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 <linux/ksm.h> 27 #include <asm/uaccess.h> 28 #include <asm/pgtable.h> 29 #include <asm/cacheflush.h> 30 #include <asm/tlbflush.h> 31 32 #include "internal.h" 33 34 /* 35 * For a prot_numa update we only hold mmap_sem for read so there is a 36 * potential race with faulting where a pmd was temporarily none. This 37 * function checks for a transhuge pmd under the appropriate lock. It 38 * returns a pte if it was successfully locked or NULL if it raced with 39 * a transhuge insertion. 40 */ 41 static pte_t *lock_pte_protection(struct vm_area_struct *vma, pmd_t *pmd, 42 unsigned long addr, int prot_numa, spinlock_t **ptl) 43 { 44 pte_t *pte; 45 spinlock_t *pmdl; 46 47 /* !prot_numa is protected by mmap_sem held for write */ 48 if (!prot_numa) 49 return pte_offset_map_lock(vma->vm_mm, pmd, addr, ptl); 50 51 pmdl = pmd_lock(vma->vm_mm, pmd); 52 if (unlikely(pmd_trans_huge(*pmd) || pmd_none(*pmd))) { 53 spin_unlock(pmdl); 54 return NULL; 55 } 56 57 pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, ptl); 58 spin_unlock(pmdl); 59 return pte; 60 } 61 62 static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd, 63 unsigned long addr, unsigned long end, pgprot_t newprot, 64 int dirty_accountable, int prot_numa) 65 { 66 struct mm_struct *mm = vma->vm_mm; 67 pte_t *pte, oldpte; 68 spinlock_t *ptl; 69 unsigned long pages = 0; 70 71 pte = lock_pte_protection(vma, pmd, addr, prot_numa, &ptl); 72 if (!pte) 73 return 0; 74 75 arch_enter_lazy_mmu_mode(); 76 do { 77 oldpte = *pte; 78 if (pte_present(oldpte)) { 79 pte_t ptent; 80 bool preserve_write = prot_numa && pte_write(oldpte); 81 82 /* 83 * Avoid trapping faults against the zero or KSM 84 * pages. See similar comment in change_huge_pmd. 85 */ 86 if (prot_numa) { 87 struct page *page; 88 89 page = vm_normal_page(vma, addr, oldpte); 90 if (!page || PageKsm(page)) 91 continue; 92 93 /* Avoid TLB flush if possible */ 94 if (pte_protnone(oldpte)) 95 continue; 96 } 97 98 ptent = ptep_modify_prot_start(mm, addr, pte); 99 ptent = pte_modify(ptent, newprot); 100 if (preserve_write) 101 ptent = pte_mkwrite(ptent); 102 103 /* Avoid taking write faults for known dirty pages */ 104 if (dirty_accountable && pte_dirty(ptent) && 105 (pte_soft_dirty(ptent) || 106 !(vma->vm_flags & VM_SOFTDIRTY))) { 107 ptent = pte_mkwrite(ptent); 108 } 109 ptep_modify_prot_commit(mm, addr, pte, ptent); 110 pages++; 111 } else if (IS_ENABLED(CONFIG_MIGRATION)) { 112 swp_entry_t entry = pte_to_swp_entry(oldpte); 113 114 if (is_write_migration_entry(entry)) { 115 pte_t newpte; 116 /* 117 * A protection check is difficult so 118 * just be safe and disable write 119 */ 120 make_migration_entry_read(&entry); 121 newpte = swp_entry_to_pte(entry); 122 if (pte_swp_soft_dirty(oldpte)) 123 newpte = pte_swp_mksoft_dirty(newpte); 124 set_pte_at(mm, addr, pte, newpte); 125 126 pages++; 127 } 128 } 129 } while (pte++, addr += PAGE_SIZE, addr != end); 130 arch_leave_lazy_mmu_mode(); 131 pte_unmap_unlock(pte - 1, ptl); 132 133 return pages; 134 } 135 136 static inline unsigned long change_pmd_range(struct vm_area_struct *vma, 137 pud_t *pud, unsigned long addr, unsigned long end, 138 pgprot_t newprot, int dirty_accountable, int prot_numa) 139 { 140 pmd_t *pmd; 141 struct mm_struct *mm = vma->vm_mm; 142 unsigned long next; 143 unsigned long pages = 0; 144 unsigned long nr_huge_updates = 0; 145 unsigned long mni_start = 0; 146 147 pmd = pmd_offset(pud, addr); 148 do { 149 unsigned long this_pages; 150 151 next = pmd_addr_end(addr, end); 152 if (!pmd_trans_huge(*pmd) && pmd_none_or_clear_bad(pmd)) 153 continue; 154 155 /* invoke the mmu notifier if the pmd is populated */ 156 if (!mni_start) { 157 mni_start = addr; 158 mmu_notifier_invalidate_range_start(mm, mni_start, end); 