Commit | Line | Data |
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1da177e4 LT |
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@redhat.com> | |
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> | |
0697212a CL |
22 | #include <linux/swap.h> |
23 | #include <linux/swapops.h> | |
1da177e4 LT |
24 | #include <asm/uaccess.h> |
25 | #include <asm/pgtable.h> | |
26 | #include <asm/cacheflush.h> | |
27 | #include <asm/tlbflush.h> | |
28 | ||
1c12c4cf VP |
29 | #ifndef pgprot_modify |
30 | static inline pgprot_t pgprot_modify(pgprot_t oldprot, pgprot_t newprot) | |
31 | { | |
32 | return newprot; | |
33 | } | |
34 | #endif | |
35 | ||
1da177e4 | 36 | static void change_pte_range(struct mm_struct *mm, pmd_t *pmd, |
c1e6098b PZ |
37 | unsigned long addr, unsigned long end, pgprot_t newprot, |
38 | int dirty_accountable) | |
1da177e4 | 39 | { |
0697212a | 40 | pte_t *pte, oldpte; |
705e87c0 | 41 | spinlock_t *ptl; |
1da177e4 | 42 | |
705e87c0 | 43 | pte = pte_offset_map_lock(mm, pmd, addr, &ptl); |
6606c3e0 | 44 | arch_enter_lazy_mmu_mode(); |
1da177e4 | 45 | do { |
0697212a CL |
46 | oldpte = *pte; |
47 | if (pte_present(oldpte)) { | |
1da177e4 LT |
48 | pte_t ptent; |
49 | ||
1ea0704e | 50 | ptent = ptep_modify_prot_start(mm, addr, pte); |
c1e6098b | 51 | ptent = pte_modify(ptent, newprot); |
1ea0704e | 52 | |
c1e6098b PZ |
53 | /* |
54 | * Avoid taking write faults for pages we know to be | |
55 | * dirty. | |
56 | */ | |
57 | if (dirty_accountable && pte_dirty(ptent)) | |
58 | ptent = pte_mkwrite(ptent); | |
1ea0704e JF |
59 | |
60 | ptep_modify_prot_commit(mm, addr, pte, ptent); | |
0697212a CL |
61 | #ifdef CONFIG_MIGRATION |
62 | } else if (!pte_file(oldpte)) { | |
63 | swp_entry_t entry = pte_to_swp_entry(oldpte); | |
64 | ||
65 | if (is_write_migration_entry(entry)) { | |
66 | /* | |
67 | * A protection check is difficult so | |
68 | * just be safe and disable write | |
69 | */ | |
70 | make_migration_entry_read(&entry); | |
71 | set_pte_at(mm, addr, pte, | |
72 | swp_entry_to_pte(entry)); | |
73 | } | |
74 | #endif | |
1da177e4 | 75 | } |
0697212a | 76 | |
1da177e4 | 77 | } while (pte++, addr += PAGE_SIZE, addr != end); |
6606c3e0 | 78 | arch_leave_lazy_mmu_mode(); |
705e87c0 | 79 | pte_unmap_unlock(pte - 1, ptl); |
1da177e4 LT |
80 | } |
81 | ||
82 | static inline void change_pmd_range(struct mm_struct *mm, pud_t *pud, | |
c1e6098b PZ |
83 | unsigned long addr, unsigned long end, pgprot_t newprot, |
84 | int dirty_accountable) | |
1da177e4 LT |
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; | |
c1e6098b | 94 | change_pte_range(mm, pmd, addr, next, newprot, dirty_accountable); |
1da177e4 LT |
95 | } while (pmd++, addr = next, addr != end); |
96 | } | |
97 | ||
98 | static inline void change_pud_range(struct mm_struct *mm, pgd_t *pgd, | |
c1e6098b PZ |
99 | unsigned long addr, unsigned long end, pgprot_t newprot, |
100 | int dirty_accountable) | |
1da177e4 LT |
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; | |
c1e6098b | 110 | change_pmd_range(mm, pud, addr, next, newprot, dirty_accountable); |
