| 1 | // SPDX-License-Identifier: GPL-2.0-only |
| 2 | /* |
| 3 | * mm/userfaultfd.c |
| 4 | * |
| 5 | * Copyright (C) 2015 Red Hat, Inc. |
| 6 | */ |
| 7 | |
| 8 | #include <linux/mm.h> |
| 9 | #include <linux/sched/signal.h> |
| 10 | #include <linux/pagemap.h> |
| 11 | #include <linux/rmap.h> |
| 12 | #include <linux/swap.h> |
| 13 | #include <linux/swapops.h> |
| 14 | #include <linux/userfaultfd_k.h> |
| 15 | #include <linux/mmu_notifier.h> |
| 16 | #include <linux/hugetlb.h> |
| 17 | #include <linux/shmem_fs.h> |
| 18 | #include <asm/tlbflush.h> |
| 19 | #include <asm/tlb.h> |
| 20 | #include "internal.h" |
| 21 | |
| 22 | static __always_inline |
| 23 | struct vm_area_struct *find_dst_vma(struct mm_struct *dst_mm, |
| 24 | unsigned long dst_start, |
| 25 | unsigned long len) |
| 26 | { |
| 27 | /* |
| 28 | * Make sure that the dst range is both valid and fully within a |
| 29 | * single existing vma. |
| 30 | */ |
| 31 | struct vm_area_struct *dst_vma; |
| 32 | |
| 33 | dst_vma = find_vma(dst_mm, dst_start); |
| 34 | if (!dst_vma) |
| 35 | return NULL; |
| 36 | |
| 37 | if (dst_start < dst_vma->vm_start || |
| 38 | dst_start + len > dst_vma->vm_end) |
| 39 | return NULL; |
| 40 | |
| 41 | /* |
| 42 | * Check the vma is registered in uffd, this is required to |
| 43 | * enforce the VM_MAYWRITE check done at uffd registration |
| 44 | * time. |
| 45 | */ |
| 46 | if (!dst_vma->vm_userfaultfd_ctx.ctx) |
| 47 | return NULL; |
| 48 | |
| 49 | return dst_vma; |
| 50 | } |
| 51 | |
| 52 | /* |
| 53 | * Install PTEs, to map dst_addr (within dst_vma) to page. |
| 54 | * |
| 55 | * This function handles both MCOPY_ATOMIC_NORMAL and _CONTINUE for both shmem |
| 56 | * and anon, and for both shared and private VMAs. |
| 57 | */ |
| 58 | int mfill_atomic_install_pte(struct mm_struct *dst_mm, pmd_t *dst_pmd, |
| 59 | struct vm_area_struct *dst_vma, |
| 60 | unsigned long dst_addr, struct page *page, |
| 61 | bool newly_allocated, bool wp_copy) |
| 62 | { |
| 63 | int ret; |
| 64 | pte_t _dst_pte, *dst_pte; |
| 65 | bool writable = dst_vma->vm_flags & VM_WRITE; |
| 66 | bool vm_shared = dst_vma->vm_flags & VM_SHARED; |
| 67 | bool page_in_cache = page->mapping; |
| 68 | spinlock_t *ptl; |
| 69 | struct inode *inode; |
| 70 | pgoff_t offset, max_off; |
| 71 | |
| 72 | _dst_pte = mk_pte(page, dst_vma->vm_page_prot); |
| 73 | _dst_pte = pte_mkdirty(_dst_pte); |
| 74 | if (page_in_cache && !vm_shared) |
| 75 | writable = false; |
| 76 | |
| 77 | /* |
| 78 | * Always mark a PTE as write-protected when needed, regardless of |
| 79 | * VM_WRITE, which the user might change. |
| 80 | */ |
| 81 | if (wp_copy) { |
| 82 | _dst_pte = pte_mkuffd_wp(_dst_pte); |
| 83 | writable = false; |
| 84 | } |
| 85 | |
| 86 | if (writable) |
| 87 | _dst_pte = pte_mkwrite(_dst_pte); |
| 88 | else |
| 89 | /* |
| 90 | * We need this to make sure write bit removed; as mk_pte() |
| 91 | * could return a pte with write bit set. |
| 92 | */ |
| 93 | _dst_pte = pte_wrprotect(_dst_pte); |
| 94 | |
| 95 | dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl); |
| 96 | |
| 97 | if (vma_is_shmem(dst_vma)) { |
| 98 | /* serialize against truncate with the page table lock */ |
