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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/ksm.h> | |
27 | #include <linux/pkeys.h> | |
28 | #include <asm/uaccess.h> | |
29 | #include <asm/pgtable.h> | |
30 | #include <asm/cacheflush.h> | |
31 | #include <asm/tlbflush.h> | |
32 | ||
33 | #include "internal.h" | |
34 | ||
35 | /* | |
36 | * For a prot_numa update we only hold mmap_sem for read so there is a | |
37 | * potential race with faulting where a pmd was temporarily none. This | |
38 | * function checks for a transhuge pmd under the appropriate lock. It | |
39 | * returns a pte if it was successfully locked or NULL if it raced with | |
40 | * a transhuge insertion. | |
41 | */ | |
42 | static pte_t *lock_pte_protection(struct vm_area_struct *vma, pmd_t *pmd, | |
43 | unsigned long addr, int prot_numa, spinlock_t **ptl) | |
44 | { | |
45 | pte_t *pte; | |
46 | spinlock_t *pmdl; | |
47 | ||
48 | /* !prot_numa is protected by mmap_sem held for write */ | |
49 | if (!prot_numa) | |
50 | return pte_offset_map_lock(vma->vm_mm, pmd, addr, ptl); | |
51 | ||
52 | pmdl = pmd_lock(vma->vm_mm, pmd); | |
53 | if (unlikely(pmd_trans_huge(*pmd) || pmd_none(*pmd))) { | |
54 | spin_unlock(pmdl); | |
55 | return NULL; | |
56 | } | |
57 | ||
58 | pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, ptl); | |
59 | spin_unlock(pmdl); | |
60 | return pte; | |
61 | } | |
62 | ||
63 | static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd, | |
64 | unsigned long addr, unsigned long end, pgprot_t newprot, | |
65 | int dirty_accountable, int prot_numa) | |
66 | { | |
67 | struct mm_struct *mm = vma->vm_mm; | |
68 | pte_t *pte, oldpte; | |
69 | spinlock_t *ptl; | |
70 | unsigned long pages = 0; | |
71 | ||
72 | pte = lock_pte_protection(vma, pmd, addr, prot_numa, &ptl); | |
73 | if (!pte) | |
74 | return 0; | |
75 | ||
76 | arch_enter_lazy_mmu_mode(); | |
77 | do { | |
78 | oldpte = *pte; | |
79 | if (pte_present(oldpte)) { | |
80 | pte_t ptent; | |
81 | bool preserve_write = prot_numa && pte_write(oldpte); | |
82 | ||
83 | /* | |
84 | * Avoid trapping faults against the zero or KSM | |
85 | * pages. See similar comment in change_huge_pmd. | |
86 | */ | |
87 | if (prot_numa) { | |
88 | struct page *page; | |
89 | ||
90 | page = vm_normal_page(vma, addr, oldpte); | |
91 | if (!page || PageKsm(page)) | |
92 | continue; | |
93 | ||
94 | /* Avoid TLB flush if possible */ | |
95 | if (pte_protnone(oldpte)) | |
96 | continue; | |
97 | } | |
98 | ||
99 | ptent = ptep_modify_prot_start(mm, addr, pte); | |
100 | ptent = pte_modify(ptent, newprot); | |
101 | if (preserve_write) | |
102 | ptent = pte_mkwrite(ptent); | |
103 | ||
104 | /* Avoid taking write faults for known dirty pages */ | |
105 | if (dirty_accountable && pte_dirty(ptent) && | |
106 | (pte_soft_dirty(ptent) || | |
107 | !(vma->vm_flags & VM_SOFTDIRTY))) { | |
108 | ptent = pte_mkwrite(ptent); | |
109 | } | |
110 | ptep_modify_prot_commit(mm, addr, pte, ptent); | |
111 | pages++; | |
112 | } else if (IS_ENABLED(CONFIG_MIGRATION)) { | |
113 | swp_entry_t entry = pte_to_swp_entry(oldpte); | |
114 | ||
115 | if (is_write_migration_entry(entry)) { | |
116 | pte_t newpte; | |
117 | /* | |
118 | * A protection check is difficult so | |
119 | * just be safe and disable write | |
120 | */ | |
121 | make_migration_entry_read(&entry); | |
122 | newpte = swp_entry_to_pte(entry); | |
123 | if (pte_swp_soft_dirty(oldpte)) | |
124 | newpte = pte_swp_mksoft_dirty(newpte); | |
125 | set_pte_at(mm, addr, pte, newpte); | |
126 | ||
127 | pages++; | |
128 | } | |
