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 | ||
29 | static void change_pte_range(struct mm_struct *mm, pmd_t *pmd, | |
c1e6098b PZ |
30 | unsigned long addr, unsigned long end, pgprot_t newprot, |
31 | int dirty_accountable) | |
1da177e4 | 32 | { |
0697212a | 33 | pte_t *pte, oldpte; |
705e87c0 | 34 | spinlock_t *ptl; |
1da177e4 | 35 | |
705e87c0 | 36 | pte = pte_offset_map_lock(mm, pmd, addr, &ptl); |
1da177e4 | 37 | do { |
0697212a CL |
38 | oldpte = *pte; |
39 | if (pte_present(oldpte)) { | |
1da177e4 LT |
40 | pte_t ptent; |
41 | ||
42 | /* Avoid an SMP race with hardware updated dirty/clean | |
43 | * bits by wiping the pte and then setting the new pte | |
44 | * into place. | |
45 | */ | |
c1e6098b PZ |
46 | ptent = ptep_get_and_clear(mm, addr, pte); |
47 | ptent = pte_modify(ptent, newprot); | |
48 | /* | |
49 | * Avoid taking write faults for pages we know to be | |
50 | * dirty. | |
51 | */ | |
52 | if (dirty_accountable && pte_dirty(ptent)) | |
53 | ptent = pte_mkwrite(ptent); | |
1da177e4 LT |
54 | set_pte_at(mm, addr, pte, ptent); |
55 | lazy_mmu_prot_update(ptent); | |
0697212a CL |
56 | #ifdef CONFIG_MIGRATION |
57 | } else if (!pte_file(oldpte)) { | |
58 | swp_entry_t entry = pte_to_swp_entry(oldpte); | |
59 | ||
60 | if (is_write_migration_entry(entry)) { | |
61 | /* | |
62 | * A protection check is difficult so | |
63 | * just be safe and disable write | |
64 | */ | |
65 | make_migration_entry_read(&entry); | |
66 | set_pte_at(mm, addr, pte, | |
67 | swp_entry_to_pte(entry)); | |
68 | } | |
69 | #endif | |
1da177e4 | 70 | } |
0697212a | 71 | |
1da177e4 | 72 | } while (pte++, addr += PAGE_SIZE, addr != end); |
705e87c0 | 73 | pte_unmap_unlock(pte - 1, ptl); |
1da177e4 LT |
74 | } |
75 | ||
76 | static inline void change_pmd_range(struct mm_struct *mm, pud_t *pud, | |
c1e6098b PZ |
77 | unsigned long addr, unsigned long end, pgprot_t newprot, |
78 | int dirty_accountable) | |
1da177e4 LT |
79 | { |
80 | pmd_t *pmd; | |
81 | unsigned long next; | |
82 | ||
83 | pmd = pmd_offset(pud, addr); | |
84 | do { | |
85 | next = pmd_addr_end(addr, end); | |
86 | if (pmd_none_or_clear_bad(pmd)) | |
87 | continue; | |
c1e6098b | 88 | change_pte_range(mm, pmd, addr, next, newprot, dirty_accountable); |
1da177e4 LT |
89 | } while (pmd++, addr = next, addr != end); |
90 | } | |
91 | ||
92 | static inline void change_pud_range(struct mm_struct *mm, pgd_t *pgd, | |
c1e6098b PZ |
93 | unsigned long addr, unsigned long end, pgprot_t newprot, |
94 | int dirty_accountable) | |
1da177e4 LT |
95 | { |
96 | pud_t *pud; | |
97 | unsigned long next; | |
98 | ||
99 | pud = pud_offset(pgd, addr); | |
100 | do { | |
101 | next = pud_addr_end(addr, end); | |
102 | if (pud_none_or_clear_bad(pud)) | |
103 | continue; | |
c1e6098b | 104 | change_pmd_range(mm, pud, addr, next, newprot, dirty_accountable); |
1da177e4 LT |
105 | } while (pud++, addr = next, addr != end); |
106 | } | |
107 | ||
108 | static void change_protection(struct vm_area_struct *vma, | |
c1e6098b PZ |
109 | unsigned long addr, unsigned long end, pgprot_t newprot, |
110 | int dirty_accountable) | |
1da177e4 LT |
111 | { |
112 | struct mm_struct *mm = vma->vm_mm; | |
113 | pgd_t *pgd; | |
114 | unsigned long next; | |
115 | unsigned long start = addr; | |
116 | ||
