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> | |
22 | ||
23 | #include <asm/uaccess.h> | |
24 | #include <asm/pgtable.h> | |
25 | #include <asm/cacheflush.h> | |
26 | #include <asm/tlbflush.h> | |
27 | ||
28 | static void change_pte_range(struct mm_struct *mm, pmd_t *pmd, | |
29 | unsigned long addr, unsigned long end, pgprot_t newprot) | |
30 | { | |
31 | pte_t *pte; | |
705e87c0 | 32 | spinlock_t *ptl; |
1da177e4 | 33 | |
705e87c0 | 34 | pte = pte_offset_map_lock(mm, pmd, addr, &ptl); |
1da177e4 LT |
35 | do { |
36 | if (pte_present(*pte)) { | |
37 | pte_t ptent; | |
38 | ||
39 | /* Avoid an SMP race with hardware updated dirty/clean | |
40 | * bits by wiping the pte and then setting the new pte | |
41 | * into place. | |
42 | */ | |
43 | ptent = pte_modify(ptep_get_and_clear(mm, addr, pte), newprot); | |
44 | set_pte_at(mm, addr, pte, ptent); | |
45 | lazy_mmu_prot_update(ptent); | |
46 | } | |
47 | } while (pte++, addr += PAGE_SIZE, addr != end); | |
705e87c0 | 48 | pte_unmap_unlock(pte - 1, ptl); |
1da177e4 LT |
49 | } |
50 | ||
51 | static inline void change_pmd_range(struct mm_struct *mm, pud_t *pud, | |
52 | unsigned long addr, unsigned long end, pgprot_t newprot) | |
53 | { | |
54 | pmd_t *pmd; | |
55 | unsigned long next; | |
56 | ||
57 | pmd = pmd_offset(pud, addr); | |
58 | do { | |
59 | next = pmd_addr_end(addr, end); | |
60 | if (pmd_none_or_clear_bad(pmd)) | |
61 | continue; | |
62 | change_pte_range(mm, pmd, addr, next, newprot); | |
63 | } while (pmd++, addr = next, addr != end); | |
64 | } | |
65 | ||
66 | static inline void change_pud_range(struct mm_struct *mm, pgd_t *pgd, | |
67 | unsigned long addr, unsigned long end, pgprot_t newprot) | |
68 | { | |
69 | pud_t *pud; | |
70 | unsigned long next; | |
71 | ||
72 | pud = pud_offset(pgd, addr); | |
73 | do { | |
74 | next = pud_addr_end(addr, end); | |
75 | if (pud_none_or_clear_bad(pud)) | |
76 | continue; | |
77 | change_pmd_range(mm, pud, addr, next, newprot); | |
78 | } while (pud++, addr = next, addr != end); | |
79 | } | |
80 | ||
81 | static void change_protection(struct vm_area_struct *vma, | |
82 | unsigned long addr, unsigned long end, pgprot_t newprot) | |
83 | { | |
84 | struct mm_struct *mm = vma->vm_mm; | |
85 | pgd_t *pgd; | |
86 | unsigned long next; | |
87 | unsigned long start = addr; | |
88 | ||
89 | BUG_ON(addr >= end); | |
90 | pgd = pgd_offset(mm, addr); | |
91 | flush_cache_range(vma, addr, end); | |
1da177e4 LT |
92 | do { |
93 | next = pgd_addr_end(addr, end); | |
94 | if (pgd_none_or_clear_bad(pgd)) | |
95 | continue; | |
96 | change_pud_range(mm, pgd, addr, next, newprot); | |
97 | } while (pgd++, addr = next, addr != end); | |
98 | flush_tlb_range(vma, start, end); | |
1da177e4 LT |
99 | } |
100 | ||
101 | static int | |
102 | mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev, | |
103 | unsigned long start, unsigned long end, unsigned long newflags) | |
104 | { | |
105 | struct mm_struct *mm = vma->vm_mm; | |
106 | unsigned long oldflags = vma->vm_flags; | |
107 | long nrpages = (end - start) >> PAGE_SHIFT; | |
108 | unsigned long charged = 0; | |
109 | pgprot_t newprot; | |
110 | pgoff_t pgoff; | |
111 | int error; | |
112 | ||
113 | if (newflags == oldflags) { | |
114 | *pprev = vma; | |
115 | return 0; | |
116 | } | |
117 | ||
118 | /* | |
119 | * If we make a private mapping writable we increase our commit; | |
120 | * but (without finer accounting) cannot reduce our commit if we | |
121 | * make it unwritable again. | |
122 | * | |
123 | * FIXME? We haven't defined a VM_NORESERVE flag, so mprotecting | |
124 | * a MAP_NORESERVE private mapping to writable will now reserve. | |
125 | */ | |
126 | if (newflags & VM_WRITE) { | |
127 | if (!(oldflags & (VM_ACCOUNT|VM_WRITE|VM_SHARED|VM_HUGETLB))) { | |
128 | charged = nrpages; | |
129 | if (security_vm_enough_memory(charged)) | |
130 | return -ENOMEM; | |
131 | newflags |= VM_ACCOUNT; | |
132 | } | |
133 | } | |
134 | ||
135 | newprot = protection_map[newflags & 0xf]; | |
136 | ||
137 | /* | |
138 | * First try to merge with previous and/or next vma. | |
139 | */ | |
140 | pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT); | |
141 | *pprev = vma_merge(mm, *pprev, start, end, newflags, | |