| 99 | inode = dst_vma->vm_file->f_inode; |
| 100 | offset = linear_page_index(dst_vma, dst_addr); |
| 101 | max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE); |
| 102 | ret = -EFAULT; |
| 103 | if (unlikely(offset >= max_off)) |
| 104 | goto out_unlock; |
| 105 | } |
| 106 | |
| 107 | ret = -EEXIST; |
| 108 | /* |
| 109 | * We allow to overwrite a pte marker: consider when both MISSING|WP |
| 110 | * registered, we firstly wr-protect a none pte which has no page cache |
| 111 | * page backing it, then access the page. |
| 112 | */ |
| 113 | if (!pte_none_mostly(*dst_pte)) |
| 114 | goto out_unlock; |
| 115 | |
| 116 | if (page_in_cache) { |
| 117 | /* Usually, cache pages are already added to LRU */ |
| 118 | if (newly_allocated) |
| 119 | lru_cache_add(page); |
| 120 | page_add_file_rmap(page, dst_vma, false); |
| 121 | } else { |
| 122 | page_add_new_anon_rmap(page, dst_vma, dst_addr); |
| 123 | lru_cache_add_inactive_or_unevictable(page, dst_vma); |
| 124 | } |
| 125 | |
| 126 | /* |
| 127 | * Must happen after rmap, as mm_counter() checks mapping (via |
| 128 | * PageAnon()), which is set by __page_set_anon_rmap(). |
| 129 | */ |
| 130 | inc_mm_counter(dst_mm, mm_counter(page)); |
| 131 | |
| 132 | set_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte); |
| 133 | |
| 134 | /* No need to invalidate - it was non-present before */ |
| 135 | update_mmu_cache(dst_vma, dst_addr, dst_pte); |
| 136 | ret = 0; |
| 137 | out_unlock: |
| 138 | pte_unmap_unlock(dst_pte, ptl); |
| 139 | return ret; |
| 140 | } |
| 141 | |
| 142 | static int mcopy_atomic_pte(struct mm_struct *dst_mm, |
| 143 | pmd_t *dst_pmd, |
| 144 | struct vm_area_struct *dst_vma, |
| 145 | unsigned long dst_addr, |
| 146 | unsigned long src_addr, |
| 147 | struct page **pagep, |
| 148 | bool wp_copy) |
| 149 | { |
| 150 | void *page_kaddr; |
| 151 | int ret; |
| 152 | struct page *page; |
| 153 | |
| 154 | if (!*pagep) { |
| 155 | ret = -ENOMEM; |
| 156 | page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, dst_vma, dst_addr); |
| 157 | if (!page) |
| 158 | goto out; |
| 159 | |
| 160 | page_kaddr = kmap_atomic(page); |
| 161 | ret = copy_from_user(page_kaddr, |
| 162 | (const void __user *) src_addr, |
| 163 | PAGE_SIZE); |
| 164 | kunmap_atomic(page_kaddr); |
| 165 | |
| 166 | /* fallback to copy_from_user outside mmap_lock */ |
| 167 | if (unlikely(ret)) { |
| 168 | ret = -ENOENT; |
| 169 | *pagep = page; |
| 170 | /* don't free the page */ |
| 171 | goto out; |
| 172 | } |
| 173 | |
| 174 | flush_dcache_page(page); |
| 175 | } else { |
| 176 | page = *pagep; |
| 177 | *pagep = NULL; |
| 178 | } |
| 179 | |
| 180 | /* |
| 181 | * The memory barrier inside __SetPageUptodate makes sure that |
| 182 | * preceding stores to the page contents become visible before |
| 183 | * the set_pte_at() write. |
| 184 | */ |
| 185 | __SetPageUptodate(page); |
| 186 | |
| 187 | ret = -ENOMEM; |
| 188 | if (mem_cgroup_charge(page_folio(page), dst_mm, GFP_KERNEL)) |
| 189 | goto out_release; |
| 190 | |
| 191 | ret = mfill_atomic_install_pte(dst_mm, dst_pmd, dst_vma, dst_addr, |
| 192 | page, true, wp_copy); |
| 193 | if (ret) |
