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/shm.h> 14 #include <linux/mman.h> 15 #include <linux/fs.h> 16 #include <linux/highmem.h> 17 #include <linux/security.h> 18 #include <linux/mempolicy.h> 19 #include <linux/personality.h> 20 #include <linux/syscalls.h> 21 #include <linux/swap.h> 22 #include <linux/swapops.h> 23 #include <linux/mmu_notifier.h> 24 #include <linux/migrate.h> 25 #include <linux/perf_event.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 unsigned long 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 unsigned long pages = 0; 45 46 pte = pte_offset_map_lock(mm, pmd, addr, &ptl); 47 arch_enter_lazy_mmu_mode(); 48 do { 49 oldpte = *pte; 50 if (pte_present(oldpte)) { 51 pte_t ptent; 52 53 ptent = ptep_modify_prot_start(mm, addr, pte); 54 ptent = pte_modify(ptent, newprot); 55 56 /* 57 * Avoid taking write faults for pages we know to be 58 * dirty. 59 */ 60 if (dirty_accountable && pte_dirty(ptent)) 61 ptent = pte_mkwrite(ptent); 62 63 ptep_modify_prot_commit(mm, addr, pte, ptent); 64 pages++; 65 } else if (IS_ENABLED(CONFIG_MIGRATION) && !pte_file(oldpte)) { 66 swp_entry_t entry = pte_to_swp_entry(oldpte); 67 68 if (is_write_migration_entry(entry)) { 69 /* 70 * A protection check is difficult so 71 * just be safe and disable write 72 */ 73 make_migration_entry_read(&entry); 74 set_pte_at(mm, addr, pte, 75 swp_entry_to_pte(entry)); 76 } 77 pages++; 78 } 79 } while (pte++, addr += PAGE_SIZE, addr != end); 80 arch_leave_lazy_mmu_mode(); 81 pte_unmap_unlock(pte - 1, ptl); 82 83 return pages; 84 } 85 86 static inline unsigned long change_pmd_range(struct vm_area_struct *vma, pud_t *pud, 87 unsigned long addr, unsigned long end, pgprot_t newprot, 88 int dirty_accountable) 89 { 90 pmd_t *pmd; 91 unsigned long next; 92 unsigned long pages = 0; 93 94 pmd = pmd_offset(pud, addr); 95 do { 96 next = pmd_addr_end(addr, end); 97 if (pmd_trans_huge(*pmd)) { 98 if (next - addr != HPAGE_PMD_SIZE) 99 split_huge_page_pmd(vma->vm_mm, pmd); 100 else if (change_huge_pmd(vma, pmd, addr, newprot)) { 101 pages += HPAGE_PMD_NR; 102 continue; 103 } 104 /* fall through */ 105 } 106 if (pmd_none_or_clear_bad(pmd)) 107 continue; 108 pages += change_pte_range(vma->vm_mm, pmd, addr, next, newprot, 109 dirty_accountable); 110 } while (pmd++, addr = next, addr != end); 111 112 return pages; 113 } 114 115 static inline unsigned long change_pud_range(struct vm_area_struct *vma, pgd_t *pgd, 116 unsigned long addr, unsigned long end, pgprot_t newprot, 117 int dirty_accountable) 118 { 119 pud_t *pud; 120 unsigned long next; 121 unsigned long pages = 0; 122 123 pud = pud_offset(pgd, addr); 124 do { 125 next = pud_addr_end(addr, end); 126 if (pud_none_or_clear_bad(pud)) 127 continue; 128 pages += change_pmd_range(vma, pud, addr, next, newprot, 129 dirty_accountable); 130 } while (pud++, addr = next, addr != end); 131 132 return pages; 133 } 134 135 static unsigned long change_protection_range(struct vm_area_struct *vma, 136 unsigned long addr, unsigned long end, pgprot_t newprot, 137 int dirty_accountable) 138 { 139 struct mm_struct *mm = vma->vm_mm; 140 pgd_t *pgd; 141 unsigned long next; 142 unsigned long start = addr; 143 unsigned long pages = 0; 144 145 BUG_ON(addr >= end); 146 pgd = pgd_offset(mm, addr); 147 flush_cache_range(vma, addr, end); 148 do { 149 next = pgd_addr_end(addr, end); 150 if (pgd_none_or_clear_bad(pgd)) 151 continue; 152 pages += change_pud_range(vma, pgd, addr, next, newprot, 153 dirty_accountable); 154 } while (pgd++, addr = next, addr != end); 155 156 flush_tlb_range(vma, start, end); 157 158 return pages; 159 } 160 161 unsigned long change_protection(struct vm_area_struct *vma, unsigned long start, 162 unsigned long end, pgprot_t newprot, 163 int dirty_accountable) 164 { 165 struct mm_struct *mm = vma->vm_mm; 166 unsigned long pages; 167 168 mmu_notifier_invalidate_range_start(mm, start, end); 169 if (is_vm_hugetlb_page(vma)) 170 pages = hugetlb_change_protection(vma, start, end, newprot); 171 else 172 pages = change_protection_range(vma, start, end, newprot, dirty_accountable); 173 mmu_notifier_invalidate_range_end(mm, start, end); 174 175 return pages; 176 } 177 178 int 179 mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev, 180 unsigned long start, unsigned long end, unsigned long newflags) 181 { 182 struct mm_struct *mm = vma->vm_mm; 183 unsigned long oldflags = vma->vm_flags; 184 long nrpages = (end - start) >> PAGE_SHIFT; 185 unsigned long charged = 0; 186 pgoff_t pgoff; 187 int error; 188 int dirty_accountable = 0; 189 190 if (newflags == oldflags) { 191 *pprev = vma; 192 return 0; 193 } 194 195 /* 196 * If we make a private mapping writable we increase our commit; 197 * but (without finer accounting) cannot reduce our commit if we 198 * make it unwritable again. hugetlb mapping were accounted for 199 * even if read-only so there is no need to account for them here 200 */ 201 if (newflags & VM_WRITE) { 202 if (!