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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/slab.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 <asm/uaccess.h> |
28 | #include <asm/pgtable.h> |
29 | #include <asm/cacheflush.h> |
30 | #include <asm/tlbflush.h> |
31 | |
32 | #ifndef pgprot_modify |
33 | static inline pgprot_t pgprot_modify(pgprot_t oldprot, pgprot_t newprot) |
34 | { |
35 | return newprot; |
36 | } |
37 | #endif |
38 | |
39 | static void change_pte_range(struct mm_struct *mm, pmd_t *pmd, |
40 | unsigned long addr, unsigned long end, pgprot_t newprot, |
41 | int dirty_accountable) |
42 | { |
43 | pte_t *pte, oldpte; |
44 | spinlock_t *ptl; |
45 | |
46 | pte = pte_offset_map_lock(mm, pmd, addr, &ptl); |
47 | arch_enter_lazy_mmu_mode(); |
48 | do { |
49 | oldpte = *pte; |
50 | if (pte_present(oldpte)) { |
51 | pte_t ptent; |
52 | |
53 | ptent = ptep_modify_prot_start(mm, addr, pte); |
54 | ptent = pte_modify(ptent, newprot); |
55 | |
56 | /* |
57 | * Avoid taking write faults for pages we know to be |
58 | * dirty. |
59 | */ |
60 | if (dirty_accountable && pte_dirty(ptent)) |
61 | ptent = pte_mkwrite(ptent); |
62 | |
63 | ptep_modify_prot_commit(mm, addr, pte, ptent); |
64 | } else if (PAGE_MIGRATION && !pte_file(oldpte)) { |
65 | swp_entry_t entry = pte_to_swp_entry(oldpte); |
66 | |
67 | if (is_write_migration_entry(entry)) { |
68 | /* |
69 | * A protection check is difficult so |
70 | * just be safe and disable write |
71 | */ |
72 | make_migration_entry_read(&entry); |
73 | set_pte_at(mm, addr, pte, |
74 | swp_entry_to_pte(entry)); |
75 | } |
76 | } |
77 | } while (pte++, addr += PAGE_SIZE, addr != end); |
78 | arch_leave_lazy_mmu_mode(); |
79 | pte_unmap_unlock(pte - 1, ptl); |
80 | } |
81 | |
82 | static inline void change_pmd_range(struct mm_struct *mm, pud_t *pud, |
83 | unsigned long addr, unsigned long end, pgprot_t newprot, |
84 | int dirty_accountable) |
85 | { |
86 | pmd_t *pmd; |
87 | unsigned long next; |
88 | |
89 | pmd = pmd_offset(pud, addr); |
90 | do { |
91 | next = pmd_addr_end(addr, end); |
92 | if (pmd_none_or_clear_bad(pmd)) |
93 | continue; |
94 | change_pte_range(mm, pmd, addr, next, newprot, dirty_accountable); |
95 | } while (pmd++, addr = next, addr != end); |
96 | } |
97 | |
98 | static inline void change_pud_range(struct mm_struct *mm, pgd_t *pgd, |
99 | unsigned long addr, unsigned long end, pgprot_t newprot, |
100 | int dirty_accountable) |
101 | { |
102 | pud_t *pud; |
103 | unsigned long next; |
104 | |
105 | pud = pud_offset(pgd, addr); |
106 | do { |
107 | next = pud_addr_end(addr, end); |
108 | if (pud_none_or_clear_bad(pud)) |
109 | continue; |
110 | change_pmd_range(mm, pud, addr, next, newprot, dirty_accountable); |
111 | } while (pud++, addr = next, addr != end); |
112 | } |
113 | |
114 | static void change_protection(struct vm_area_struct *vma, |
115 | unsigned long addr, unsigned long end, pgprot_t newprot, |
116 | int dirty_accountable) |
117 | { |
118 | struct mm_struct *mm = vma->vm_mm; |
119 | pgd_t *pgd; |
120 | unsigned long next; |