| 194 | goto out_release; |
| 195 | out: |
| 196 | return ret; |
| 197 | out_release: |
| 198 | put_page(page); |
| 199 | goto out; |
| 200 | } |
| 201 | |
| 202 | static int mfill_zeropage_pte(struct mm_struct *dst_mm, |
| 203 | pmd_t *dst_pmd, |
| 204 | struct vm_area_struct *dst_vma, |
| 205 | unsigned long dst_addr) |
| 206 | { |
| 207 | pte_t _dst_pte, *dst_pte; |
| 208 | spinlock_t *ptl; |
| 209 | int ret; |
| 210 | pgoff_t offset, max_off; |
| 211 | struct inode *inode; |
| 212 | |
| 213 | _dst_pte = pte_mkspecial(pfn_pte(my_zero_pfn(dst_addr), |
| 214 | dst_vma->vm_page_prot)); |
| 215 | dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl); |
| 216 | if (dst_vma->vm_file) { |
| 217 | /* the shmem MAP_PRIVATE case requires checking the i_size */ |
| 218 | inode = dst_vma->vm_file->f_inode; |
| 219 | offset = linear_page_index(dst_vma, dst_addr); |
| 220 | max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE); |
| 221 | ret = -EFAULT; |
| 222 | if (unlikely(offset >= max_off)) |
| 223 | goto out_unlock; |
| 224 | } |
| 225 | ret = -EEXIST; |
| 226 | if (!pte_none(*dst_pte)) |
| 227 | goto out_unlock; |
| 228 | set_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte); |
| 229 | /* No need to invalidate - it was non-present before */ |
| 230 | update_mmu_cache(dst_vma, dst_addr, dst_pte); |
| 231 | ret = 0; |
| 232 | out_unlock: |
| 233 | pte_unmap_unlock(dst_pte, ptl); |
| 234 | return ret; |
| 235 | } |
| 236 | |
| 237 | /* Handles UFFDIO_CONTINUE for all shmem VMAs (shared or private). */ |
| 238 | static int mcontinue_atomic_pte(struct mm_struct *dst_mm, |
| 239 | pmd_t *dst_pmd, |
| 240 | struct vm_area_struct *dst_vma, |
| 241 | unsigned long dst_addr, |
| 242 | bool wp_copy) |
| 243 | { |
| 244 | struct inode *inode = file_inode(dst_vma->vm_file); |
| 245 | pgoff_t pgoff = linear_page_index(dst_vma, dst_addr); |
| 246 | struct folio *folio; |
| 247 | struct page *page; |
| 248 | int ret; |
| 249 | |
| 250 | ret = shmem_get_folio(inode, pgoff, &folio, SGP_NOALLOC); |
| 251 | /* Our caller expects us to return -EFAULT if we failed to find folio */ |
| 252 | if (ret == -ENOENT) |
| 253 | ret = -EFAULT; |
| 254 | if (ret) |
| 255 | goto out; |
| 256 | if (!folio) { |
| 257 | ret = -EFAULT; |
| 258 | goto out; |
| 259 | } |
| 260 | |
| 261 | page = folio_file_page(folio, pgoff); |
| 262 | if (PageHWPoison(page)) { |
| 263 | ret = -EIO; |
| 264 | goto out_release; |
| 265 | } |
| 266 | |
| 267 | ret = mfill_atomic_install_pte(dst_mm, dst_pmd, dst_vma, dst_addr, |
| 268 | page, false, wp_copy); |
| 269 | if (ret) |
| 270 | goto out_release; |
| 271 | |
| 272 | folio_unlock(folio); |
| 273 | ret = 0; |
| 274 | out: |
| 275 | return ret; |
| 276 | out_release: |
| 277 | folio_unlock(folio); |
| 278 | folio_put(folio); |
| 279 | goto out; |
| 280 | } |
| 281 | |
| 282 | static pmd_t *mm_alloc_pmd(struct mm_struct *mm, unsigned long address) |
| 283 | { |
| 284 | pgd_t *pgd; |
| 285 | p4d_t *p4d; |
| 286 | pud_t *pud; |
| 287 | |
| 288 | pgd = pgd_offset(mm, address); |
| 289 | p4d = p4d_alloc(mm, pgd, address); |
| 290 | if (!p4d) |
| 291 | return NULL; |
| 292 | pud = pud_alloc(mm, p4d, address); |
| 293 | if (!pud) |
