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 | ||
50 | /* Avoid an SMP race with hardware updated dirty/clean | |
51 | * bits by wiping the pte and then setting the new pte | |
52 | * into place. | |
53 | */ | |
c1e6098b PZ |
54 | ptent = ptep_get_and_clear(mm, addr, pte); |
55 | ptent = pte_modify(ptent, newprot); | |
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); | |
1da177e4 | 62 | set_pte_at(mm, addr, pte, ptent); |
0697212a CL |
63 | #ifdef CONFIG_MIGRATION |
64 | } else if (!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 | #endif | |
1da177e4 | 77 | } |
0697212a | 78 | |
1da177e4 | 79 | } while (pte++, addr += PAGE_SIZE, addr != end); |
6606c3e0 | 80 | arch_leave_lazy_mmu_mode(); |
705e87c0 | 81 | pte_unmap_unlock(pte - 1, ptl); |
1da177e4 LT |
82 | } |
83 | ||
84 | static inline void change_pmd_range(struct mm_struct *mm, pud_t *pud, | |
c1e6098b PZ |
85 | unsigned long addr, unsigned long end, pgprot_t newprot, |
86 | int dirty_accountable) | |
1da177e4 LT |
87 | { |
88 | pmd_t *pmd; | |
89 | unsigned long next; | |
90 | ||
91 | pmd = pmd_offset(pud, addr); | |
92 | do { | |
93 | next = pmd_addr_end(addr, end); | |
94 | if (pmd_none_or_clear_bad(pmd)) | |
95 | continue; | |
c1e6098b | 96 | change_pte_range(mm, pmd, addr, next, newprot, dirty_accountable); |
1da177e4 LT |
97 | } while (pmd++, addr = next, addr != end); |
98 | } | |
99 | ||
100 | static inline void change_pud_range(struct mm_struct *mm, pgd_t *pgd, | |
c1e6098b PZ |
101 | unsigned long addr, unsigned long end, pgprot_t newprot, |
102 | int dirty_accountable) | |
1da177e4 LT |
103 | { |
104 | pud_t *pud; | |
105 | unsigned long next; | |
106 | ||
107 | pud = pud_offset(pgd, addr); | |
108 | do { | |
109 | next = pud_addr_end(addr, end); | |
110 | if (pud_none_or_clear_bad(pud)) | |
111 | continue; | |
c1e6098b | 112 | change_pmd_range(mm, pud, addr, next, newprot, dirty_accountable); |
1da177e4 LT |
113 | } while (pud++, addr = next, addr != end); |
114 | } | |
115 | ||
116 | static void change_protection(struct vm_area_struct *vma, | |
c1e6098b PZ |
117 | unsigned long addr, unsigned long end, pgprot_t newprot, |
118 | int dirty_accountable) | |
1da177e4 LT |
119 | { |
120 | struct mm_struct *mm = vma->vm_mm; | |
121 | pgd_t *pgd; | |
122 | unsigned long next; | |
123 | unsigned long start = addr; | |
124 | ||
125 | BUG_ON(addr >= end); | |
126 | pgd = pgd_offset(mm, addr); | |
127 | flush_cache_range(vma, addr, end); | |
1da177e4 LT |
128 | do { |
129 | next = pgd_addr_end(addr, end); | |
130 | if (pgd_none_or_clear_bad(pgd)) | |
131 | continue; | |
c1e6098b | 132 | change_pud_range(mm, pgd, addr, next, newprot, dirty_accountable); |
1da177e4 LT |
133 | } while (pgd++, addr = next, addr != end); |
134 | flush_tlb_range(vma, start, end); | |
1da177e4 LT |
135 | } |
136 | ||
b6a2fea3 | 137 | int |
1da177e4 LT |
138 | mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev, |
139 | unsigned long start, unsigned long end, unsigned long newflags) | |
140 | { | |
141 | struct mm_struct *mm = vma->vm_mm; | |
142 | unsigned long oldflags = vma->vm_flags; | |
143 | long nrpages = (end - start) >> PAGE_SHIFT; | |
144 | unsigned long charged = 0; | |
1da177e4 LT |
145 | pgoff_t pgoff; |
146 | int error; | |
c1e6098b | 147 | int dirty_accountable = 0; |
1da177e4 LT |
148 | |
149 | if (newflags == oldflags) { | |
150 | *pprev = vma; | |
151 | return 0; | |
152 | } | |
153 | ||
154 | /* | |
155 | * If we make a private mapping writable we increase our commit; | |
156 | * but (without finer accounting) cannot reduce our commit if we | |
157 | * make it unwritable again. | |
158 | * | |
159 | * FIXME? We haven't defined a VM_NORESERVE flag, so mprotecting | |
160 | * a MAP_NORESERVE private mapping to writable will now reserve. | |
161 | */ | |
162 | if (newflags & VM_WRITE) { | |
8f860591 | 163 | if (!(oldflags & (VM_ACCOUNT|VM_WRITE|VM_SHARED))) { |
1da177e4 LT |
164 | charged = nrpages; |
165 | if (security_vm_enough_memory(charged)) | |
166 | return -ENOMEM; | |
167 | newflags |= VM_ACCOUNT; | |
168 | } | |
169 | } | |
170 | ||
1da177e4 LT |
171 | /* |
172 | * First try to merge with previous and/or next vma. | |
173 | */ | |
174 | pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT); | |
