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