117 | BUG_ON(addr >= end); | |
118 | pgd = pgd_offset(mm, addr); | |
119 | flush_cache_range(vma, addr, end); | |
1da177e4 LT |
120 | do { |
121 | next = pgd_addr_end(addr, end); | |
122 | if (pgd_none_or_clear_bad(pgd)) | |
123 | continue; | |
c1e6098b | 124 | change_pud_range(mm, pgd, addr, next, newprot, dirty_accountable); |
1da177e4 LT |
125 | } while (pgd++, addr = next, addr != end); |
126 | flush_tlb_range(vma, start, end); | |
1da177e4 LT |
127 | } |
128 | ||
129 | static int | |
130 | mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev, | |
131 | unsigned long start, unsigned long end, unsigned long newflags) | |
132 | { | |
133 | struct mm_struct *mm = vma->vm_mm; | |
134 | unsigned long oldflags = vma->vm_flags; | |
135 | long nrpages = (end - start) >> PAGE_SHIFT; | |
136 | unsigned long charged = 0; | |
1da177e4 LT |
137 | pgoff_t pgoff; |
138 | int error; | |
c1e6098b | 139 | int dirty_accountable = 0; |
1da177e4 LT |
140 | |
141 | if (newflags == oldflags) { | |
142 | *pprev = vma; | |
143 | return 0; | |
144 | } | |
145 | ||
146 | /* | |
147 | * If we make a private mapping writable we increase our commit; | |
148 | * but (without finer accounting) cannot reduce our commit if we | |
149 | * make it unwritable again. | |
150 | * | |
151 | * FIXME? We haven't defined a VM_NORESERVE flag, so mprotecting | |
152 | * a MAP_NORESERVE private mapping to writable will now reserve. | |
153 | */ | |
154 | if (newflags & VM_WRITE) { | |
8f860591 | 155 | if (!(oldflags & (VM_ACCOUNT|VM_WRITE|VM_SHARED))) { |
1da177e4 LT |
156 | charged = nrpages; |
157 | if (security_vm_enough_memory(charged)) | |
158 | return -ENOMEM; | |
159 | newflags |= VM_ACCOUNT; | |
160 | } | |
161 | } | |
162 | ||
1da177e4 LT |
163 | /* |
164 | * First try to merge with previous and/or next vma. | |
165 | */ | |
166 | pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT); | |
167 | *pprev = vma_merge(mm, *pprev, start, end, newflags, | |
168 | vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma)); | |
169 | if (*pprev) { | |
170 | vma = *pprev; | |
171 | goto success; | |
172 | } | |
173 | ||
174 | *pprev = vma; | |
175 | ||
176 | if (start != vma->vm_start) { | |
177 | error = split_vma(mm, vma, start, 1); | |
178 | if (error) | |
179 | goto fail; | |
180 | } | |
181 | ||
182 | if (end != vma->vm_end) { | |
183 | error = split_vma(mm, vma, end, 0); | |
184 | if (error) | |
185 | goto fail; | |
186 | } | |
187 | ||
188 | success: | |
189 | /* | |
190 | * vm_flags and vm_page_prot are protected by the mmap_sem | |
191 | * held in write mode. | |
192 | */ | |
193 | vma->vm_flags = newflags; | |
d08b3851 PZ |
194 | vma->vm_page_prot = protection_map[newflags & |
195 | (VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)]; | |
c1e6098b | 196 | if (vma_wants_writenotify(vma)) { |
d08b3851 PZ |
197 | vma->vm_page_prot = protection_map[newflags & |
198 | (VM_READ|VM_WRITE|VM_EXEC)]; | |
c1e6098b PZ |
199 | dirty_accountable = 1; |
200 | } | |
d08b3851 | 201 | |
8f860591 | 202 | if (is_vm_hugetlb_page(vma)) |
d08b3851 | 203 | hugetlb_change_protection(vma, start, end, vma->vm_page_prot); |
8f860591 | 204 | else |
c1e6098b | 205 | change_protection(vma, start, end, vma->vm_page_prot, dirty_accountable); |
ab50b8ed HD |
