| 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 (!range_in_vma(dst_vma, dst_start, dst_start + len)) |
| 35 | return NULL; |
| 36 | |
| 37 | /* |
| 38 | * Check the vma is registered in uffd, this is required to |
| 39 | * enforce the VM_MAYWRITE check done at uffd registration |
| 40 | * time. |
| 41 | */ |
| 42 | if (!dst_vma->vm_userfaultfd_ctx.ctx) |
| 43 | return NULL; |
| 44 | |
| 45 | return dst_vma; |
| 46 | } |
| 47 | |
| 48 | /* Check if dst_addr is outside of file's size. Must be called with ptl held. */ |
| 49 | static bool mfill_file_over_size(struct vm_area_struct *dst_vma, |
| 50 | unsigned long dst_addr) |
| 51 | { |
| 52 | struct inode *inode; |
| 53 | pgoff_t offset, max_off; |
| 54 | |
| 55 | if (!dst_vma->vm_file) |
| 56 | return false; |
| 57 | |
| 58 | inode = dst_vma->vm_file->f_inode; |
| 59 | offset = linear_page_index(dst_vma, dst_addr); |
| 60 | max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE); |
| 61 | return offset >= max_off; |
| 62 | } |
| 63 | |
| 64 | /* |
| 65 | * Install PTEs, to map dst_addr (within dst_vma) to page. |
| 66 | * |
| 67 | * This function handles both MCOPY_ATOMIC_NORMAL and _CONTINUE for both shmem |
| 68 | * and anon, and for both shared and private VMAs. |
| 69 | */ |
| 70 | int mfill_atomic_install_pte(pmd_t *dst_pmd, |
| 71 | struct vm_area_struct *dst_vma, |
| 72 | unsigned long dst_addr, struct page *page, |
| 73 | bool newly_allocated, uffd_flags_t flags) |
| 74 | { |
| 75 | int ret; |
| 76 | struct mm_struct *dst_mm = dst_vma->vm_mm; |
| 77 | pte_t _dst_pte, *dst_pte; |
| 78 | bool writable = dst_vma->vm_flags & VM_WRITE; |
| 79 | bool vm_shared = dst_vma->vm_flags & VM_SHARED; |
| 80 | bool page_in_cache = page_mapping(page); |
| 81 | spinlock_t *ptl; |
| 82 | struct folio *folio; |
| 83 | |
| 84 | _dst_pte = mk_pte(page, dst_vma->vm_page_prot); |
| 85 | _dst_pte = pte_mkdirty(_dst_pte); |
| 86 | if (page_in_cache && !vm_shared) |
| 87 | writable = false; |
| 88 | if (writable) |
| 89 | _dst_pte = pte_mkwrite(_dst_pte, dst_vma); |
| 90 | if (flags & MFILL_ATOMIC_WP) |
| 91 | _dst_pte = pte_mkuffd_wp(_dst_pte); |
| 92 | |
| 93 | ret = -EAGAIN; |
| 94 | dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl); |
| 95 | if (!dst_pte) |
| 96 | goto out; |
| 97 | |
| 98 | if (mfill_file_over_size(dst_vma, dst_addr)) { |
| 99 | ret = -EFAULT; |
| 100 | goto out_unlock; |
| 101 | } |
| 102 | |
| 103 | ret = -EEXIST; |
| 104 | /* |
| 105 | * We allow to overwrite a pte marker: consider when both MISSING|WP |
| 106 | * registered, we firstly wr-protect a none pte which has no page cache |
| 107 | * page backing it, then access the page. |
| 108 | */ |
| 109 | if (!pte_none_mostly(ptep_get(dst_pte))) |
| 110 | goto out_unlock; |
| 111 | |
| 112 | folio = page_folio(page); |
| 113 | if (page_in_cache) { |
| 114 | /* Usually, cache pages are already added to LRU */ |
| 115 | if (newly_allocated) |
| 116 | folio_add_lru(folio); |
