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 79 /* 80 * Avoid trapping faults against the zero or KSM 81 * pages. See similar comment in change_huge_pmd. 82 */ 83 if (prot_numa) { 84 struct page *page; 85 86 page = vm_normal_page(vma, addr, oldpte); 87 if (!page || PageKsm(page)) 88 continue; 89 90 /* Avoid TLB flush if possible */ 91 if (pte_protnone(oldpte)) 92 continue; 93 } 94 95 ptent = ptep_modify_prot_start(mm, addr, pte); 96 ptent = pte_modify(ptent, newprot); 97 98 /* Avoid taking write faults for known dirty pages */ 99 if (dirty_accountable && pte_dirty(ptent) && 100 (pte_soft_dirty(ptent) || 101 !(vma->vm_flags & VM_SOFTDIRTY))) { 102 ptent = pte_mkwrite(ptent); 103 } 104 ptep_modify_prot_commit(mm, addr, pte, ptent); 105 pages++; 106 } else if (IS_ENABLED(CONFIG_MIGRATION)) { 107 swp_entry_t entry = pte_to_swp_entry(oldpte); 108 109 if (is_write_migration_entry(entry)) { 110 pte_t newpte; 111 /* 112 * A protection check is difficult so 113 * just be safe and disable write 114 */ 115 make_migration_entry_read(&entry); 116 newpte = swp_entry_to_pte(entry); 117 if (pte_swp_soft_dirty(oldpte)) 118 newpte = pte_swp_mksoft_dirty(newpte); 119 set_pte_at(mm, addr, pte, newpte); 120 121 pages++; 122 } 123 } 124 } while (pte++, addr += PAGE_SIZE, addr != end); 125 arch_leave_lazy_mmu_mode(); 126 pte_unmap_unlock(pte - 1, ptl); 127 128 return pages; 129 } 130 131 static inline unsigned long change_pmd_range(struct vm_area_struct *vma, 132 pud_t *pud, unsigned long addr, unsigned long end, 133 pgprot_t newprot, int dirty_accountable, int prot_numa) 134 { 135 pmd_t *pmd; 136 struct mm_struct *mm = vma->vm_mm; 137 unsigned long next; 138 unsigned long pages = 0; 139 unsigned long nr_huge_updates = 0; 140 unsigned long mni_start = 0; 141 142 pmd = pmd_offset(pud, addr); 143 do { 144 unsigned long this_pages; 145 146 next = pmd_addr_end(addr, end); 147 if (!pmd_trans_huge(*pmd) && pmd_none_or_clear_bad(pmd)) 148 continue; 149 150 /* invoke the mmu notifier if the pmd is populated */ 151 if (!mni_start) { 152 mni_start = addr; 153 mmu_notifier_invalidate_range_start(mm, mni_start, end); 154 } 155 156 if (pmd_trans_huge(*pmd)) { 157 if (next - addr != HPAGE_PMD_SIZE) 158 split_huge_page_pmd(vma, addr, pmd); 159 else { 160 int nr_ptes = change_huge_pmd(vma, pmd, addr, 161 newprot, prot_numa); 162 163 if (nr_ptes) { 164 if (nr_ptes == HPAGE_PMD_NR) { 165 pages += HPAGE_PMD_NR; 166 nr_huge_updates++; 167 } 168 169 /* huge pmd was handled */ 170 continue; 171 } 172 } 173 /* fall through, the trans huge pmd just split */ 174 } 175 this_pages = change_pte_range(vma, pmd, addr, next, newprot, 176 dirty_accountable, prot_numa); 177 pages += this_pages; 178 } while (pmd++, addr = next, addr != end); 179 180 if (mni_start) 181 mmu_notifier_invalidate_range_end(mm, mni_start, end); 182 183 if (nr_huge_updates) 184 count_vm_numa_events(NUMA_HUGE_PTE_UPDATES, nr_huge_updates); 185 return pages; 186 } 187 188 static inline unsigned long change_pud_range(struct vm_area_struct *vma, 189 pgd_t *pgd, unsigned long addr, unsigned long end, 190 pgprot_t newprot, int dirty_accountable, int