159 } 160 161 if (pmd_trans_huge(*pmd)) { 162 if (next - addr != HPAGE_PMD_SIZE) 163 split_huge_page_pmd(vma, addr, pmd); 164 else { 165 int nr_ptes = change_huge_pmd(vma, pmd, addr, 166 newprot, prot_numa); 167 168 if (nr_ptes) { 169 if (nr_ptes == HPAGE_PMD_NR) { 170 pages += HPAGE_PMD_NR; 171 nr_huge_updates++; 172 } 173 174 /* huge pmd was handled */ 175 continue; 176 } 177 } 178 /* fall through, the trans huge pmd just split */ 179 } 180 this_pages = change_pte_range(vma, pmd, addr, next, newprot, 181 dirty_accountable, prot_numa); 182 pages += this_pages; 183 } while (pmd++, addr = next, addr != end); 184 185 if (mni_start) 186 mmu_notifier_invalidate_range_end(mm, mni_start, end); 187 188 if (nr_huge_updates) 189 count_vm_numa_events(NUMA_HUGE_PTE_UPDATES, nr_huge_updates); 190 return pages; 191 } 192 193 static inline unsigned long change_pud_range(struct vm_area_struct *vma, 194 pgd_t *pgd, unsigned long addr, unsigned long end, 195 pgprot_t newprot, int dirty_accountable, int prot_numa) 196 { 197 pud_t *pud; 198 unsigned long next; 199 unsigned long pages = 0; 200 201 pud = pud_offset(pgd, addr); 202 do { 203 next = pud_addr_end(addr, end); 204 if (pud_none_or_clear_bad(pud)) 205 continue; 206 pages += change_pmd_range(vma, pud, addr, next, newprot, 207 dirty_accountable, prot_numa); 208 } while (pud++, addr = next, addr != end); 209 210 return pages; 211 } 212 213 static unsigned long change_protection_range(struct vm_area_struct *vma, 214 unsigned long addr, unsigned long end, pgprot_t newprot, 215 int dirty_accountable, int prot_numa) 216 { 217 struct mm_struct *mm = vma->vm_mm; 218 pgd_t *pgd; 219 unsigned long next; 220 unsigned long start = addr; 221 unsigned long pages = 0; 222 223 BUG_ON(addr >= end); 224 pgd = pgd_offset(mm, addr); 225 flush_cache_range(vma, addr, end); 226 set_tlb_flush_pending(mm); 227 do { 228 next = pgd_addr_end(addr, end); 229 if (pgd_none_or_clear_bad(pgd)) 230 continue; 231 pages += change_pud_range(vma, pgd, addr, next, newprot, 232 dirty_accountable, prot_numa); 233 } while (pgd++, addr = next, addr != end); 234 235 /* Only flush the TLB if we actually modified any entries: */ 236 if (pages) 237 flush_tlb_range(vma, start, end); 238 clear_tlb_flush_pending(mm); 239 240 return pages; 241 } 242 243 unsigned long change_protection(struct vm_area_struct *vma, unsigned long start, 244 unsigned long end, pgprot_t newprot, 245 int dirty_accountable, int prot_numa) 246 { 247 unsigned long pages; 248 249 if (is_vm_hugetlb_page(vma)) 250 pages = hugetlb_change_protection(vma, start, end, newprot); 251 else 252 pages = change_protection_range(vma, start, end, newprot, dirty_accountable, prot_numa); 253 254 return pages; 255 } 256 257 int 258 mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev, 259 unsigned long start, unsigned long end, unsigned long newflags) 260 { 261 struct mm_struct *mm = vma->vm_mm; 262 unsigned long oldflags = vma->vm_flags; 263 long nrpages = (end - start) >> PAGE_SHIFT; 264 unsigned long charged = 0; 265 pgoff_t pgoff; 266 int error; 267 int dirty_accountable = 0; 268 269 if (newflags == oldflags) { 270 *pprev = vma; 271 return 0; 272 } 273 274 /* 275 * If we make a private mapping writable we increase our commit; 276 * but (without finer accounting) cannot reduce our commit if we 277 * make it unwritable again. hugetlb mapping were accounted for 278 * even if read-only so there is no need to account for them here 279 */ 280 if (newflags & VM_WRITE) { 281 if (!