| 117 | folio_add_file_rmap_pte(folio, page, dst_vma); |
| 118 | } else { |
| 119 | folio_add_new_anon_rmap(folio, dst_vma, dst_addr); |
| 120 | folio_add_lru_vma(folio, dst_vma); |
| 121 | } |
| 122 | |
| 123 | /* |
| 124 | * Must happen after rmap, as mm_counter() checks mapping (via |
| 125 | * PageAnon()), which is set by __page_set_anon_rmap(). |
| 126 | */ |
| 127 | inc_mm_counter(dst_mm, mm_counter(page)); |
| 128 | |
| 129 | set_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte); |
| 130 | |
| 131 | /* No need to invalidate - it was non-present before */ |
| 132 | update_mmu_cache(dst_vma, dst_addr, dst_pte); |
| 133 | ret = 0; |
| 134 | out_unlock: |
| 135 | pte_unmap_unlock(dst_pte, ptl); |
| 136 | out: |
| 137 | return ret; |
| 138 | } |
| 139 | |
| 140 | static int mfill_atomic_pte_copy(pmd_t *dst_pmd, |
| 141 | struct vm_area_struct *dst_vma, |
| 142 | unsigned long dst_addr, |
| 143 | unsigned long src_addr, |
| 144 | uffd_flags_t flags, |
| 145 | struct folio **foliop) |
| 146 | { |
| 147 | void *kaddr; |
| 148 | int ret; |
| 149 | struct folio *folio; |
| 150 | |
| 151 | if (!*foliop) { |
| 152 | ret = -ENOMEM; |
| 153 | folio = vma_alloc_folio(GFP_HIGHUSER_MOVABLE, 0, dst_vma, |
| 154 | dst_addr, false); |
| 155 | if (!folio) |
| 156 | goto out; |
| 157 | |
| 158 | kaddr = kmap_local_folio(folio, 0); |
| 159 | /* |
| 160 | * The read mmap_lock is held here. Despite the |
| 161 | * mmap_lock being read recursive a deadlock is still |
| 162 | * possible if a writer has taken a lock. For example: |
| 163 | * |
| 164 | * process A thread 1 takes read lock on own mmap_lock |
| 165 | * process A thread 2 calls mmap, blocks taking write lock |
| 166 | * process B thread 1 takes page fault, read lock on own mmap lock |
| 167 | * process B thread 2 calls mmap, blocks taking write lock |
| 168 | * process A thread 1 blocks taking read lock on process B |
| 169 | * process B thread 1 blocks taking read lock on process A |
| 170 | * |
| 171 | * Disable page faults to prevent potential deadlock |
| 172 | * and retry the copy outside the mmap_lock. |
| 173 | */ |
| 174 | pagefault_disable(); |
| 175 | ret = copy_from_user(kaddr, (const void __user *) src_addr, |
| 176 | PAGE_SIZE); |
| 177 | pagefault_enable(); |
| 178 | kunmap_local(kaddr); |
| 179 | |
| 180 | /* fallback to copy_from_user outside mmap_lock */ |
| 181 | if (unlikely(ret)) { |
| 182 | ret = -ENOENT; |
| 183 | *foliop = folio; |
| 184 | /* don't free the page */ |
| 185 | goto out; |
| 186 | } |
| 187 | |
| 188 | flush_dcache_folio(folio); |
| 189 | } else { |
| 190 | folio = *foliop; |
| 191 | *foliop = NULL; |
| 192 | } |
| 193 | |
| 194 | /* |
| 195 | * The memory barrier inside __folio_mark_uptodate makes sure that |
| 196 | * preceding stores to the page contents become visible before |
| 197 | * the set_pte_at() write. |
| 198 | */ |
| 199 | __folio_mark_uptodate(folio); |
| 200 | |