prot_numa) 191 { 192 pud_t *pud; 193 unsigned long next; 194 unsigned long pages = 0; 195 196 pud = pud_offset(pgd, addr); 197 do { 198 next = pud_addr_end(addr, end); 199 if (pud_none_or_clear_bad(pud)) 200 continue; 201 pages += change_pmd_range(vma, pud, addr, next, newprot, 202 dirty_accountable, prot_numa); 203 } while (pud++, addr = next, addr != end); 204 205 return pages; 206 } 207 208 static unsigned long change_protection_range(struct vm_area_struct *vma, 209 unsigned long addr, unsigned long end, pgprot_t newprot, 210 int dirty_accountable, int prot_numa) 211 { 212 struct mm_struct *mm = vma->vm_mm; 213 pgd_t *pgd; 214 unsigned long next; 215 unsigned long start = addr; 216 unsigned long pages = 0; 217 218 BUG_ON(addr >= end); 219 pgd = pgd_offset(mm, addr); 220 flush_cache_range(vma, addr, end); 221 set_tlb_flush_pending(mm); 222 do { 223 next = pgd_addr_end(addr, end); 224 if (pgd_none_or_clear_bad(pgd)) 225 continue; 226 pages += change_pud_range(vma, pgd, addr, next, newprot, 227 dirty_accountable, prot_numa); 228 } while (pgd++, addr = next, addr != end); 229 230 /* Only flush the TLB if we actually modified any entries: */ 231 if (pages) 232 flush_tlb_range(vma, start, end); 233 clear_tlb_flush_pending(mm); 234 235 return pages; 236 } 237 238 unsigned long change_protection(struct vm_area_struct *vma, unsigned long start, 239 unsigned long end, pgprot_t newprot, 240 int dirty_accountable, int prot_numa) 241 { 242 unsigned long pages; 243 244 if (is_vm_hugetlb_page(vma)) 245 pages = hugetlb_change_protection(vma, start, end, newprot); 246 else 247 pages = change_protection_range(vma, start, end, newprot, dirty_accountable, prot_numa); 248 249 return pages; 250 } 251 252 int 253 mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev, 254 unsigned long start, unsigned long end, unsigned long newflags) 255 { 256 struct mm_struct *mm = vma->vm_mm; 257 unsigned long oldflags = vma->vm_flags; 258 long nrpages = (end - start) >> PAGE_SHIFT; 259 unsigned long charged = 0; 260 pgoff_t pgoff; 261 int error; 262 int dirty_accountable = 0; 263 264 if (newflags == oldflags) { 265 *pprev = vma; 266 return 0; 267 } 268 269 /* 270 * If we make a private mapping writable we increase our commit; 271 * but (without finer accounting) cannot reduce our commit if we 272 * make it unwritable again. hugetlb mapping were accounted for 273 * even if read-only so there is no need to account for them here 274 */ 275 if (newflags & VM_WRITE) { 276 if (!(oldflags & (VM_ACCOUNT|VM_WRITE|VM_HUGETLB| 277 VM_SHARED|VM_NORESERVE))) { 278 charged = nrpages; 279 if (security_vm_enough_memory_mm(mm, charged)) 280 return -ENOMEM; 281 newflags |= VM_ACCOUNT; 282 } 283 } 284 285 /* 286 * First try to merge with previous and/or next vma. 287 */ 288 pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT); 289 *pprev = vma_merge(mm, *pprev, start, end, newflags, 290 vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma)); 291 if (*pprev) { 292 vma = *pprev; 293 goto success; 294 } 295 296 *pprev = vma; 297 298 if (start != vma->vm_start) { 299 error = split_vma(mm, vma, start, 