360d9cc8b38c061185d562fc40b7f032ae34d21d
[linux-2.6.git] / mm / mprotect.c
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 #include <linux/swap.h>
23 #include <linux/swapops.h>
24 #include <asm/uaccess.h>
25 #include <asm/pgtable.h>
26 #include <asm/cacheflush.h>
27 #include <asm/tlbflush.h>
28
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
36 static void change_pte_range(struct mm_struct *mm, pmd_t *pmd,
37                 unsigned long addr, unsigned long end, pgprot_t newprot,
38                 int dirty_accountable)
39 {
40         pte_t *pte, oldpte;
41         spinlock_t *ptl;
42
43         pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
44         arch_enter_lazy_mmu_mode();
45         do {
46                 oldpte = *pte;
47                 if (pte_present(oldpte)) {
48                         pte_t ptent;
49
50                         ptent = ptep_modify_prot_start(mm, addr, pte);
51                         ptent = pte_modify(ptent, newprot);
52
53                         /*
54                          * Avoid taking write faults for pages we know to be
55                          * dirty.
56                          */
57                         if (dirty_accountable && pte_dirty(ptent))
58                                 ptent = pte_mkwrite(ptent);
59
60                         ptep_modify_prot_commit(mm, addr, pte, ptent);
61 #ifdef CONFIG_MIGRATION
62                 } else if (!pte_file(oldpte)) {
63                         swp_entry_t entry = pte_to_swp_entry(oldpte);
64
65                         if (is_write_migration_entry(entry)) {
66                                 /*
67                                  * A protection check is difficult so
68                                  * just be safe and disable write
69                                  */
70                                 make_migration_entry_read(&entry);
71                                 set_pte_at(mm, addr, pte,
72                                         swp_entry_to_pte(entry));
73                         }
74 #endif
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.
156          *
157          * FIXME? We haven't defined a VM_NORESERVE flag, so mprotecting
158          * a MAP_NORESERVE private mapping to writable will now reserve.
159          */
160         if (newflags & VM_WRITE) {
161                 if (!(oldflags & (VM_ACCOUNT|VM_WRITE|VM_SHARED))) {
162                         charged = nrpages;
163                         if (security_vm_enough_memory(charged))
164                                 return -ENOMEM;
165                         newflags |= VM_ACCOUNT;
166                 }
167         }
168
169         /*
170          * First try to merge with previous and/or next vma.
171          */
172         pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
173         *pprev = vma_merge(mm, *pprev, start, end, newflags,
174                         vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma));
175         if (*pprev) {
176                 vma = *pprev;
177                 goto success;
178         }
179
180         *pprev = vma;
181
182         if (start != vma->vm_start) {
183                 error = split_vma(mm, vma, start, 1);
184                 if (error)
185                         goto fail;
186         }
187
188         if (end != vma->vm_end) {
189                 error = split_vma(mm, vma, end, 0);
190                 if (error)
191                         goto fail;
192         }
193
194 success:
195         /*
196          * vm_flags and vm_page_prot are protected by the mmap_sem
197          * held in write mode.
198          */
199         vma->vm_flags = newflags;
200         vma->vm_page_prot = pgprot_modify(vma->vm_page_prot,
201                                           vm_get_page_prot(newflags));
202
203         if (vma_wants_writenotify(vma)) {
204                 vma->vm_page_prot = vm_get_page_prot(newflags & ~VM_SHARED);
205                 dirty_accountable = 1;
206         }
207
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         vm_stat_account(mm, oldflags, vma->vm_file, -nrpages);
213         vm_stat_account(mm, newflags, vma->vm_file, nrpages);
214         return 0;
215
216 fail:
217         vm_unacct_memory(charged);
218         return error;
219 }
220
221 asmlinkage long
222 sys_mprotect(unsigned long start, size_t len, unsigned long prot)
223 {
224         unsigned long vm_flags, nstart, end, tmp, reqprot;
225         struct vm_area_struct *vma, *prev;
226         int error = -EINVAL;
227         const int grows = prot & (PROT_GROWSDOWN|PROT_GROWSUP);
228         prot &= ~(PROT_GROWSDOWN|PROT_GROWSUP);
229         if (grows == (PROT_GROWSDOWN|PROT_GROWSUP)) /* can't be both */
230                 return -EINVAL;
231
232         if (start & ~PAGE_MASK)
233                 return -EINVAL;
234         if (!len)
235                 return 0;
236         len = PAGE_ALIGN(len);
237         end = start + len;
238         if (end <= start)
239                 return -ENOMEM;
240         if (!arch_validate_prot(prot))
241                 return -EINVAL;
242
243         reqprot = prot;
244         /*
245          * Does the application expect PROT_READ to imply PROT_EXEC:
246          */
247         if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC))
248                 prot |= PROT_EXEC;
249
250         vm_flags = calc_vm_prot_bits(prot);
251
252         down_write(&current->mm->mmap_sem);
253
254         vma = find_vma_prev(current->mm, start, &prev);
255         error = -ENOMEM;
256         if (!vma)
257                 goto out;
258         if (unlikely(grows & PROT_GROWSDOWN)) {
259                 if (vma->vm_start >= end)
260                         goto out;
261                 start = vma->vm_start;
262                 error = -EINVAL;
263                 if (!(vma->vm_flags & VM_GROWSDOWN))
264                         goto out;
265         }
266         else {
267                 if (vma->vm_start > start)
268                         goto out;
269                 if (unlikely(grows & PROT_GROWSUP)) {
270                         end = vma->vm_end;
271                         error = -EINVAL;
272                         if (!(vma->vm_flags & VM_GROWSUP))
273                                 goto out;
274                 }
275         }
276         if (start > vma->vm_start)
277                 prev = vma;
278
279         for (nstart = start ; ; ) {
280                 unsigned long newflags;
281
282                 /* Here we know that  vma->vm_start <= nstart < vma->vm_end. */
283
284                 newflags = vm_flags | (vma->vm_flags & ~(VM_READ | VM_WRITE | VM_EXEC));
285
286                 /* newflags >> 4 shift VM_MAY% in place of VM_% */
287                 if ((newflags & ~(newflags >> 4)) & (VM_READ | VM_WRITE | VM_EXEC)) {
288                         error = -EACCES;
289                         goto out;
290                 }
291
292                 error = security_file_mprotect(vma, reqprot, prot);
293                 if (error)
294                         goto out;
295
296                 tmp = vma->vm_end;
297                 if (tmp > end)
298                         tmp = end;
299                 error = mprotect_fixup(vma, &prev, nstart, tmp, newflags);
300                 if (error)
301                         goto out;
302                 nstart = tmp;
303
304                 if (nstart < prev->vm_end)
305                         nstart = prev->vm_end;
306                 if (nstart >= end)
307                         goto out;
308
309                 vma = prev->vm_next;
310                 if (!vma || vma->vm_start != nstart) {
311                         error = -ENOMEM;
312                         goto out;
313                 }
314         }
315 out:
316         up_write(&current->mm->mmap_sem);
317         return error;
318 }