| 294 | return NULL; |
| 295 | /* |
| 296 | * Note that we didn't run this because the pmd was |
| 297 | * missing, the *pmd may be already established and in |
| 298 | * turn it may also be a trans_huge_pmd. |
| 299 | */ |
| 300 | return pmd_alloc(mm, pud, address); |
| 301 | } |
| 302 | |
| 303 | #ifdef CONFIG_HUGETLB_PAGE |
| 304 | /* |
| 305 | * __mcopy_atomic processing for HUGETLB vmas. Note that this routine is |
| 306 | * called with mmap_lock held, it will release mmap_lock before returning. |
| 307 | */ |
| 308 | static __always_inline ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm, |
| 309 | struct vm_area_struct *dst_vma, |
| 310 | unsigned long dst_start, |
| 311 | unsigned long src_start, |
| 312 | unsigned long len, |
| 313 | enum mcopy_atomic_mode mode, |
| 314 | bool wp_copy) |
| 315 | { |
| 316 | int vm_shared = dst_vma->vm_flags & VM_SHARED; |
| 317 | ssize_t err; |
| 318 | pte_t *dst_pte; |
| 319 | unsigned long src_addr, dst_addr; |
| 320 | long copied; |
| 321 | struct page *page; |
| 322 | unsigned long vma_hpagesize; |
| 323 | pgoff_t idx; |
| 324 | u32 hash; |
| 325 | struct address_space *mapping; |
| 326 | |
| 327 | /* |
| 328 | * There is no default zero huge page for all huge page sizes as |
| 329 | * supported by hugetlb. A PMD_SIZE huge pages may exist as used |
| 330 | * by THP. Since we can not reliably insert a zero page, this |
| 331 | * feature is not supported. |
| 332 | */ |
| 333 | if (mode == MCOPY_ATOMIC_ZEROPAGE) { |
| 334 | mmap_read_unlock(dst_mm); |
| 335 | return -EINVAL; |
| 336 | } |
| 337 | |
| 338 | src_addr = src_start; |
| 339 | dst_addr = dst_start; |
| 340 | copied = 0; |
| 341 | page = NULL; |
| 342 | vma_hpagesize = vma_kernel_pagesize(dst_vma); |
| 343 | |
| 344 | /* |
| 345 | * Validate alignment based on huge page size |
| 346 | */ |
| 347 | err = -EINVAL; |
| 348 | if (dst_start & (vma_hpagesize - 1) || len & (vma_hpagesize - 1)) |
| 349 | goto out_unlock; |
| 350 | |
| 351 | retry: |
| 352 | /* |
| 353 | * On routine entry dst_vma is set. If we had to drop mmap_lock and |
| 354 | * retry, dst_vma will be set to NULL and we must lookup again. |
| 355 | */ |
| 356 | if (!dst_vma) { |
| 357 | err = -ENOENT; |
| 358 | dst_vma = find_dst_vma(dst_mm, dst_start, len); |
| 359 | if (!dst_vma || !is_vm_hugetlb_page(dst_vma)) |
| 360 | goto out_unlock; |
| 361 | |
| 362 | err = -EINVAL; |
| 363 | if (vma_hpagesize != vma_kernel_pagesize(dst_vma)) |
| 364 | goto out_unlock; |
| 365 | |
| 366 | vm_shared = dst_vma->vm_flags & VM_SHARED; |
| 367 | } |
| 368 | |
| 369 | /* |
| 370 | * If not shared, ensure the dst_vma has a anon_vma. |
| 371 | */ |
| 372 | err = -ENOMEM; |
| 373 | if (!vm_shared) { |
| 374 | if (unlikely(anon_vma_prepare(dst_vma))) |
| 375 | goto out_unlock; |
| 376 | } |
| 377 | |
| 378 | while (src_addr < src_start + len) { |
| 379 | BUG_ON(dst_addr >= dst_start + len); |
| 380 | |
| 381 | /* |
| 382 | * Serialize via vma_lock and hugetlb_fault_mutex. |
| 383 | * vma_lock ensures the dst_pte remains valid even |
| 384 | * in the case of shared pmds. fault mutex prevents |
| 385 | * races with other faulting threads. |
| 386 | */ |