129 | } | |
130 | } while (pte++, addr += PAGE_SIZE, addr != end); | |
131 | arch_leave_lazy_mmu_mode(); | |
132 | pte_unmap_unlock(pte - 1, ptl); | |
133 | ||
134 | return pages; | |
135 | } | |
136 | ||
137 | static inline unsigned long change_pmd_range(struct vm_area_struct *vma, | |
138 | pud_t *pud, unsigned long addr, unsigned long end, | |
139 | pgprot_t newprot, int dirty_accountable, int prot_numa) | |
140 | { | |
141 | pmd_t *pmd; | |
142 | struct mm_struct *mm = vma->vm_mm; | |
143 | unsigned long next; | |
144 | unsigned long pages = 0; | |
145 | unsigned long nr_huge_updates = 0; | |
146 | unsigned long mni_start = 0; | |
147 | ||
148 | pmd = pmd_offset(pud, addr); | |
149 | do { | |
150 | unsigned long this_pages; | |
151 | ||
152 | next = pmd_addr_end(addr, end); | |
153 | if (!pmd_trans_huge(*pmd) && !pmd_devmap(*pmd) | |
154 | && pmd_none_or_clear_bad(pmd)) | |
155 | continue; | |
156 | ||
157 | /* invoke the mmu notifier if the pmd is populated */ | |
158 | if (!mni_start) { | |
159 | mni_start = addr; | |
160 | mmu_notifier_invalidate_range_start(mm, mni_start, end); | |
161 | } | |
162 | ||
163 | if (pmd_trans_huge(*pmd) || pmd_devmap(*pmd)) { | |
164 | if (next - addr != HPAGE_PMD_SIZE) { | |
165 | split_huge_pmd(vma, pmd, addr); | |
166 | if (pmd_trans_unstable(pmd)) | |
167 | continue; | |
168 | } else { | |
169 | int nr_ptes = change_huge_pmd(vma, pmd, addr, | |
170 | newprot, prot_numa); | |
171 | ||
172 | if (nr_ptes) { | |
173 | if (nr_ptes == HPAGE_PMD_NR) { | |
174 | pages += HPAGE_PMD_NR; | |
175 | nr_huge_updates++; | |
176 | } | |
177 | ||
178 | /* huge pmd was handled */ | |
179 | continue; | |
180 | } | |
181 | } | |
182 | /* fall through, the trans huge pmd just split */ | |
183 | } | |
184 | this_pages = change_pte_range(vma, pmd, addr, next, newprot, | |
185 | dirty_accountable, prot_numa); | |
186 | pages += this_pages; | |
187 | } while (pmd++, addr = next, addr != end); | |
188 | ||
189 | if (mni_start) | |
190 | mmu_notifier_invalidate_range_end(mm, mni_start, end); | |
191 | ||
192 | if (nr_huge_updates) | |
193 | count_vm_numa_events(NUMA_HUGE_PTE_UPDATES, nr_huge_updates); | |
194 | return pages; | |
195 | } | |
196 | ||
197 | static inline unsigned long change_pud_range(struct vm_area_struct *vma, | |
198 | pgd_t *pgd, unsigned long addr, unsigned long end, | |
199 | pgprot_t newprot, int dirty_accountable, int prot_numa) | |
200 | { | |
201 | pud_t *pud; | |
202 | unsigned long next; | |
203 | unsigned long pages = 0; | |
204 | ||
205 | pud = pud_offset(pgd, addr); | |
206 | do { | |
207 | next = pud_addr_end(addr, end); | |
208 | if (pud_none_or_clear_bad(pud)) | |
209 | continue; | |
210 | pages += change_pmd_range(vma, pud, addr, next, newprot, | |
211 | dirty_accountable, prot_numa); | |
212 | } while (pud++, addr = next, addr != end); | |
213 | ||
214 | return pages; | |
215 | } | |
216 | ||
217 | static unsigned long change_protection_range(struct vm_area_struct *vma, | |
218 | unsigned long addr, unsigned long end, pgprot_t newprot, | |
219 | int dirty_accountable, int prot_numa) | |
220 | { | |
221 | struct mm_struct *mm = vma->vm_mm; | |
222 | pgd_t *pgd; | |
223 | unsigned long next; | |
224 | unsigned long start = addr; | |
225 | unsigned long pages = 0; | |
226 | ||
227 | BUG_ON(addr >= end); | |
228 | pgd = pgd_offset(mm, addr); | |
229 | flush_cache_range(vma, addr, end); | |
230 | set_tlb_flush_pending(mm); | |
231 | do { | |
232 | next = pgd_addr_end(addr, end); | |
233 | if (pgd_none_or_clear_bad(pgd)) | |
234 | continue; | |
