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 <asm/uaccess.h>
27 #include <asm/pgtable.h>
28 #include <asm/cacheflush.h>
29 #include <asm/tlbflush.h>
30
31 #ifndef pgprot_modify
pgprot_modify(pgprot_t oldprot,pgprot_t newprot)32 static inline pgprot_t pgprot_modify(pgprot_t oldprot, pgprot_t newprot)
33 {
34 return newprot;
35 }
36 #endif
37
change_pte_range(struct mm_struct * mm,pmd_t * pmd,unsigned long addr,unsigned long end,pgprot_t newprot,int dirty_accountable)38 static void change_pte_range(struct mm_struct *mm, pmd_t *pmd,
39 unsigned long addr, unsigned long end, pgprot_t newprot,
40 int dirty_accountable)
41 {
42 pte_t *pte, oldpte;
43 spinlock_t *ptl;
44
45 pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
46 arch_enter_lazy_mmu_mode();
47 do {
48 oldpte = *pte;
49 if (pte_present(oldpte)) {
50 pte_t ptent;
51
52 ptent = ptep_modify_prot_start(mm, addr, pte);
53 ptent = pte_modify(ptent, newprot);
54
55 /*
56 * Avoid taking write faults for pages we know to be
57 * dirty.
58 */
59 if (dirty_accountable && pte_dirty(ptent))
60 ptent = pte_mkwrite(ptent);
61
62 ptep_modify_prot_commit(mm, addr, pte, ptent);
63 } else if (PAGE_MIGRATION && !pte_file(oldpte)) {
64 swp_entry_t entry = pte_to_swp_entry(oldpte);
65
66 if (is_write_migration_entry(entry)) {
67 /*
68 * A protection check is difficult so
69 * just be safe and disable write
70 */
71 make_migration_entry_read(&entry);
72 set_pte_at(mm, addr, pte,
73 swp_entry_to_pte(entry));
74 }
75 }
76 } while (pte++, addr += PAGE_SIZE, addr != end);
77 arch_leave_lazy_mmu_mode();
78 pte_unmap_unlock(pte - 1, ptl);
79 }
80
change_pmd_range(struct mm_struct * mm,pud_t * pud,unsigned long addr,unsigned long end,pgprot_t newprot,int dirty_accountable)81 static inline void change_pmd_range(struct mm_struct *mm, pud_t *pud,
82 unsigned long addr, unsigned long end, pgprot_t newprot,
83 int dirty_accountable)
84 {
85 pmd_t *pmd;
86 unsigned long next;
87
88 pmd = pmd_offset(pud, addr);
89 do {
90 next = pmd_addr_end(addr, end);
91 if (pmd_none_or_clear_bad(pmd))
92 continue;
93 change_pte_range(mm, pmd, addr, next, newprot, dirty_accountable);
94 } while (pmd++, addr = next, addr != end);
95 }
96
change_pud_range(struct mm_struct * mm,pgd_t * pgd,unsigned long addr,unsigned long end,pgprot_t newprot,int dirty_accountable)97 static inline void change_pud_range(struct mm_struct *mm, pgd_t *pgd,
98 unsigned long addr, unsigned long end, pgprot_t newprot,
99 int dirty_accountable)
100 {
101 pud_t *pud;
102 unsigned long next;
103
104 pud = pud_offset(pgd, addr);
105 do {
106 next = pud_addr_end(addr, end);
107 if (pud_none_or_clear_bad(pud))
108 continue;
109 change_pmd_range(mm, pud, addr, next, newprot, dirty_accountable);
110 } while (pud++, addr = next, addr != end);
111 }
112
change_protection(struct vm_area_struct * vma,unsigned long addr,unsigned long end,pgprot_t newprot,int dirty_accountable)113 static void change_protection(struct vm_area_struct *vma,
114 unsigned long addr, unsigned long end, pgprot_t newprot,
115 int dirty_accountable)
116 {
117 struct mm_struct *mm = vma->vm_mm;
118 pgd_t *pgd;
119 unsigned long next;
120 unsigned long start = addr;
121
122 BUG_ON(addr >= end);
123 pgd = pgd_offset(mm, addr);
124 flush_cache_range(vma, addr, end);
125 do {
126 next = pgd_addr_end(addr, end);
127 if (pgd_none_or_clear_bad(pgd))
128 continue;
129 change_pud_range(mm, pgd, addr, next, newprot, dirty_accountable);
130 } while (pgd++, addr = next, addr != end);
131 flush_tlb_range(vma, start, end);
132 }
133
134 int
mprotect_fixup(struct vm_area_struct * vma,struct vm_area_struct ** pprev,unsigned long start,unsigned long end,unsigned long newflags)135 mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev,
136 unsigned long start, unsigned long end, unsigned long newflags)
137 {
138 struct mm_struct *mm = vma->vm_mm;
139 unsigned long oldflags = vma->vm_flags;
140 long nrpages = (end - start) >> PAGE_SHIFT;
141 unsigned long charged = 0;
142 pgoff_t pgoff;
143 int error;
144 int dirty_accountable = 0;
145
146 if (newflags == oldflags) {
147 *pprev = vma;
148 return 0;
149 }
150
151 /*
152 * If we make a private mapping writable we increase our commit;
153 * but (without finer accounting) cannot reduce our commit if we
154 * make it unwritable again. hugetlb mapping were accounted for
155 * even if read-only so there is no need to account for them here
156 */
157 if (newflags & VM_WRITE) {
158 if (!(oldflags & (VM_ACCOUNT|VM_WRITE|VM_HUGETLB|
159 VM_SHARED|VM_NORESERVE))) {
160 charged = nrpages;
161 if (security_vm_enough_memory(charged))
162 return -ENOMEM;
163 newflags |= VM_ACCOUNT;
164 }
165 }
166
167 /*
168 * First try to merge with previous and/or next vma.
169 */
170 pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
171 *pprev = vma_merge(mm, *pprev, start, end, newflags,
172 vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma));
173 if (*pprev) {
174 vma = *pprev;
175 goto success;
176 }
177
178 *pprev = vma;
179
180 if (start != vma->vm_start) {
181 error = split_vma(mm, vma, start, 1);
182 if (error)
183 goto fail;
184 }
185
186 if (end != vma->vm_end) {
187 error = split_vma(mm, vma, end, 0);
188 if (error)
189 goto fail;
190 }
191
192 success:
193 /*
194 * vm_flags and vm_page_prot are protected by the mmap_sem
195 * held in write mode.
196 */
197 vma->vm_flags = newflags;
198 vma->vm_page_prot = pgprot_modify(vma->vm_page_prot,
199 vm_get_page_prot(newflags));
200
201 if (vma_wants_writenotify(vma)) {
202 vma->vm_page_prot = vm_get_page_prot(newflags & ~VM_SHARED);
203 dirty_accountable = 1;
204 }
205
206 mmu_notifier_invalidate_range_start(mm, start, end);
207 if (is_vm_hugetlb_page(vma))
208 hugetlb_change_protection(vma, start, end, vma->vm_page_prot);
209 else
210 change_protection(vma, start, end, vma->vm_page_prot, dirty_accountable);
211 mmu_notifier_invalidate_range_end(mm, start, end);
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
SYSCALL_DEFINE3(mprotect,unsigned long,start,size_t,len,unsigned long,prot)221 SYSCALL_DEFINE3(mprotect, unsigned long, start, size_t, len,
222 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(¤t->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(¤t->mm->mmap_sem);
317 return error;
318 }
319