1); 300 if (error) 301 goto fail; 302 } 303 304 if (end != vma->vm_end) { 305 error = split_vma(mm, vma, end, 0); 306 if (error) 307 goto fail; 308 } 309 310 success: 311 /* 312 * vm_flags and vm_page_prot are protected by the mmap_sem 313 * held in write mode. 314 */ 315 vma->vm_flags = newflags; 316 dirty_accountable = vma_wants_writenotify(vma); 317 vma_set_page_prot(vma); 318 319 change_protection(vma, start, end, vma->vm_page_prot, 320 dirty_accountable, 0); 321 322 vm_stat_account(mm, oldflags, vma->vm_file, -nrpages); 323 vm_stat_account(mm, newflags, vma->vm_file, nrpages); 324 perf_event_mmap(vma); 325 return 0; 326 327 fail: 328 vm_unacct_memory(charged); 329 return error; 330 } 331 332 SYSCALL_DEFINE3(mprotect, unsigned long, start, size_t, len, 333 unsigned long, prot) 334 { 335 unsigned long vm_flags, nstart, end, tmp, reqprot; 336 struct vm_area_struct *vma, *prev; 337 int error = -EINVAL; 338 const int grows = prot & (PROT_GROWSDOWN|PROT_GROWSUP); 339 prot &= ~(PROT_GROWSDOWN|PROT_GROWSUP); 340 if (grows == (PROT_GROWSDOWN|PROT_GROWSUP)) /* can't be both */ 341 return -EINVAL; 342 343 if (start & ~PAGE_MASK) 344 return -EINVAL; 345 if (!len) 346 return 0; 347 len = PAGE_ALIGN(len); 348 end = start + len; 349 if (end <= start) 350 return -ENOMEM; 351 if (!arch_validate_prot(prot)) 352 return -EINVAL; 353 354 reqprot = prot; 355 /* 356 * Does the application expect PROT_READ to imply PROT_EXEC: 357 */ 358 if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC)) 359 prot |= PROT_EXEC; 360 361 vm_flags = calc_vm_prot_bits(prot); 362 363 down_write(¤t->mm->mmap_sem); 364 365 vma = find_vma(current->mm, start); 366 error = -ENOMEM; 367 if (!vma) 368 goto out; 369 prev = vma->vm_prev; 370 if (unlikely(grows & PROT_GROWSDOWN)) { 371 if (vma->vm_start >= end) 372 goto out; 373 start = vma->vm_start; 374 error = -EINVAL; 375 if (!(vma->vm_flags & VM_GROWSDOWN)) 376 goto out; 377 } else { 378 if (vma->vm_start > start) 379 goto out; 380 if (unlikely(grows & PROT_GROWSUP)) { 381 end = vma->vm_end; 382 error = -EINVAL; 383 if (!(vma->vm_flags & VM_GROWSUP)) 384 goto out; 385 } 386 } 387 if (start > vma->vm_start) 388 prev = vma; 389 390 for (nstart = start ; ; ) { 391 unsigned long newflags; 392 393 /* Here we know that vma->vm_start <= nstart < vma->vm_end. */ 394 395 newflags = vm_flags; 396 newflags |= (vma->vm_flags & ~(VM_READ | VM_WRITE | VM_EXEC)); 397 398 /* newflags >> 4 shift VM_MAY% in place of VM_% */ 399 if ((newflags & ~(newflags >> 4)) & (VM_READ | VM_WRITE | VM_EXEC)) { 400 error = -EACCES; 401 goto out; 402 } 403 404 error = security_file_mprotect(vma, reqprot, prot); 405 if (error) 406 goto out; 407 408 tmp = vma->vm_end; 409 if (tmp > end) 410 tmp = end; 411 error = mprotect_fixup(vma, &prev, nstart, tmp, newflags); 412 if (error) 413 goto out; 414 nstart = tmp; 415 416 if (nstart < prev->vm_end) 417 nstart = prev->vm_end; 418 if (nstart >= end) 419 goto out; 420 421 vma = prev->vm_next; 422 if (!vma || vma->vm_start != nstart) { 423 error = -ENOMEM; 424 goto out; 425 } 426 } 427 out: 428 up_write(¤t->mm->mmap_sem); 429 return error; 430 } 431