235 | pages += change_pud_range(vma, pgd, addr, next, newprot, | |
236 | dirty_accountable, prot_numa); | |
237 | } while (pgd++, addr = next, addr != end); | |
238 | ||
239 | /* Only flush the TLB if we actually modified any entries: */ | |
240 | if (pages) | |
241 | flush_tlb_range(vma, start, end); | |
242 | clear_tlb_flush_pending(mm); | |
243 | ||
244 | return pages; | |
245 | } | |
246 | ||
247 | unsigned long change_protection(struct vm_area_struct *vma, unsigned long start, | |
248 | unsigned long end, pgprot_t newprot, | |
249 | int dirty_accountable, int prot_numa) | |
250 | { | |
251 | unsigned long pages; | |
252 | ||
253 | if (is_vm_hugetlb_page(vma)) | |
254 | pages = hugetlb_change_protection(vma, start, end, newprot); | |
255 | else | |
256 | pages = change_protection_range(vma, start, end, newprot, dirty_accountable, prot_numa); | |
257 | ||
258 | return pages; | |
259 | } | |
260 | ||
261 | int | |
262 | mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev, | |
263 | unsigned long start, unsigned long end, unsigned long newflags) | |
264 | { | |
265 | struct mm_struct *mm = vma->vm_mm; | |
266 | unsigned long oldflags = vma->vm_flags; | |
267 | long nrpages = (end - start) >> PAGE_SHIFT; | |
268 | unsigned long charged = 0; | |
269 | pgoff_t pgoff; | |
270 | int error; | |
271 | int dirty_accountable = 0; | |
272 | ||
273 | if (newflags == oldflags) { | |
274 | *pprev = vma; | |
275 | return 0; | |
276 | } | |
277 | ||
278 | /* | |
279 | * If we make a private mapping writable we increase our commit; | |
280 | * but (without finer accounting) cannot reduce our commit if we | |
281 | * make it unwritable again. hugetlb mapping were accounted for | |
282 | * even if read-only so there is no need to account for them here | |
283 | */ | |
284 | if (newflags & VM_WRITE) { | |
285 | /* Check space limits when area turns into data. */ | |
286 | if (!may_expand_vm(mm, newflags, nrpages) && | |
287 | may_expand_vm(mm, oldflags, nrpages)) | |
288 | return -ENOMEM; | |
289 | if (!(oldflags & (VM_ACCOUNT|VM_WRITE|VM_HUGETLB| | |
290 | VM_SHARED|VM_NORESERVE))) { | |
291 | charged = nrpages; | |
292 | if (security_vm_enough_memory_mm(mm, charged)) | |
293 | return -ENOMEM; | |
294 | newflags |= VM_ACCOUNT; | |
295 | } | |
296 | } | |
297 | ||
298 | /* | |
299 | * First try to merge with previous and/or next vma. | |
300 | */ | |
301 | pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT); | |
302 | *pprev = vma_merge(mm, *pprev, start, end, newflags, | |
303 | vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma), | |
304 | vma->vm_userfaultfd_ctx); | |
305 | if (*pprev) { | |
306 | vma = *pprev; | |
307 | goto success; | |
308 | } | |
309 | ||
310 | *pprev = vma; | |
311 | ||
312 | if (start != vma->vm_start) { | |
313 | error = split_vma(mm, vma, start, 1); | |
314 | if (error) | |
315 | goto fail; | |
316 | } | |
317 | ||
318 | if (end != vma->vm_end) { | |
319 | error = split_vma(mm, vma, end, 0); | |
320 | if (error) | |
321 | goto fail; | |
322 | } | |
323 | ||
324 | success: | |
325 | /* | |
326 | * vm_flags and vm_page_prot are protected by the mmap_sem | |
327 | * held in write mode. | |
328 | */ | |
329 | vma->vm_flags = newflags; | |
330 | dirty_accountable = vma_wants_writenotify(vma); | |
331 | vma_set_page_prot(vma); | |
332 | ||
333 | change_protection(vma, start, end, vma->vm_page_prot, | |
334 | dirty_accountable, 0); | |
335 | ||
336 | /* | |
337 | * Private VM_LOCKED VMA becoming writable: trigger COW to avoid major | |
338 | * fault on access. | |
339 | */ | |
340 | if ((oldflags & (VM_WRITE | VM_SHARED | VM_LOCKED)) == VM_LOCKED && | |