(oldflags & (VM_ACCOUNT|VM_WRITE|VM_HUGETLB| 282 VM_SHARED|VM_NORESERVE))) { 283 charged = nrpages; 284 if (security_vm_enough_memory_mm(mm, charged)) 285 return -ENOMEM; 286 newflags |= VM_ACCOUNT; 287 } 288 } 289 290 /* 291 * First try to merge with previous and/or next vma. 292 */ 293 pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT); 294 *pprev = vma_merge(mm, *pprev, start, end, newflags, 295 vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma)); 296 if (*pprev) { 297 vma = *pprev; 298 goto success; 299 } 300 301 *pprev = vma; 302 303 if (start != vma->vm_start) { 304 error = split_vma(mm, vma, start, 1); 305 if (error) 306 goto fail; 307 } 308 309 if (end != vma->vm_end) { 310 error = split_vma(mm, vma, end, 0); 311 if (error) 312 goto fail; 313 } 314 315 success: 316 /* 317 * vm_flags and vm_page_prot are protected by the mmap_sem 318 * held in write mode. 319 */ 320 vma->vm_flags = newflags; 321 dirty_accountable = vma_wants_writenotify(vma); 322 vma_set_page_prot(vma); 323 324 change_protection(vma, start, end, vma->vm_page_prot, 325 dirty_accountable, 0); 326 327 /* 328 * Private VM_LOCKED VMA becoming writable: trigger COW to avoid major 329 * fault on access. 330 */ 331 if ((oldflags & (VM_WRITE | VM_SHARED | VM_LOCKED)) == VM_LOCKED && 332 (newflags & VM_WRITE)) { 333 populate_vma_page_range(vma, start, end, NULL); 334 } 335 336 vm_stat_account(mm, oldflags, vma->vm_file, -nrpages); 337 vm_stat_account(mm, newflags, vma->vm_file, nrpages); 338 perf_event_mmap(vma); 339 return 0; 340 341 fail: 342 vm_unacct_memory(charged); 343 return error; 344 } 345 346 SYSCALL_DEFINE3(mprotect, unsigned long, start, size_t, len, 347 unsigned long, prot) 348 { 349 unsigned long vm_flags, nstart, end, tmp, reqprot; 350 struct vm_area_struct *vma, *prev; 351 int error = -EINVAL; 352 const int grows = prot & (PROT_GROWSDOWN|PROT_GROWSUP); 353 prot &= ~(PROT_GROWSDOWN|PROT_GROWSUP); 354 if (grows == (PROT_GROWSDOWN|PROT_GROWSUP)) /* can't be both */ 355 return -EINVAL; 356 357 if (start & ~PAGE_MASK) 358 return -EINVAL; 359 if (!len) 360 return 0; 361 len = PAGE_ALIGN(len); 362 end = start + len; 363 if (end <= start) 364 return -ENOMEM; 365 if (!arch_validate_prot(prot)) 366 return -EINVAL; 367 368 reqprot = prot; 369 /* 370 * Does the application expect PROT_READ to imply PROT_EXEC: 371 */ 372 if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC)) 373 prot |= PROT_EXEC; 374 375 vm_flags = calc_vm_prot_bits(prot); 376 377 down_write(¤t->mm->mmap_sem); 378 379 vma = find_vma(current->mm, start); 380 error = -ENOMEM; 381 if (!vma) 382 goto out; 383 prev = vma->vm_prev; 384 if (unlikely(grows & PROT_GROWSDOWN)) { 385 if (vma->vm_start >= end) 386 goto out; 387 start = vma->vm_start; 388 error = -EINVAL; 389 if (!(vma->vm_flags & VM_GROWSDOWN)) 390 goto out; 391 } else { 392 if (vma->vm_start > start) 393 goto out; 394 if (unlikely(grows & PROT_GROWSUP)) { 395 end = vma->vm_end; 396 error = -EINVAL; 397 if (!(vma->vm_flags & VM_GROWSUP)) 398 goto out; 399 } 400 } 401 if (start > vma->vm_start) 402 prev = vma; 403 404 for (nstart = start ; ; ) { 405 unsigned long newflags; 406 407 /* Here we know that vma->vm_start <= nstart < vma->vm_end. */ 408 409 newflags = vm_flags; 410 newflags |= (vma->vm_flags & ~(VM_READ | VM_WRITE | VM_EXEC)); 411 412 /* newflags >> 4 shift VM_MAY% in place of VM_% */ 413 if ((newflags & ~(newflags >> 4)) & (VM_READ | VM_WRITE | VM_EXEC)) { 414 error = -EACCES; 415 goto out; 416 } 417 418 error = security_file_mprotect(vma, reqprot, prot); 419 if (error) 420 goto out; 421 422 tmp = vma->vm_end; 423 if (tmp > end) 424 tmp = end; 425 error = mprotect_fixup(vma, &prev, nstart, tmp, newflags); 426 if (error) 427 goto out; 428 nstart = tmp; 429 430 if (nstart < prev->vm_end) 431 nstart = prev->vm_end; 432 if (nstart >= end) 433 goto out; 434 435 vma = prev->vm_next; 436 if (!vma || vma->vm_start != nstart) { 437 error = -ENOMEM; 438 goto out; 439 } 440 } 441 out: 442 up_write(¤t->mm->mmap_sem); 443 return error; 444 } 445