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 32 static inline pgprot_t pgprot_modify(pgprot_t oldprot, pgprot_t newprot) 33 { 34 return newprot; 35 } 36 #endif 37 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 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 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 } 112 113 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 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 } 220 221 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