341 | (newflags & VM_WRITE)) { | |
342 | populate_vma_page_range(vma, start, end, NULL); | |
343 | } | |
344 | ||
345 | vm_stat_account(mm, oldflags, -nrpages); | |
346 | vm_stat_account(mm, newflags, nrpages); | |
347 | perf_event_mmap(vma); | |
348 | return 0; | |
349 | ||
350 | fail: | |
351 | vm_unacct_memory(charged); | |
352 | return error; | |
353 | } | |
354 | ||
355 | SYSCALL_DEFINE3(mprotect, unsigned long, start, size_t, len, | |
356 | unsigned long, prot) | |
357 | { | |
358 | unsigned long nstart, end, tmp, reqprot; | |
359 | struct vm_area_struct *vma, *prev; | |
360 | int error = -EINVAL; | |
361 | const int grows = prot & (PROT_GROWSDOWN|PROT_GROWSUP); | |
362 | const bool rier = (current->personality & READ_IMPLIES_EXEC) && | |
363 | (prot & PROT_READ); | |
364 | ||
365 | prot &= ~(PROT_GROWSDOWN|PROT_GROWSUP); | |
366 | if (grows == (PROT_GROWSDOWN|PROT_GROWSUP)) /* can't be both */ | |
367 | return -EINVAL; | |
368 | ||
369 | if (start & ~PAGE_MASK) | |
370 | return -EINVAL; | |
371 | if (!len) | |
372 | return 0; | |
373 | len = PAGE_ALIGN(len); | |
374 | end = start + len; | |
375 | if (end <= start) | |
376 | return -ENOMEM; | |
377 | if (!arch_validate_prot(prot)) | |
378 | return -EINVAL; | |
379 | ||
380 | reqprot = prot; | |
381 | ||
382 | if (down_write_killable(¤t->mm->mmap_sem)) | |
383 | return -EINTR; | |
384 | ||
385 | vma = find_vma(current->mm, start); | |
386 | error = -ENOMEM; | |
387 | if (!vma) | |
388 | goto out; | |
389 | prev = vma->vm_prev; | |
390 | if (unlikely(grows & PROT_GROWSDOWN)) { | |
391 | if (vma->vm_start >= end) | |
392 | goto out; | |
393 | start = vma->vm_start; | |
394 | error = -EINVAL; | |
395 | if (!(vma->vm_flags & VM_GROWSDOWN)) | |
396 | goto out; | |
397 | } else { | |
398 | if (vma->vm_start > start) | |
399 | goto out; | |
400 | if (unlikely(grows & PROT_GROWSUP)) { | |
401 | end = vma->vm_end; | |
402 | error = -EINVAL; | |
403 | if (!(vma->vm_flags & VM_GROWSUP)) | |
404 | goto out; | |
405 | } | |
406 | } | |
407 | if (start > vma->vm_start) | |
408 | prev = vma; | |
409 | ||
410 | for (nstart = start ; ; ) { | |
411 | unsigned long newflags; | |
412 | int pkey = arch_override_mprotect_pkey(vma, prot, -1); | |
413 | ||
414 | /* Here we know that vma->vm_start <= nstart < vma->vm_end. */ | |
415 | ||
416 | /* Does the application expect PROT_READ to imply PROT_EXEC */ | |
417 | if (rier && (vma->vm_flags & VM_MAYEXEC)) | |
418 | prot |= PROT_EXEC; | |
419 | ||
420 | newflags = calc_vm_prot_bits(prot, pkey); | |
421 | newflags |= (vma->vm_flags & ~(VM_READ | VM_WRITE | VM_EXEC)); | |
422 | ||
423 | /* newflags >> 4 shift VM_MAY% in place of VM_% */ | |
424 | if ((newflags & ~(newflags >> 4)) & (VM_READ | VM_WRITE | VM_EXEC)) { | |
425 | error = -EACCES; | |
426 | goto out; | |
427 | } | |
428 | ||
429 | error = security_file_mprotect(vma, reqprot, prot); | |
430 | if (error) | |
431 | goto out; | |
432 | ||
433 | tmp = vma->vm_end; | |
434 | if (tmp > end) | |
435 | tmp = end; | |
436 | error = mprotect_fixup(vma, &prev, nstart, tmp, newflags); | |
437 | if (error) | |
438 | goto out; | |
439 | nstart = tmp; | |
440 | ||
441 | if (nstart < prev->vm_end) | |
442 | nstart = prev->vm_end; | |
443 | if (nstart >= end) | |
444 | goto out; | |
445 | ||
446 | vma = prev->vm_next; | |
447 | if (!vma || vma->vm_start != nstart) { | |
448 | error = -ENOMEM; | |
449 | goto out; | |
450 | } | |
451 | prot = reqprot; | |
452 | } | |
453 | out: | |
454 | up_write(¤t->mm->mmap_sem); | |
455 | return error; | |
456 | } |