(oldflags & (VM_ACCOUNT|VM_WRITE|VM_HUGETLB| 203 VM_SHARED|VM_NORESERVE))) { 204 charged = nrpages; 205 if (security_vm_enough_memory_mm(mm, charged)) 206 return -ENOMEM; 207 newflags |= VM_ACCOUNT; 208 } 209 } 210 211 /* 212 * First try to merge with previous and/or next vma. 213 */ 214 pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT); 215 *pprev = vma_merge(mm, *pprev, start, end, newflags, 216 vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma)); 217 if (*pprev) { 218 vma = *pprev; 219 goto success; 220 } 221 222 *pprev = vma; 223 224 if (start != vma->vm_start) { 225 error = split_vma(mm, vma, start, 1); 226 if (error) 227 goto fail; 228 } 229 230 if (end != vma->vm_end) { 231 error = split_vma(mm, vma, end, 0); 232 if (error) 233 goto fail; 234 } 235 236 success: 237 /* 238 * vm_flags and vm_page_prot are protected by the mmap_sem 239 * held in write mode. 240 */ 241 vma->vm_flags = newflags; 242 vma->vm_page_prot = pgprot_modify(vma->vm_page_prot, 243 vm_get_page_prot(newflags)); 244 245 if (vma_wants_writenotify(vma)) { 246 vma->vm_page_prot = vm_get_page_prot(newflags & ~VM_SHARED); 247 dirty_accountable = 1; 248 } 249 250 change_protection(vma, start, end, vma->vm_page_prot, dirty_accountable); 251 252 vm_stat_account(mm, oldflags, vma->vm_file, -nrpages); 253 vm_stat_account(mm, newflags, vma->vm_file, nrpages); 254 perf_event_mmap(vma); 255 return 0; 256 257 fail: 258 vm_unacct_memory(charged); 259 return error; 260 } 261 262 SYSCALL_DEFINE3(mprotect, unsigned long, start, size_t, len, 263 unsigned long, prot) 264 { 265 unsigned long vm_flags, nstart, end, tmp, reqprot; 266 struct vm_area_struct *vma, *prev; 267 int error = -EINVAL; 268 const int grows = prot & (PROT_GROWSDOWN|PROT_GROWSUP); 269 prot &= ~(PROT_GROWSDOWN|PROT_GROWSUP); 270 if (grows == (PROT_GROWSDOWN|PROT_GROWSUP)) /* can't be both */ 271 return -EINVAL; 272 273 if (start & ~PAGE_MASK) 274 return -EINVAL; 275 if (!len) 276 return 0; 277 len = PAGE_ALIGN(len); 278 end = start + len; 279 if (end <= start) 280 return -ENOMEM; 281 if (!arch_validate_prot(prot)) 282 return -EINVAL; 283 284 reqprot = prot; 285 /* 286 * Does the application expect PROT_READ to imply PROT_EXEC: 287 */ 288 if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC)) 289 prot |= PROT_EXEC; 290 291 vm_flags = calc_vm_prot_bits(prot); 292 293 down_write(¤t->mm->mmap_sem); 294 295 vma = find_vma(current->mm, start); 296 error = -ENOMEM; 297 if (!vma) 298 goto out; 299 prev = vma->vm_prev; 300 if (unlikely(grows & PROT_GROWSDOWN)) { 301 if (vma->vm_start >= end) 302 goto out; 303 start = vma->vm_start; 304 error = -EINVAL; 305 if (!(vma->vm_flags & VM_GROWSDOWN)) 306 goto out; 307 } 308 else { 309 if (vma->vm_start > start) 310 goto out; 311 if (unlikely(grows & PROT_GROWSUP)) { 312 end = vma->vm_end; 313 error = -EINVAL; 314 if (!(vma->vm_flags & VM_GROWSUP)) 315 goto out; 316 } 317 } 318 if (start > vma->vm_start) 319 prev = vma; 320 321 for (nstart = start ; ; ) { 322 unsigned long newflags; 323 324 /* Here we know that vma->vm_start <= nstart < vma->vm_end. */ 325 326 newflags = vm_flags | (vma->vm_flags & ~(VM_READ | VM_WRITE | VM_EXEC)); 327 328 /* newflags >> 4 shift VM_MAY% in place of VM_% */ 329 if ((newflags & ~(newflags >> 4)) & (VM_READ | VM_WRITE | VM_EXEC)) { 330 error = -EACCES; 331 goto out; 332 } 333 334 error = security_file_mprotect(vma, reqprot, prot); 335 if (error) 336 goto out; 337 338 tmp = vma->vm_end; 339 if (tmp > end) 340 tmp = end; 341 error = mprotect_fixup(vma, &prev, nstart, tmp, newflags); 342 if (error) 343 goto out; 344 nstart = tmp; 345 346 if (nstart < prev->vm_end) 347 nstart = prev->vm_end; 348 if (nstart >= end) 349 goto out; 350 351 vma = prev->vm_next; 352 if (!vma || vma->vm_start != nstart) { 353 error = -ENOMEM; 354 goto out; 355 } 356 } 357 out: 358 up_write(¤t->mm->mmap_sem); 359 return error; 360 } 361