| 387 | idx = linear_page_index(dst_vma, dst_addr); |
| 388 | mapping = dst_vma->vm_file->f_mapping; |
| 389 | hash = hugetlb_fault_mutex_hash(mapping, idx); |
| 390 | mutex_lock(&hugetlb_fault_mutex_table[hash]); |
| 391 | hugetlb_vma_lock_read(dst_vma); |
| 392 | |
| 393 | err = -ENOMEM; |
| 394 | dst_pte = huge_pte_alloc(dst_mm, dst_vma, dst_addr, vma_hpagesize); |
| 395 | if (!dst_pte) { |
| 396 | hugetlb_vma_unlock_read(dst_vma); |
| 397 | mutex_unlock(&hugetlb_fault_mutex_table[hash]); |
| 398 | goto out_unlock; |
| 399 | } |
| 400 | |
| 401 | if (mode != MCOPY_ATOMIC_CONTINUE && |
| 402 | !huge_pte_none_mostly(huge_ptep_get(dst_pte))) { |
| 403 | err = -EEXIST; |
| 404 | hugetlb_vma_unlock_read(dst_vma); |
| 405 | mutex_unlock(&hugetlb_fault_mutex_table[hash]); |
| 406 | goto out_unlock; |
| 407 | } |
| 408 | |
| 409 | err = hugetlb_mcopy_atomic_pte(dst_mm, dst_pte, dst_vma, |
| 410 | dst_addr, src_addr, mode, &page, |
| 411 | wp_copy); |
| 412 | |
| 413 | hugetlb_vma_unlock_read(dst_vma); |
| 414 | mutex_unlock(&hugetlb_fault_mutex_table[hash]); |
| 415 | |
| 416 | cond_resched(); |
| 417 | |
| 418 | if (unlikely(err == -ENOENT)) { |
| 419 | mmap_read_unlock(dst_mm); |
| 420 | BUG_ON(!page); |
| 421 | |
| 422 | err = copy_huge_page_from_user(page, |
| 423 | (const void __user *)src_addr, |
| 424 | vma_hpagesize / PAGE_SIZE, |
| 425 | true); |
| 426 | if (unlikely(err)) { |
| 427 | err = -EFAULT; |
| 428 | goto out; |
| 429 | } |
| 430 | mmap_read_lock(dst_mm); |
| 431 | |
| 432 | dst_vma = NULL; |
| 433 | goto retry; |
| 434 | } else |
| 435 | BUG_ON(page); |
| 436 | |
| 437 | if (!err) { |
| 438 | dst_addr += vma_hpagesize; |
| 439 | src_addr += vma_hpagesize; |
| 440 | copied += vma_hpagesize; |
| 441 | |
| 442 | if (fatal_signal_pending(current)) |
| 443 | err = -EINTR; |
| 444 | } |
| 445 | if (err) |
| 446 | break; |
| 447 | } |
| 448 | |
| 449 | out_unlock: |
| 450 | mmap_read_unlock(dst_mm); |
| 451 | out: |
| 452 | if (page) |
| 453 | put_page(page); |
| 454 | BUG_ON(copied < 0); |
| 455 | BUG_ON(err > 0); |
| 456 | BUG_ON(!copied && !err); |
| 457 | return copied ? copied : err; |
| 458 | } |
| 459 | #else /* !CONFIG_HUGETLB_PAGE */ |
| 460 | /* fail at build time if gcc attempts to use this */ |
| 461 | extern ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm, |
| 462 | struct vm_area_struct *dst_vma, |
| 463 | unsigned long dst_start, |
| 464 | unsigned long src_start, |
| 465 | unsigned long len, |
| 466 | enum mcopy_atomic_mode mode, |
| 467 | bool wp_copy); |
| 468 | #endif /* CONFIG_HUGETLB_PAGE */ |
| 469 | |
| 470 | static __always_inline ssize_t mfill_atomic_pte(struct mm_struct *dst_mm, |
| 471 | pmd_t *dst_pmd, |
| 472 | struct vm_area_struct *dst_vma, |
| 473 | unsigned long dst_addr, |
| 474 | unsigned long src_addr, |
| 475 | struct page **page, |
| 476 | enum mcopy_atomic_mode mode, |
| 477 | bool wp_copy) |
| 478 | { |
| 479 | ssize_t err; |
| 480 | |
| 481 | if (mode == MCOPY_ATOMIC_CONTINUE) { |
| 482 | return mcontinue_atomic_pte(dst_mm, dst_pmd, dst_vma, dst_addr, |
| 483 | wp_copy); |
| 484 | } |
| 485 | |
| 486 | /* |
| 487 | * The normal page fault path for a shmem will invoke the |
