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@lxorguk.ukuu.org.uk>
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 #include <linux/swap.h>
23 #include <linux/swapops.h>
24 #include <linux/mmu_notifier.h>
25 #include <linux/migrate.h>
26 #include <linux/perf_counter.h>
27 #include <asm/uaccess.h>
28 #include <asm/pgtable.h>
29 #include <asm/cacheflush.h>
30 #include <asm/tlbflush.h>
31
32 #ifndef pgprot_modify
33 static inline pgprot_t pgprot_modify(pgprot_t oldprot, pgprot_t newprot)
34 {
35 return newprot;
36 }
37 #endif
38
39 static void change_pte_range(struct mm_struct *mm, pmd_t *pmd,
40 unsigned long addr, unsigned long end, pgprot_t newprot,
41 int dirty_accountable)
42 {
43 pte_t *pte, oldpte;
44 spinlock_t *ptl;
45
46 pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
47 arch_enter_lazy_mmu_mode();
48 do {
49 oldpte = *pte;
50 if (pte_present(oldpte)) {
51 pte_t ptent;
52
53 ptent = ptep_modify_prot_start(mm, addr, pte);
54 ptent = pte_modify(ptent, newprot);
55
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);
62
63 ptep_modify_prot_commit(mm, addr, pte, ptent);
64 } else if (PAGE_MIGRATION && !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 }
77 } while (pte++, addr += PAGE_SIZE, addr != end);
78 arch_leave_lazy_mmu_mode();
79 pte_unmap_unlock(pte - 1, ptl);
80 }
81
82 static inline void change_pmd_range(struct mm_struct *mm, pud_t *pud,
83 unsigned long addr, unsigned long end, pgprot_t newprot,
84 int dirty_accountable)
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;
94 change_pte_range(mm, pmd, addr, next, newprot, dirty_accountable);
95 } while (pmd++, addr = next, addr != end);
96 }
97
98 static inline void change_pud_range(struct mm_struct *mm, pgd_t *pgd,
99 unsigned long addr, unsigned long end, pgprot_t newprot,
100 int dirty_accountable)
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;
110 change_pmd_range(mm, pud, addr, next, newprot, dirty_accountable);
111 } while (pud++, addr = next, addr != end);
112 }
113
114 static void change_protection(struct vm_area_struct *vma,
115 unsigned long addr, unsigned long end, pgprot_t newprot,
116 int dirty_accountable)
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);
126 do {
127 next = pgd_addr_end(addr, end);
128 if (pgd_none_or_clear_bad(pgd))
129 continue;
130 change_pud_range(mm, pgd, addr, next, newprot, dirty_accountable);
131 } while (pgd++, addr = next, addr != end);
132 flush_tlb_range(vma, start, end);
133 }
134
135 int
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;
143 pgoff_t pgoff;
144 int error;
145 int dirty_accountable = 0;
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. hugetlb mapping were accounted for
156 * even if read-only so there is no need to account for them here
157 */
158 if (newflags & VM_WRITE) {
159 if (!(oldflags & (VM_ACCOUNT|VM_WRITE|VM_HUGETLB|
160 VM_SHARED|VM_NORESERVE))) {
161 charged = nrpages;
162 if (security_vm_enough_memory(charged))
163 return -ENOMEM;
164 newflags |= VM_ACCOUNT;
165 }
166 }
167
168 /*
169 * First try to merge with previous and/or next vma.
170 */
171 pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
172 *pprev = vma_merge(mm, *pprev, start, end, newflags,
173 vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma));
174 if (*pprev) {
175 vma = *pprev;
176 goto success;
177 }
178
179 *pprev = vma;
180
181 if (start != vma->vm_start) {
182 error = split_vma(mm, vma, start, 1);
183 if (error)
184 goto fail;
185 }
186
187 if (end != vma->vm_end) {
188 error = split_vma(mm, vma, end, 0);
189 if (error)
190 goto fail;
191 }
192
193 success:
194 /*
195 * vm_flags and vm_page_prot are protected by the mmap_sem
196 * held in write mode.