1da177e4 LT |
111 | } while (pud++, addr = next, addr != end); |
112 | } | |
113 | ||
114 | static void change_protection(struct vm_area_struct *vma, | |
c1e6098b PZ |
115 | unsigned long addr, unsigned long end, pgprot_t newprot, |
116 | int dirty_accountable) | |
1da177e4 LT |
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); | |
1da177e4 LT |
126 | do { |
127 | next = pgd_addr_end(addr, end); | |
128 | if (pgd_none_or_clear_bad(pgd)) | |
129 | continue; | |
c1e6098b | 130 | change_pud_range(mm, pgd, addr, next, newprot, dirty_accountable); |
1da177e4 LT |
131 | } while (pgd++, addr = next, addr != end); |
132 | flush_tlb_range(vma, start, end); | |
1da177e4 LT |
133 | } |
134 | ||
b6a2fea3 | 135 | int |
1da177e4 LT |
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; | |
1da177e4 LT |
143 | pgoff_t pgoff; |
144 | int error; | |
c1e6098b | 145 | int dirty_accountable = 0; |
1da177e4 LT |
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. | |
1da177e4 LT |
156 | */ |
157 | if (newflags & VM_WRITE) { | |
cdfd4325 AW |
158 | if (!(oldflags & (VM_ACCOUNT|VM_WRITE| |
159 | VM_SHARED|VM_NORESERVE))) { | |
1da177e4 LT |
160 | charged = nrpages; |
161 | if (security_vm_enough_memory(charged)) | |
162 | return -ENOMEM; | |
163 | newflags |= VM_ACCOUNT; | |
164 | } | |
165 | } | |
166 | ||
1da177e4 LT |
167 | /* |
168 | * First try to merge with previous and/or next vma. | |
169 | */ | |
170 | pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT); | |
171 | *pprev = vma_merge(mm, *pprev, start, end, newflags, | |
172 | vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma)); | |
173 | if (*pprev) { | |
174 | vma = *pprev; | |
175 | goto success; | |
176 | } | |
177 | ||
178 | *pprev = vma; | |
179 | ||
180 | if (start != vma->vm_start) { | |
181 | error = split_vma(mm, vma, start, 1); | |
182 | if (error) | |
183 | goto fail; | |
184 | } | |
185 | ||
186 | if (end != vma->vm_end) { | |
187 | error = split_vma(mm, vma, end, 0); | |
188 | if (error) | |
189 | goto fail; | |
190 | } | |
191 | ||
192 | success: | |
193 | /* | |
194 | * vm_flags and vm_page_prot are protected by the mmap_sem | |
195 | * held in write mode. | |
196 | */ | |
197 | vma->vm_flags = newflags; | |
1c12c4cf VP |
198 | vma->vm_page_prot = pgprot_modify(vma->vm_page_prot, |
199 | vm_get_page_prot(newflags)); | |
200 | ||
c1e6098b | 201 | if (vma_wants_writenotify(vma)) { |
1ddd439e | 202 | vma->vm_page_prot = vm_get_page_prot(newflags & ~VM_SHARED); |
c1e6098b PZ |
203 | dirty_accountable = 1; |
204 | } | |
d08b3851 | 205 | |
8f860591 | 206 | if (is_vm_hugetlb_page(vma)) |
d08b3851 | 207 | hugetlb_change_protection(vma, start, end, vma->vm_page_prot); |
8f860591 | 208 | else |
c1e6098b | 209 | change_protection(vma, start, end, vma->vm_page_prot, dirty_accountable); |
ab50b8ed HD |
210 | vm_stat_account(mm, oldflags, vma->vm_file, -nrpages); |
211 | vm_stat_account(mm, newflags, vma->vm_file, nrpages); | |
1da177e4 LT |
212 | return 0; |
213 | ||
214 | fail: | |
215 | vm_unacct_memory(charged); | |
216 | return error; | |
