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 if (newflags & VM_WRITE) { 158 if (!(oldflags & (VM_ACCOUNT|VM_WRITE| 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 if (is_vm_hugetlb_page(vma)) 207 hugetlb_change_protection(vma, start, end, vma->vm_page_prot); 208 else 209 change_protection(vma, start, end, vma->vm_page_prot, dirty_accountable); 210 vm_stat_account(mm, oldflags, vma->vm_file, -nrpages); 211 vm_stat_account(mm, newflags, vma->vm_file, nrpages); 212 return 0; 213 214 fail: 215 vm_unacct_memory(charged); 216 return error; 217 } 218 219 asmlinkage long 220 sys_mprotect(unsigned long start, size_t len, unsigned long prot) 221 { 222 unsigned long vm_flags, nstart, end, tmp, reqprot; 223 struct vm_area_struct *vma, *prev; 224 int error = -EINVAL; 225 const int grows = prot & (PROT_GROWSDOWN|PROT_GROWSUP); 226 prot &= ~(PROT_GROWSDOWN|PROT_GROWSUP); 227 if (grows == (PROT_GROWSDOWN|PROT_GROWSUP)) /* can't be both */ 228 return -EINVAL; 229 230 if (start & ~PAGE_MASK) 231 return -EINVAL; 232 if (!len) 233 return 0; 234 len = PAGE_ALIGN(len); 235 end = start + len; 236 if (end <= start) 237 return -ENOMEM; 238 if (!arch_validate_prot(prot)) 239 return -EINVAL; 240 241 reqprot = prot; 242 /* 243 * Does the application expect PROT_READ to imply PROT_EXEC: 244 */ 245 if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC)) 246 prot |= PROT_EXEC; 247 248 vm_flags = calc_vm_prot_bits(prot); 249 250 down_write(¤t->mm->mmap_sem); 251 252 vma = find_vma_prev(current->mm, start, &prev); 253 error = -ENOMEM; 254 if (!vma) 255 goto out; 256 if (unlikely(grows & PROT_GROWSDOWN)) { 257 if (vma->vm_start >= end) 258 goto out; 259 start = vma->vm_start; 260 error = -EINVAL; 261 if (!(vma->vm_flags & VM_GROWSDOWN)) 262 goto out; 263 } 264 else { 265 if (vma->vm_start > start) 266 goto out; 267 if (unlikely(grows & PROT_GROWSUP)) { 268 end = vma->vm_end; 269 error = -EINVAL; 270 if (!(vma->vm_flags & VM_GROWSUP)) 271 goto out; 272 } 273 } 274 if (start > vma->vm_start) 275 prev = vma; 276 277 for (nstart = start ; ; ) { 278 unsigned long newflags; 279 280 /* Here we know that vma->vm_start <= nstart < vma->vm_end. */ 281 282 newflags = vm_flags | (vma->vm_flags & ~(VM_READ | VM_WRITE | VM_EXEC)); 283 284 /* newflags >> 4 shift VM_MAY% in place of VM_% */ 285 if ((newflags & ~(newflags >> 4)) & (VM_READ | VM_WRITE | VM_EXEC)) { 286 error = -EACCES; 287 goto out; 288 } 289 290 error = security_file_mprotect(vma, reqprot, prot); 291 if (error) 292 goto out; 293 294 tmp = vma->vm_end; 295 if (tmp > end) 296 tmp = end; 297 error = mprotect_fixup(vma, &prev, nstart, tmp, newflags); 298 if (error) 299 goto out; 300 nstart = tmp; 301 302 if (nstart < prev->vm_end) 303 nstart = prev->vm_end; 304 if (nstart >= end) 305 goto out; 306 307 vma = prev->vm_next; 308 if (!vma || vma->vm_start != nstart) { 309 error = -ENOMEM; 310 goto out; 311 } 312 } 313 out: 314 up_write(¤t->mm->mmap_sem); 315 return error; 316 } 317