197 */
198 vma->vm_flags = newflags;
199 vma->vm_page_prot = pgprot_modify(vma->vm_page_prot,
200 vm_get_page_prot(newflags));
201
202 if (vma_wants_writenotify(vma)) {
203 vma->vm_page_prot = vm_get_page_prot(newflags & ~VM_SHARED);
204 dirty_accountable = 1;
205 }
206
207 mmu_notifier_invalidate_range_start(mm, start, end);
208 if (is_vm_hugetlb_page(vma))
209 hugetlb_change_protection(vma, start, end, vma->vm_page_prot);
210 else
211 change_protection(vma, start, end, vma->vm_page_prot, dirty_accountable);
212 mmu_notifier_invalidate_range_end(mm, start, end);
213 vm_stat_account(mm, oldflags, vma->vm_file, -nrpages);
214 vm_stat_account(mm, newflags, vma->vm_file, nrpages);
215 return 0;
216
217 fail:
218 vm_unacct_memory(charged);
219 return error;
220 }
221
222 SYSCALL_DEFINE3(mprotect, unsigned long, start, size_t, len,
223 unsigned long, prot)
224 {
225 unsigned long vm_flags, nstart, end, tmp, reqprot;
226 struct vm_area_struct *vma, *prev;
227 int error = -EINVAL;
228 const int grows = prot & (PROT_GROWSDOWN|PROT_GROWSUP);
229 prot &= ~(PROT_GROWSDOWN|PROT_GROWSUP);
230 if (grows == (PROT_GROWSDOWN|PROT_GROWSUP)) /* can't be both */
231 return -EINVAL;
232
233 if (start & ~PAGE_MASK)
234 return -EINVAL;
235 if (!len)
236 return 0;
237 len = PAGE_ALIGN(len);
238 end = start + len;
239 if (end <= start)
240 return -ENOMEM;
241 if (!arch_validate_prot(prot))
242 return -EINVAL;
243
244 reqprot = prot;
245 /*
246 * Does the application expect PROT_READ to imply PROT_EXEC:
247 */
248 if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC))
249 prot |= PROT_EXEC;
250
251 vm_flags = calc_vm_prot_bits(prot);
252
253 down_write(¤t->mm->mmap_sem);
254
255 vma = find_vma_prev(current->mm, start, &prev);
256 error = -ENOMEM;
257 if (!vma)
258 goto out;
259 if (unlikely(grows & PROT_GROWSDOWN)) {
260 if (vma->vm_start >= end)
261 goto out;
262 start = vma->vm_start;
263 error = -EINVAL;
264 if (!(vma->vm_flags & VM_GROWSDOWN))
265 goto out;
266 }
267 else {
268 if (vma->vm_start > start)
269 goto out;
270 if (unlikely(grows & PROT_GROWSUP)) {
271 end = vma->vm_end;
272 error = -EINVAL;
273 if (!(vma->vm_flags & VM_GROWSUP))
274 goto out;
275 }
276 }
277 if (start > vma->vm_start)
278 prev = vma;
279
280 for (nstart = start ; ; ) {
281 unsigned long newflags;
282
283 /* Here we know that vma->vm_start <= nstart < vma->vm_end. */
284
285 newflags = vm_flags | (vma->vm_flags & ~(VM_READ | VM_WRITE | VM_EXEC));
286
287 /* newflags >> 4 shift VM_MAY% in place of VM_% */
288 if ((newflags & ~(newflags >> 4)) & (VM_READ | VM_WRITE | VM_EXEC)) {
289 error = -EACCES;
290 goto out;
291 }
292
293 error = security_file_mprotect(vma, reqprot, prot);
294 if (error)
295 goto out;
296
297 tmp = vma->vm_end;
298 if (tmp > end)
299 tmp = end;
300 error = mprotect_fixup(vma, &prev, nstart, tmp, newflags);
301 if (error)
302 goto out;
303 perf_counter_mmap(vma);
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 }
321
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