206 | vm_stat_account(mm, oldflags, vma->vm_file, -nrpages); |
207 | vm_stat_account(mm, newflags, vma->vm_file, nrpages); | |
1da177e4 LT |
208 | return 0; |
209 | ||
210 | fail: | |
211 | vm_unacct_memory(charged); | |
212 | return error; | |
213 | } | |
214 | ||
215 | asmlinkage long | |
216 | sys_mprotect(unsigned long start, size_t len, unsigned long prot) | |
217 | { | |
218 | unsigned long vm_flags, nstart, end, tmp, reqprot; | |
219 | struct vm_area_struct *vma, *prev; | |
220 | int error = -EINVAL; | |
221 | const int grows = prot & (PROT_GROWSDOWN|PROT_GROWSUP); | |
222 | prot &= ~(PROT_GROWSDOWN|PROT_GROWSUP); | |
223 | if (grows == (PROT_GROWSDOWN|PROT_GROWSUP)) /* can't be both */ | |
224 | return -EINVAL; | |
225 | ||
226 | if (start & ~PAGE_MASK) | |
227 | return -EINVAL; | |
228 | if (!len) | |
229 | return 0; | |
230 | len = PAGE_ALIGN(len); | |
231 | end = start + len; | |
232 | if (end <= start) | |
233 | return -ENOMEM; | |
234 | if (prot & ~(PROT_READ | PROT_WRITE | PROT_EXEC | PROT_SEM)) | |
235 | return -EINVAL; | |
236 | ||
237 | reqprot = prot; | |
238 | /* | |
239 | * Does the application expect PROT_READ to imply PROT_EXEC: | |
240 | */ | |
b344e05c | 241 | if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC)) |
1da177e4 LT |
242 | prot |= PROT_EXEC; |
243 | ||
244 | vm_flags = calc_vm_prot_bits(prot); | |
245 | ||
246 | down_write(¤t->mm->mmap_sem); | |
247 | ||
248 | vma = find_vma_prev(current->mm, start, &prev); | |
249 | error = -ENOMEM; | |
250 | if (!vma) | |
251 | goto out; | |
252 | if (unlikely(grows & PROT_GROWSDOWN)) { | |
253 | if (vma->vm_start >= end) | |
254 | goto out; | |
255 | start = vma->vm_start; | |
256 | error = -EINVAL; | |
257 | if (!(vma->vm_flags & VM_GROWSDOWN)) | |
258 | goto out; | |
259 | } | |
260 | else { | |
261 | if (vma->vm_start > start) | |
262 | goto out; | |
263 | if (unlikely(grows & PROT_GROWSUP)) { | |
264 | end = vma->vm_end; | |
265 | error = -EINVAL; | |
266 | if (!(vma->vm_flags & VM_GROWSUP)) | |
267 | goto out; | |
268 | } | |
269 | } | |
270 | if (start > vma->vm_start) | |
271 | prev = vma; | |
272 | ||
273 | for (nstart = start ; ; ) { | |
274 | unsigned long newflags; | |
275 | ||
276 | /* Here we know that vma->vm_start <= nstart < vma->vm_end. */ | |
277 | ||
1da177e4 LT |
278 | newflags = vm_flags | (vma->vm_flags & ~(VM_READ | VM_WRITE | VM_EXEC)); |
279 | ||
7e2cff42 PBG |
280 | /* newflags >> 4 shift VM_MAY% in place of VM_% */ |
281 | if ((newflags & ~(newflags >> 4)) & (VM_READ | VM_WRITE | VM_EXEC)) { | |
1da177e4 LT |
282 | error = -EACCES; |
283 | goto out; | |
284 | } | |
285 | ||
286 | error = security_file_mprotect(vma, reqprot, prot); | |
287 | if (error) | |
288 | goto out; | |
289 | ||
290 | tmp = vma->vm_end; | |
291 | if (tmp > end) | |
292 | tmp = end; | |
293 | error = mprotect_fixup(vma, &prev, nstart, tmp, newflags); | |
294 | if (error) | |
295 | goto out; | |
296 | nstart = tmp; | |
297 | ||
298 | if (nstart < prev->vm_end) | |
299 | nstart = prev->vm_end; | |
300 | if (nstart >= end) | |
301 | goto out; | |
302 | ||
303 | vma = prev->vm_next; | |
304 | if (!vma || vma->vm_start != nstart) { | |
305 | error = -ENOMEM; | |
306 | goto out; | |
307 | } | |
308 | } | |
309 | out: | |
310 | up_write(¤t->mm->mmap_sem); | |
311 | return error; | |
312 | } |