142 | vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma)); | |
143 | if (*pprev) { | |
144 | vma = *pprev; | |
145 | goto success; | |
146 | } | |
147 | ||
148 | *pprev = vma; | |
149 | ||
150 | if (start != vma->vm_start) { | |
151 | error = split_vma(mm, vma, start, 1); | |
152 | if (error) | |
153 | goto fail; | |
154 | } | |
155 | ||
156 | if (end != vma->vm_end) { | |
157 | error = split_vma(mm, vma, end, 0); | |
158 | if (error) | |
159 | goto fail; | |
160 | } | |
161 | ||
162 | success: | |
163 | /* | |
164 | * vm_flags and vm_page_prot are protected by the mmap_sem | |
165 | * held in write mode. | |
166 | */ | |
167 | vma->vm_flags = newflags; | |
168 | vma->vm_page_prot = newprot; | |
169 | change_protection(vma, start, end, newprot); | |
ab50b8ed HD |
170 | vm_stat_account(mm, oldflags, vma->vm_file, -nrpages); |
171 | vm_stat_account(mm, newflags, vma->vm_file, nrpages); | |
1da177e4 LT |
172 | return 0; |
173 | ||
174 | fail: | |
175 | vm_unacct_memory(charged); | |
176 | return error; | |
177 | } | |
178 | ||
179 | asmlinkage long | |
180 | sys_mprotect(unsigned long start, size_t len, unsigned long prot) | |
181 | { | |
182 | unsigned long vm_flags, nstart, end, tmp, reqprot; | |
183 | struct vm_area_struct *vma, *prev; | |
184 | int error = -EINVAL; | |
185 | const int grows = prot & (PROT_GROWSDOWN|PROT_GROWSUP); | |
186 | prot &= ~(PROT_GROWSDOWN|PROT_GROWSUP); | |
187 | if (grows == (PROT_GROWSDOWN|PROT_GROWSUP)) /* can't be both */ | |
188 | return -EINVAL; | |
189 | ||
190 | if (start & ~PAGE_MASK) | |
191 | return -EINVAL; | |
192 | if (!len) | |
193 | return 0; | |
194 | len = PAGE_ALIGN(len); | |
195 | end = start + len; | |
196 | if (end <= start) | |
197 | return -ENOMEM; | |
198 | if (prot & ~(PROT_READ | PROT_WRITE | PROT_EXEC | PROT_SEM)) | |
199 | return -EINVAL; | |
200 | ||
201 | reqprot = prot; | |
202 | /* | |
203 | * Does the application expect PROT_READ to imply PROT_EXEC: | |
204 | */ | |
205 | if (unlikely((prot & PROT_READ) && | |
206 | (current->personality & READ_IMPLIES_EXEC))) | |
207 | prot |= PROT_EXEC; | |
208 | ||
209 | vm_flags = calc_vm_prot_bits(prot); | |
210 | ||
211 | down_write(¤t->mm->mmap_sem); | |
212 | ||
213 | vma = find_vma_prev(current->mm, start, &prev); | |
214 | error = -ENOMEM; | |
215 | if (!vma) | |
216 | goto out; | |
217 | if (unlikely(grows & PROT_GROWSDOWN)) { | |
218 | if (vma->vm_start >= end) | |
219 | goto out; | |
220 | start = vma->vm_start; | |
221 | error = -EINVAL; | |
222 | if (!(vma->vm_flags & VM_GROWSDOWN)) | |
223 | goto out; | |
224 | } | |
225 | else { | |
226 | if (vma->vm_start > start) | |
227 | goto out; | |
228 | if (unlikely(grows & PROT_GROWSUP)) { | |
229 | end = vma->vm_end; | |
230 | error = -EINVAL; | |
231 | if (!(vma->vm_flags & VM_GROWSUP)) | |
232 | goto out; | |
233 | } | |
234 | } | |
235 | if (start > vma->vm_start) | |
236 | prev = vma; | |
237 | ||
238 | for (nstart = start ; ; ) { | |
239 | unsigned long newflags; | |
240 | ||
241 | /* Here we know that vma->vm_start <= nstart < vma->vm_end. */ | |
242 | ||
243 | if (is_vm_hugetlb_page(vma)) { | |
244 | error = -EACCES; | |
245 | goto out; | |
246 | } | |
247 | ||
248 | newflags = vm_flags | (vma->vm_flags & ~(VM_READ | VM_WRITE | VM_EXEC)); | |
249 | ||
7e2cff42 PBG |
250 | /* newflags >> 4 shift VM_MAY% in place of VM_% */ |
251 | if ((newflags & ~(newflags >> 4)) & (VM_READ | VM_WRITE | VM_EXEC)) { | |
1da177e4 LT |
252 | error = -EACCES; |
253 | goto out; | |
254 | } | |
255 | ||
256 | error = security_file_mprotect(vma, reqprot, prot); | |
257 | if (error) | |
258 | goto out; | |
259 | ||
260 | tmp = vma->vm_end; | |
261 | if (tmp > end) | |
262 | tmp = end; | |
263 | error = mprotect_fixup(vma, &prev, nstart, tmp, newflags); | |
264 | if (error) | |
265 | goto out; | |
266 | nstart = tmp; | |
267 | ||
268 | if (nstart < prev->vm_end) | |
269 | nstart = prev->vm_end; | |
270 | if (nstart >= end) | |
271 | goto out; | |
272 | ||
273 | vma = prev->vm_next; | |
274 | if (!vma || vma->vm_start != nstart) { | |
275 | error = -ENOMEM; | |
276 | goto out; | |
277 | } | |
278 | } | |
279 | out: | |
280 | up_write(¤t->mm->mmap_sem); | |
281 | return error; | |
282 | } |