175 | *pprev = vma_merge(mm, *pprev, start, end, newflags, | |
176 | vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma)); | |
177 | if (*pprev) { | |
178 | vma = *pprev; | |
179 | goto success; | |
180 | } | |
181 | ||
182 | *pprev = vma; | |
183 | ||
184 | if (start != vma->vm_start) { | |
185 | error = split_vma(mm, vma, start, 1); | |
186 | if (error) | |
187 | goto fail; | |
188 | } | |
189 | ||
190 | if (end != vma->vm_end) { | |
191 | error = split_vma(mm, vma, end, 0); | |
192 | if (error) | |
193 | goto fail; | |
194 | } | |
195 | ||
196 | success: | |
197 | /* | |
198 | * vm_flags and vm_page_prot are protected by the mmap_sem | |
199 | * held in write mode. | |
200 | */ | |
201 | vma->vm_flags = newflags; | |
1c12c4cf VP |
202 | vma->vm_page_prot = pgprot_modify(vma->vm_page_prot, |
203 | vm_get_page_prot(newflags)); | |
204 | ||
c1e6098b | 205 | if (vma_wants_writenotify(vma)) { |
1ddd439e | 206 | vma->vm_page_prot = vm_get_page_prot(newflags & ~VM_SHARED); |
c1e6098b PZ |
207 | dirty_accountable = 1; |
208 | } | |
d08b3851 | 209 | |
8f860591 | 210 | if (is_vm_hugetlb_page(vma)) |
d08b3851 | 211 | hugetlb_change_protection(vma, start, end, vma->vm_page_prot); |
8f860591 | 212 | else |
c1e6098b | 213 | change_protection(vma, start, end, vma->vm_page_prot, dirty_accountable); |
ab50b8ed HD |
214 | vm_stat_account(mm, oldflags, vma->vm_file, -nrpages); |
215 | vm_stat_account(mm, newflags, vma->vm_file, nrpages); | |
1da177e4 LT |
216 | return 0; |
217 | ||
218 | fail: | |
219 | vm_unacct_memory(charged); | |
220 | return error; | |
221 | } | |
222 | ||
223 | asmlinkage long | |
224 | sys_mprotect(unsigned long start, size_t len, unsigned long prot) | |
225 | { | |
226 | unsigned long vm_flags, nstart, end, tmp, reqprot; | |
227 | struct vm_area_struct *vma, *prev; | |
228 | int error = -EINVAL; | |
229 | const int grows = prot & (PROT_GROWSDOWN|PROT_GROWSUP); | |
230 | prot &= ~(PROT_GROWSDOWN|PROT_GROWSUP); | |
231 | if (grows == (PROT_GROWSDOWN|PROT_GROWSUP)) /* can't be both */ | |
232 | return -EINVAL; | |
233 | ||
234 | if (start & ~PAGE_MASK) | |
235 | return -EINVAL; | |
236 | if (!len) | |
237 | return 0; | |
238 | len = PAGE_ALIGN(len); | |
239 | end = start + len; | |
240 | if (end <= start) | |
241 | return -ENOMEM; | |
242 | if (prot & ~(PROT_READ | PROT_WRITE | PROT_EXEC | PROT_SEM)) | |
243 | return -EINVAL; | |
244 | ||
245 | reqprot = prot; | |
246 | /* | |
247 | * Does the application expect PROT_READ to imply PROT_EXEC: | |
248 | */ | |
b344e05c | 249 | if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC)) |
1da177e4 LT |
250 | prot |= PROT_EXEC; |
251 | ||
252 | vm_flags = calc_vm_prot_bits(prot); | |
253 | ||
254 | down_write(¤t->mm->mmap_sem); | |
255 | ||
256 | vma = find_vma_prev(current->mm, start, &prev); | |
257 | error = -ENOMEM; | |
258 | if (!vma) | |
259 | goto out; | |
260 | if (unlikely(grows & PROT_GROWSDOWN)) { | |
261 | if (vma->vm_start >= end) | |
262 | goto out; | |
263 | start = vma->vm_start; | |
264 | error = -EINVAL; | |
265 | if (!(vma->vm_flags & VM_GROWSDOWN)) | |
266 | goto out; | |
267 | } | |
268 | else { | |
269 | if (vma->vm_start > start) | |
270 | goto out; | |
271 | if (unlikely(grows & PROT_GROWSUP)) { | |
272 | end = vma->vm_end; | |
273 | error = -EINVAL; | |
274 | if (!(vma->vm_flags & VM_GROWSUP)) | |
275 | goto out; | |
276 | } | |
277 | } | |
278 | if (start > vma->vm_start) | |
279 | prev = vma; | |
280 | ||
281 | for (nstart = start ; ; ) { | |
282 | unsigned long newflags; | |
283 | ||
284 | /* Here we know that vma->vm_start <= nstart < vma->vm_end. */ | |
285 | ||
1da177e4 LT |
286 | newflags = vm_flags | (vma->vm_flags & ~(VM_READ | VM_WRITE | VM_EXEC)); |
287 | ||
7e2cff42 PBG |
288 | /* newflags >> 4 shift VM_MAY% in place of VM_% */ |
289 | if ((newflags & ~(newflags >> 4)) & (VM_READ | VM_WRITE | VM_EXEC)) { | |
1da177e4 LT |
290 | error = -EACCES; |
291 | goto out; | |
292 | } | |
293 | ||
294 | error = security_file_mprotect(vma, reqprot, prot); | |
295 | if (error) | |
296 | goto out; | |
297 | ||
298 | tmp = vma->vm_end; | |
299 | if (tmp > end) | |
300 | tmp = end; | |
301 | error = mprotect_fixup(vma, &prev, nstart, tmp, newflags); | |
302 | if (error) | |
303 | goto out; | |
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 | } |