121 | unsigned long start = addr; |
122 | |
123 | BUG_ON(addr >= end); |
124 | pgd = pgd_offset(mm, addr); |
125 | flush_cache_range(vma, addr, end); |
126 | do { |
127 | next = pgd_addr_end(addr, end); |
128 | if (pgd_none_or_clear_bad(pgd)) |
129 | continue; |
130 | change_pud_range(mm, pgd, addr, next, newprot, dirty_accountable); |
131 | } while (pgd++, addr = next, addr != end); |
132 | flush_tlb_range(vma, start, end); |
133 | } |
134 | |
135 | int |
136 | mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev, |
137 | unsigned long start, unsigned long end, unsigned long newflags) |
138 | { |
139 | struct mm_struct *mm = vma->vm_mm; |
140 | unsigned long oldflags = vma->vm_flags; |
141 | long nrpages = (end - start) >> PAGE_SHIFT; |
142 | unsigned long charged = 0; |
143 | pgoff_t pgoff; |
144 | int error; |
145 | int dirty_accountable = 0; |
146 | |
147 | if (newflags == oldflags) { |
148 | *pprev = vma; |
149 | return 0; |
150 | } |
151 | |
152 | /* |
153 | * If we make a private mapping writable we increase our commit; |
154 | * but (without finer accounting) cannot reduce our commit if we |
155 | * make it unwritable again. hugetlb mapping were accounted for |
156 | * even if read-only so there is no need to account for them here |
157 | */ |
158 | if (newflags & VM_WRITE) { |
159 | if (!(oldflags & (VM_ACCOUNT|VM_WRITE|VM_HUGETLB| |
160 | VM_SHARED|VM_NORESERVE))) { |
161 | charged = nrpages; |
162 | if (security_vm_enough_memory(charged)) |
163 | return -ENOMEM; |
164 | newflags |= VM_ACCOUNT; |
165 | } |
166 | } |
167 | |
168 | /* |
169 | * First try to merge with previous and/or next vma. |
170 | */ |
171 | pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT); |
172 | *pprev = vma_merge(mm, *pprev, start, end, newflags, |
173 | vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma)); |
174 | if (*pprev) { |
175 | vma = *pprev; |
176 | goto success; |
177 | } |
178 | |
179 | *pprev = vma; |
180 | |
181 | if (start != vma->vm_start) { |
182 | error = split_vma(mm, vma, start, 1); |
183 | if (error) |
184 | goto fail; |
185 | } |
186 | |
187 | if (end != vma->vm_end) { |
188 | error = split_vma(mm, vma, end, 0); |
189 | if (error) |
190 | goto fail; |
191 | } |
192 | |
193 | success: |
194 | /* |
195 | * vm_flags and vm_page_prot are protected by the mmap_sem |
196 | * held in write mode. |
197 | */ |
198 | vma->vm_flags = newflags; |
199 | vma->vm_page_prot = pgprot_modify(vma->vm_page_prot, |
200 | vm_get_page_prot(newflags)); |
201 | |
202 | if (vma_wants_writenotify(vma)) { |
203 | vma->vm_page_prot = vm_get_page_prot(newflags & ~VM_SHARED); |
204 | dirty_accountable = 1; |
205 | } |
206 | |
207 | mmu_notifier_invalidate_range_start(mm, start, end); |
208 | if (is_vm_hugetlb_page(vma)) |
209 | hugetlb_change_protection(vma, start, end, vma->vm_page_prot); |
210 | else |
211 | change_protection(vma, start, end, vma->vm_page_prot, dirty_accountable); |
212 | mmu_notifier_invalidate_range_end(mm, start, end); |
213 | vm_stat_account(mm, oldflags, vma->vm_file, -nrpages); |