217 | } | |
218 | ||
219 | asmlinkage long | |
220 | sys_mprotect(unsigned long start, size_t len, unsigned long prot) | |
221 | { | |
222 | unsigned long vm_flags, nstart, end, tmp, reqprot; | |
223 | struct vm_area_struct *vma, *prev; | |
224 | int error = -EINVAL; | |
225 | const int grows = prot & (PROT_GROWSDOWN|PROT_GROWSUP); | |
226 | prot &= ~(PROT_GROWSDOWN|PROT_GROWSUP); | |
227 | if (grows == (PROT_GROWSDOWN|PROT_GROWSUP)) /* can't be both */ | |
228 | return -EINVAL; | |
229 | ||
230 | if (start & ~PAGE_MASK) | |
231 | return -EINVAL; | |
232 | if (!len) | |
233 | return 0; | |
234 | len = PAGE_ALIGN(len); | |
235 | end = start + len; | |
236 | if (end <= start) | |
237 | return -ENOMEM; | |
b845f313 | 238 | if (!arch_validate_prot(prot)) |
1da177e4 LT |
239 | return -EINVAL; |
240 | ||
241 | reqprot = prot; | |
242 | /* | |
243 | * Does the application expect PROT_READ to imply PROT_EXEC: | |
244 | */ | |
b344e05c | 245 | if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC)) |
1da177e4 LT |
246 | prot |= PROT_EXEC; |
247 | ||
248 | vm_flags = calc_vm_prot_bits(prot); | |
249 | ||
250 | down_write(¤t->mm->mmap_sem); | |
251 | ||
252 | vma = find_vma_prev(current->mm, start, &prev); | |
253 | error = -ENOMEM; | |
254 | if (!vma) | |
255 | goto out; | |
256 | if (unlikely(grows & PROT_GROWSDOWN)) { | |
257 | if (vma->vm_start >= end) | |
258 | goto out; | |
259 | start = vma->vm_start; | |
260 | error = -EINVAL; | |
261 | if (!(vma->vm_flags & VM_GROWSDOWN)) | |
262 | goto out; | |
263 | } | |
264 | else { | |
265 | if (vma->vm_start > start) | |
266 | goto out; | |
267 | if (unlikely(grows & PROT_GROWSUP)) { | |
268 | end = vma->vm_end; | |
269 | error = -EINVAL; | |
270 | if (!(vma->vm_flags & VM_GROWSUP)) | |
271 | goto out; | |
272 | } | |
273 | } | |
274 | if (start > vma->vm_start) | |
275 | prev = vma; | |
276 | ||
277 | for (nstart = start ; ; ) { | |
278 | unsigned long newflags; | |
279 | ||
280 | /* Here we know that vma->vm_start <= nstart < vma->vm_end. */ | |
281 | ||
1da177e4 LT |
282 | newflags = vm_flags | (vma->vm_flags & ~(VM_READ | VM_WRITE | VM_EXEC)); |
283 | ||
7e2cff42 PBG |
284 | /* newflags >> 4 shift VM_MAY% in place of VM_% */ |
285 | if ((newflags & ~(newflags >> 4)) & (VM_READ | VM_WRITE | VM_EXEC)) { | |
1da177e4 LT |
286 | error = -EACCES; |
287 | goto out; | |
288 | } | |
289 | ||
290 | error = security_file_mprotect(vma, reqprot, prot); | |
291 | if (error) | |
292 | goto out; | |
293 | ||
294 | tmp = vma->vm_end; | |
295 | if (tmp > end) | |
296 | tmp = end; | |
297 | error = mprotect_fixup(vma, &prev, nstart, tmp, newflags); | |
298 | if (error) | |
299 | goto out; | |
300 | nstart = tmp; | |
301 | ||
302 | if (nstart < prev->vm_end) | |
303 | nstart = prev->vm_end; | |
304 | if (nstart >= end) | |
305 | goto out; | |
306 | ||
307 | vma = prev->vm_next; | |
308 | if (!vma || vma->vm_start != nstart) { | |
309 | error = -ENOMEM; | |
310 | goto out; | |
311 | } | |
312 | } | |
313 | out: | |
314 | up_write(¤t->mm->mmap_sem); | |
315 | return error; | |
316 | } |