| 488 | * fault, fill the hole in the file and COW it right away. The |
| 489 | * result generates plain anonymous memory. So when we are |
| 490 | * asked to fill an hole in a MAP_PRIVATE shmem mapping, we'll |
| 491 | * generate anonymous memory directly without actually filling |
| 492 | * the hole. For the MAP_PRIVATE case the robustness check |
| 493 | * only happens in the pagetable (to verify it's still none) |
| 494 | * and not in the radix tree. |
| 495 | */ |
| 496 | if (!(dst_vma->vm_flags & VM_SHARED)) { |
| 497 | if (mode == MCOPY_ATOMIC_NORMAL) |
| 498 | err = mcopy_atomic_pte(dst_mm, dst_pmd, dst_vma, |
| 499 | dst_addr, src_addr, page, |
| 500 | wp_copy); |
| 501 | else |
| 502 | err = mfill_zeropage_pte(dst_mm, dst_pmd, |
| 503 | dst_vma, dst_addr); |
| 504 | } else { |
| 505 | err = shmem_mfill_atomic_pte(dst_mm, dst_pmd, dst_vma, |
| 506 | dst_addr, src_addr, |
| 507 | mode != MCOPY_ATOMIC_NORMAL, |
| 508 | wp_copy, page); |
| 509 | } |
| 510 | |
| 511 | return err; |
| 512 | } |
| 513 | |
| 514 | static __always_inline ssize_t __mcopy_atomic(struct mm_struct *dst_mm, |
| 515 | unsigned long dst_start, |
| 516 | unsigned long src_start, |
| 517 | unsigned long len, |
| 518 | enum mcopy_atomic_mode mcopy_mode, |
| 519 | atomic_t *mmap_changing, |
| 520 | __u64 mode) |
| 521 | { |
| 522 | struct vm_area_struct *dst_vma; |
| 523 | ssize_t err; |
| 524 | pmd_t *dst_pmd; |
| 525 | unsigned long src_addr, dst_addr; |
| 526 | long copied; |
| 527 | struct page *page; |
| 528 | bool wp_copy; |
| 529 | |
| 530 | /* |
| 531 | * Sanitize the command parameters: |
| 532 | */ |
| 533 | BUG_ON(dst_start & ~PAGE_MASK); |
| 534 | BUG_ON(len & ~PAGE_MASK); |
| 535 | |
| 536 | /* Does the address range wrap, or is the span zero-sized? */ |
| 537 | BUG_ON(src_start + len <= src_start); |
| 538 | BUG_ON(dst_start + len <= dst_start); |
| 539 | |
| 540 | src_addr = src_start; |
| 541 | dst_addr = dst_start; |
| 542 | copied = 0; |
| 543 | page = NULL; |
| 544 | retry: |
| 545 | mmap_read_lock(dst_mm); |
| 546 | |
| 547 | /* |
| 548 | * If memory mappings are changing because of non-cooperative |
| 549 | * operation (e.g. mremap) running in parallel, bail out and |
| 550 | * request the user to retry later |
| 551 | */ |
| 552 | err = -EAGAIN; |
| 553 | if (mmap_changing && atomic_read(mmap_changing)) |
| 554 | goto out_unlock; |
| 555 | |
| 556 | /* |
| 557 | * Make sure the vma is not shared, that the dst range is |
| 558 | * both valid and fully within a single existing vma. |
| 559 | */ |
| 560 | err = -ENOENT; |
| 561 | dst_vma = find_dst_vma(dst_mm, dst_start, len); |
| 562 | if (!dst_vma) |
| 563 | goto out_unlock; |
| 564 | |
| 565 | err = -EINVAL; |
| 566 | /* |
| 567 | * shmem_zero_setup is invoked in mmap for MAP_ANONYMOUS|MAP_SHARED but |
| 568 | * it will overwrite vm_ops, so vma_is_anonymous must return false. |
| 569 | */ |
| 570 | if (WARN_ON_ONCE(vma_is_anonymous(dst_vma) && |
| 571 | dst_vma->vm_flags & VM_SHARED)) |
| 572 | goto out_unlock; |
| 573 | |
| 574 | /* |
| 575 | * validate 'mode' now that we know the dst_vma: don't allow |
| 576 | * a wrprotect copy if the userfaultfd didn't register as WP. |