214 | vm_stat_account(mm, newflags, vma->vm_file, nrpages); |
215 | return 0; |
216 | |
217 | fail: |
218 | vm_unacct_memory(charged); |
219 | return error; |
220 | } |
221 | |
222 | SYSCALL_DEFINE3(mprotect, unsigned long, start, size_t, len, |
223 | unsigned long, prot) |
224 | { |
225 | unsigned long vm_flags, nstart, end, tmp, reqprot; |
226 | struct vm_area_struct *vma, *prev; |
227 | int error = -EINVAL; |
228 | const int grows = prot & (PROT_GROWSDOWN|PROT_GROWSUP); |
229 | prot &= ~(PROT_GROWSDOWN|PROT_GROWSUP); |
230 | if (grows == (PROT_GROWSDOWN|PROT_GROWSUP)) /* can't be both */ |
231 | return -EINVAL; |
232 | |
233 | if (start & ~PAGE_MASK) |
234 | return -EINVAL; |
235 | if (!len) |
236 | return 0; |
237 | len = PAGE_ALIGN(len); |
238 | end = start + len; |
239 | if (end <= start) |
240 | return -ENOMEM; |
241 | if (!arch_validate_prot(prot)) |
242 | return -EINVAL; |
243 | |
244 | reqprot = prot; |
245 | /* |
246 | * Does the application expect PROT_READ to imply PROT_EXEC: |
247 | */ |
248 | if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC)) |
249 | prot |= PROT_EXEC; |
250 | |
251 | vm_flags = calc_vm_prot_bits(prot); |
252 | |
253 | down_write(¤t->mm->mmap_sem); |
254 | |
255 | vma = find_vma_prev(current->mm, start, &prev); |
256 | error = -ENOMEM; |
257 | if (!vma) |
258 | goto out; |
259 | if (unlikely(grows & PROT_GROWSDOWN)) { |
260 | if (vma->vm_start >= end) |
261 | goto out; |
262 | start = vma->vm_start; |
263 | error = -EINVAL; |
264 | if (!(vma->vm_flags & VM_GROWSDOWN)) |
265 | goto out; |
266 | } |
267 | else { |
268 | if (vma->vm_start > start) |
269 | goto out; |
270 | if (unlikely(grows & PROT_GROWSUP)) { |
271 | end = vma->vm_end; |
272 | error = -EINVAL; |
273 | if (!(vma->vm_flags & VM_GROWSUP)) |
274 | goto out; |
275 | } |
276 | } |
277 | if (start > vma->vm_start) |
278 | prev = vma; |
279 | |
280 | for (nstart = start ; ; ) { |
281 | unsigned long newflags; |
282 | |
283 | /* Here we know that vma->vm_start <= nstart < vma->vm_end. */ |
284 | |
285 | newflags = vm_flags | (vma->vm_flags & ~(VM_READ | VM_WRITE | VM_EXEC)); |
286 | |
287 | /* newflags >> 4 shift VM_MAY% in place of VM_% */ |
288 | if ((newflags & ~(newflags >> 4)) & (VM_READ | VM_WRITE | VM_EXEC)) { |
289 | error = -EACCES; |
290 | goto out; |
291 | } |
292 | |
293 | error = security_file_mprotect(vma, reqprot, prot); |
294 | if (error) |
295 | goto out; |
296 | |
297 | tmp = vma->vm_end; |
298 | if (tmp > end) |
299 | tmp = end; |
300 | error = mprotect_fixup(vma, &prev, nstart, tmp, newflags); |
301 | if (error) |
302 | goto out; |
303 | perf_event_mmap(vma); |
304 | nstart = tmp; |
305 | |
306 | if (nstart < prev->vm_end) |
307 | nstart = prev->vm_end; |
308 | if (nstart >= end) |
309 | goto out; |
310 | |
311 | vma = prev->vm_next; |
312 | if (!vma || vma->vm_start != nstart) { |
313 | error = -ENOMEM; |
314 | goto out; |
315 | } |
316 | } |
317 | out: |
318 | up_write(¤t->mm->mmap_sem); |
319 | return error; |
320 | } |
321 |
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