |
432 | if (!(vma->vm_flags & VM_GROWSUP)) | |
433 | goto out; | |
434 | } | |
435 | } | |
436 | if (start > vma->vm_start) | |
437 | prev = vma; | |
438 | ||
439 | for (nstart = start ; ; ) { | |
440 | unsigned long mask_off_old_flags; | |
441 | unsigned long newflags; | |
442 | int new_vma_pkey; | |
443 | ||
444 | /* Here we know that vma->vm_start <= nstart < vma->vm_end. */ | |
445 | ||
446 | /* Does the application expect PROT_READ to imply PROT_EXEC */ | |
447 | if (rier && (vma->vm_flags & VM_MAYEXEC)) | |
448 | prot |= PROT_EXEC; | |
449 | ||
450 | /* | |
451 | * Each mprotect() call explicitly passes r/w/x permissions. | |
452 | * If a permission is not passed to mprotect(), it must be | |
453 | * cleared from the VMA. | |
454 | */ | |
455 | mask_off_old_flags = VM_READ | VM_WRITE | VM_EXEC | | |
456 | ARCH_VM_PKEY_FLAGS; | |
457 | ||
458 | new_vma_pkey = arch_override_mprotect_pkey(vma, prot, pkey); | |
459 | newflags = calc_vm_prot_bits(prot, new_vma_pkey); | |
460 | newflags |= (vma->vm_flags & ~mask_off_old_flags); | |
461 | ||
462 | /* newflags >> 4 shift VM_MAY% in place of VM_% */ | |
463 | if ((newflags & ~(newflags >> 4)) & (VM_READ | VM_WRITE | VM_EXEC)) { | |
464 | error = -EACCES; | |
465 | goto out; | |
466 | } | |
467 | ||
468 | error = security_file_mprotect(vma, reqprot, prot); | |
469 | if (error) | |
470 | goto out; | |
471 | ||
472 | tmp = vma->vm_end; | |
473 | if (tmp > end) | |
474 | tmp = end; | |
475 | error = mprotect_fixup(vma, &prev, nstart, tmp, newflags); | |
476 | if (error) | |
477 | goto out; | |
478 | nstart = tmp; | |
479 | ||
480 | if (nstart < prev->vm_end) | |
481 | nstart = prev->vm_end; | |
482 | if (nstart >= end) | |
483 | goto out; | |
484 | ||
485 | vma = prev->vm_next; | |
486 | if (!vma || vma->vm_start != nstart) { | |
487 | error = -ENOMEM; | |
488 | goto out; | |
489 | } | |
490 | prot = reqprot; | |
491 | } | |
492 | out: | |
493 | up_write(¤t->mm->mmap_sem); | |
494 | return error; | |
495 | } | |
496 | ||
497 | SYSCALL_DEFINE3(mprotect, unsigned long, start, size_t, len, | |
498 | unsigned long, prot) | |
499 | { | |
500 | return do_mprotect_pkey(start, len, prot, -1); | |
501 | } | |
502 | ||
503 | #ifdef CONFIG_ARCH_HAS_PKEYS | |
504 | ||
505 | SYSCALL_DEFINE4(pkey_mprotect, unsigned long, start, size_t, len, | |
506 | unsigned long, prot, int, pkey) | |
507 | { | |
508 | return do_mprotect_pkey(start, len, prot, pkey); | |
509 | } | |
510 | ||
511 | SYSCALL_DEFINE2(pkey_alloc, unsigned long, flags, unsigned long, init_val) | |
512 | { | |
513 | int pkey; | |
514 | int ret; | |
515 | ||
516 | /* No flags supported yet. */ | |
517 | if (flags) | |
518 | return -EINVAL; | |
519 | /* check for unsupported init values */ | |
520 | if (init_val & ~PKEY_ACCESS_MASK) | |
521 | return -EINVAL; | |
522 | ||
523 | down_write(¤t->mm->mmap_sem); | |
524 | pkey = mm_pkey_alloc(current->mm); | |
525 | ||
526 | ret = -ENOSPC; | |
527 | if (pkey == -1) | |
528 | goto out; | |
529 | ||
530 | ret = arch_set_user_pkey_access(current, pkey, init_val); | |
531 | if (ret) { | |
532 | mm_pkey_free(current->mm, pkey); | |
533 | goto out; | |
534 | } | |
535 | ret = pkey; | |
536 | out: | |
537 | up_write(¤t->mm->mmap_sem); | |
538 | return ret; | |
539 | } | |
540 | ||
541 | SYSCALL_DEFINE1(pkey_free, int, pkey) | |
542 | { | |
543 | int ret; | |
544 | ||
545 | down_write(¤t->mm->mmap_sem); | |
546 | ret = mm_pkey_free(current->mm, pkey); | |
547 | up_write(¤t->mm->mmap_sem); | |
548 | ||
549 | /* | |
550 | * We could provie warnings or errors if any VMA still | |
551 | * has the pkey set here. | |
552 | */ | |
553 | return ret; | |
554 | } | |
555 | ||
556 | #endif /* CONFIG_ARCH_HAS_PKEYS */ |