| 577 | */ |
| 578 | wp_copy = mode & UFFDIO_COPY_MODE_WP; |
| 579 | if (wp_copy && !(dst_vma->vm_flags & VM_UFFD_WP)) |
| 580 | goto out_unlock; |
| 581 | |
| 582 | /* |
| 583 | * If this is a HUGETLB vma, pass off to appropriate routine |
| 584 | */ |
| 585 | if (is_vm_hugetlb_page(dst_vma)) |
| 586 | return __mcopy_atomic_hugetlb(dst_mm, dst_vma, dst_start, |
| 587 | src_start, len, mcopy_mode, |
| 588 | wp_copy); |
| 589 | |
| 590 | if (!vma_is_anonymous(dst_vma) && !vma_is_shmem(dst_vma)) |
| 591 | goto out_unlock; |
| 592 | if (!vma_is_shmem(dst_vma) && mcopy_mode == MCOPY_ATOMIC_CONTINUE) |
| 593 | goto out_unlock; |
| 594 | |
| 595 | /* |
| 596 | * Ensure the dst_vma has a anon_vma or this page |
| 597 | * would get a NULL anon_vma when moved in the |
| 598 | * dst_vma. |
| 599 | */ |
| 600 | err = -ENOMEM; |
| 601 | if (!(dst_vma->vm_flags & VM_SHARED) && |
| 602 | unlikely(anon_vma_prepare(dst_vma))) |
| 603 | goto out_unlock; |
| 604 | |
| 605 | while (src_addr < src_start + len) { |
| 606 | pmd_t dst_pmdval; |
| 607 | |
| 608 | BUG_ON(dst_addr >= dst_start + len); |
| 609 | |
| 610 | dst_pmd = mm_alloc_pmd(dst_mm, dst_addr); |
| 611 | if (unlikely(!dst_pmd)) { |
| 612 | err = -ENOMEM; |
| 613 | break; |
| 614 | } |
| 615 | |
| 616 | dst_pmdval = pmd_read_atomic(dst_pmd); |
| 617 | /* |
| 618 | * If the dst_pmd is mapped as THP don't |
| 619 | * override it and just be strict. |
| 620 | */ |
| 621 | if (unlikely(pmd_trans_huge(dst_pmdval))) { |
| 622 | err = -EEXIST; |
| 623 | break; |
| 624 | } |
| 625 | if (unlikely(pmd_none(dst_pmdval)) && |
| 626 | unlikely(__pte_alloc(dst_mm, dst_pmd))) { |
| 627 | err = -ENOMEM; |
| 628 | break; |
| 629 | } |
| 630 | /* If an huge pmd materialized from under us fail */ |
| 631 | if (unlikely(pmd_trans_huge(*dst_pmd))) { |
| 632 | err = -EFAULT; |
| 633 | break; |
| 634 | } |
| 635 | |
| 636 | BUG_ON(pmd_none(*dst_pmd)); |
| 637 | BUG_ON(pmd_trans_huge(*dst_pmd)); |
| 638 | |
| 639 | err = mfill_atomic_pte(dst_mm, dst_pmd, dst_vma, dst_addr, |
| 640 | src_addr, &page, mcopy_mode, wp_copy); |
| 641 | cond_resched(); |
| 642 | |
| 643 | if (unlikely(err == -ENOENT)) { |
| 644 | void *page_kaddr; |
| 645 | |
| 646 | mmap_read_unlock(dst_mm); |
| 647 | BUG_ON(!page); |
| 648 | |
| 649 | page_kaddr = kmap(page); |
| 650 | err = copy_from_user(page_kaddr, |
| 651 | (const void __user *) src_addr, |
| 652 | PAGE_SIZE); |
| 653 | kunmap(page); |
| 654 | if (unlikely(err)) { |
| 655 | err = -EFAULT; |
| 656 | goto out; |
| 657 | } |
| 658 | flush_dcache_page(page); |
| 659 | goto retry; |
| 660 | } else |
| 661 | BUG_ON(page); |
| 662 | |
| 663 | if (!err) { |
| 664 | dst_addr += PAGE_SIZE; |
| 665 | src_addr += PAGE_SIZE; |
| 666 | copied += PAGE_SIZE; |
| 667 | |
| 668 | if (fatal_signal_pending(current)) |
| 669 | err = -EINTR; |
| 670 | } |
| 671 | if (err) |
| 672 | break; |
| 673 | } |
| 674 | |
| 675 | out_unlock: |
| 676 | mmap_read_unlock(dst_mm); |
| 677 | out: |
| 678 | if (page) |
| 679 | put_page(page); |
| 680 | BUG_ON(copied < 0); |
| 681 | BUG_ON(err > 0); |
| 682 | BUG_ON(!copied && !err); |
| 683 | return copied ? copied : err; |
| 684 | } |
| 685 | |
