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