blob: b426f01c5e9cdb0329657076d8a2e8908e3e015a [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
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
28static 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
50static 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
65static 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
80static 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
102static int
103mprotect_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
163success:
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);
Hugh Dickinsab50b8e2005-10-29 18:15:56 -0700171 vm_stat_account(mm, oldflags, vma->vm_file, -nrpages);
172 vm_stat_account(mm, newflags, vma->vm_file, nrpages);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700173 return 0;
174
175fail:
176 vm_unacct_memory(charged);
177 return error;
178}
179
180asmlinkage long
181sys_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(&current->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
Paolo 'Blaisorblade' Giarrusso7e2cff42005-09-21 09:55:39 -0700251 /* newflags >> 4 shift VM_MAY% in place of VM_% */
252 if ((newflags & ~(newflags >> 4)) & (VM_READ | VM_WRITE | VM_EXEC)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700253 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 }
280out:
281 up_write(&current->mm->mmap_sem);
282 return error;
283}