| 686 | ssize_t mcopy_atomic(struct mm_struct *dst_mm, unsigned long dst_start, |
| 687 | unsigned long src_start, unsigned long len, |
| 688 | atomic_t *mmap_changing, __u64 mode) |
| 689 | { |
| 690 | return __mcopy_atomic(dst_mm, dst_start, src_start, len, |
| 691 | MCOPY_ATOMIC_NORMAL, mmap_changing, mode); |
| 692 | } |
| 693 | |
| 694 | ssize_t mfill_zeropage(struct mm_struct *dst_mm, unsigned long start, |
| 695 | unsigned long len, atomic_t *mmap_changing) |
| 696 | { |
| 697 | return __mcopy_atomic(dst_mm, start, 0, len, MCOPY_ATOMIC_ZEROPAGE, |
| 698 | mmap_changing, 0); |
| 699 | } |
| 700 | |
| 701 | ssize_t mcopy_continue(struct mm_struct *dst_mm, unsigned long start, |
| 702 | unsigned long len, atomic_t *mmap_changing) |
| 703 | { |
| 704 | return __mcopy_atomic(dst_mm, start, 0, len, MCOPY_ATOMIC_CONTINUE, |
| 705 | mmap_changing, 0); |
| 706 | } |
| 707 | |
| 708 | void uffd_wp_range(struct mm_struct *dst_mm, struct vm_area_struct *dst_vma, |
| 709 | unsigned long start, unsigned long len, bool enable_wp) |
| 710 | { |
| 711 | struct mmu_gather tlb; |
| 712 | pgprot_t newprot; |
| 713 | |
| 714 | if (enable_wp) |
| 715 | newprot = vm_get_page_prot(dst_vma->vm_flags & ~(VM_WRITE)); |
| 716 | else |
| 717 | newprot = vm_get_page_prot(dst_vma->vm_flags); |
| 718 | |
| 719 | tlb_gather_mmu(&tlb, dst_mm); |
| 720 | change_protection(&tlb, dst_vma, start, start + len, newprot, |
| 721 | enable_wp ? MM_CP_UFFD_WP : MM_CP_UFFD_WP_RESOLVE); |
| 722 | tlb_finish_mmu(&tlb); |
| 723 | } |
| 724 | |
| 725 | int mwriteprotect_range(struct mm_struct *dst_mm, unsigned long start, |
| 726 | unsigned long len, bool enable_wp, |
| 727 | atomic_t *mmap_changing) |
| 728 | { |
| 729 | struct vm_area_struct *dst_vma; |
| 730 | unsigned long page_mask; |
| 731 | int err; |
| 732 | |
| 733 | /* |
| 734 | * Sanitize the command parameters: |
| 735 | */ |
| 736 | BUG_ON(start & ~PAGE_MASK); |
| 737 | BUG_ON(len & ~PAGE_MASK); |
| 738 | |
| 739 | /* Does the address range wrap, or is the span zero-sized? */ |
| 740 | BUG_ON(start + len <= start); |
| 741 | |
| 742 | mmap_read_lock(dst_mm); |
| 743 | |
| 744 | /* |
| 745 | * If memory mappings are changing because of non-cooperative |
| 746 | * operation (e.g. mremap) running in parallel, bail out and |
| 747 | * request the user to retry later |
| 748 | */ |
| 749 | err = -EAGAIN; |
| 750 | if (mmap_changing && atomic_read(mmap_changing)) |
| 751 | goto out_unlock; |
| 752 | |
| 753 | err = -ENOENT; |
| 754 | dst_vma = find_dst_vma(dst_mm, start, len); |
| 755 | |
| 756 | if (!dst_vma) |
| 757 | goto out_unlock; |
| 758 | if (!userfaultfd_wp(dst_vma)) |
| 759 | goto out_unlock; |
| 760 | if (!vma_can_userfault(dst_vma, dst_vma->vm_flags)) |
| 761 | goto out_unlock; |
| 762 | |
| 763 | if (is_vm_hugetlb_page(dst_vma)) { |
| 764 | err = -EINVAL; |
| 765 | page_mask = vma_kernel_pagesize(dst_vma) - 1; |
| 766 | if ((start & page_mask) || (len & page_mask)) |
| 767 | goto out_unlock; |
| 768 | } |
| 769 | |
| 770 | uffd_wp_range(dst_mm, dst_vma, start, len, enable_wp); |
| 771 | |
| 772 | err = 0; |
| 773 | out_unlock: |
| 774 | mmap_read_unlock(dst_mm); |
| 775 | return err; |
| 776 | } |