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