| 201 | ret = -ENOMEM; |
| 202 | if (mem_cgroup_charge(folio, dst_vma->vm_mm, GFP_KERNEL)) |
| 203 | goto out_release; |
| 204 | |
| 205 | ret = mfill_atomic_install_pte(dst_pmd, dst_vma, dst_addr, |
| 206 | &folio->page, true, flags); |
| 207 | if (ret) |
| 208 | goto out_release; |
| 209 | out: |
| 210 | return ret; |
| 211 | out_release: |
| 212 | folio_put(folio); |
| 213 | goto out; |
| 214 | } |
| 215 | |
| 216 | static int mfill_atomic_pte_zeropage(pmd_t *dst_pmd, |
| 217 | struct vm_area_struct *dst_vma, |
| 218 | unsigned long dst_addr) |
| 219 | { |
| 220 | pte_t _dst_pte, *dst_pte; |
| 221 | spinlock_t *ptl; |
| 222 | int ret; |
| 223 | |
| 224 | _dst_pte = pte_mkspecial(pfn_pte(my_zero_pfn(dst_addr), |
| 225 | dst_vma->vm_page_prot)); |
| 226 | ret = -EAGAIN; |
| 227 | dst_pte = pte_offset_map_lock(dst_vma->vm_mm, dst_pmd, dst_addr, &ptl); |
| 228 | if (!dst_pte) |
| 229 | goto out; |
| 230 | if (mfill_file_over_size(dst_vma, dst_addr)) { |
| 231 | ret = -EFAULT; |
| 232 | goto out_unlock; |
| 233 | } |
| 234 | ret = -EEXIST; |
| 235 | if (!pte_none(ptep_get(dst_pte))) |
| 236 | goto out_unlock; |
| 237 | set_pte_at(dst_vma->vm_mm, dst_addr, dst_pte, _dst_pte); |
| 238 | /* No need to invalidate - it was non-present before */ |
| 239 | update_mmu_cache(dst_vma, dst_addr, dst_pte); |
| 240 | ret = 0; |
| 241 | out_unlock: |
| 242 | pte_unmap_unlock(dst_pte, ptl); |
| 243 | out: |
| 244 | return ret; |
| 245 | } |
| 246 | |
| 247 | /* Handles UFFDIO_CONTINUE for all shmem VMAs (shared or private). */ |
| 248 | static int mfill_atomic_pte_continue(pmd_t *dst_pmd, |
| 249 | struct vm_area_struct *dst_vma, |
| 250 | unsigned long dst_addr, |
| 251 | uffd_flags_t flags) |
| 252 | { |
| 253 | struct inode *inode = file_inode(dst_vma->vm_file); |
| 254 | pgoff_t pgoff = linear_page_index(dst_vma, dst_addr); |
| 255 | struct folio *folio; |
| 256 | struct page *page; |
| 257 | int ret; |
| 258 | |
| 259 | ret = shmem_get_folio(inode, pgoff, &folio, SGP_NOALLOC); |
| 260 | /* Our caller expects us to return -EFAULT if we failed to find folio */ |
| 261 | if (ret == -ENOENT) |
| 262 | ret = -EFAULT; |
| 263 | if (ret) |
| 264 | goto out; |
| 265 | if (!folio) { |
| 266 | ret = -EFAULT; |
| 267 | goto out; |
| 268 | } |
| 269 | |
| 270 | page = folio_file_page(folio, pgoff); |
| 271 | if (PageHWPoison(page)) { |
| 272 | ret = -EIO; |
| 273 | goto out_release; |
| 274 | } |
| 275 | |
| 276 | ret = mfill_atomic_install_pte(dst_pmd, dst_vma, dst_addr, |
| 277 | page, false, flags); |
| 278 | if (ret) |
| 279 | goto out_release; |
| 280 | |
| 281 | folio_unlock(folio); |
| 282 | ret = 0; |
| 283 | out: |
| 284 | return ret; |
| 285 | out_release: |
| 286 | folio_unlock(folio); |
| 287 | folio_put(folio); |
| 288 | goto out; |
| 289 | } |
| 290 | |
| 291 | /* Handles UFFDIO_POISON for all non-hugetlb VMAs. */ |
| 292 | static int mfill_atomic_pte_poison(pmd_t *dst_pmd, |
| 293 | struct vm_area_struct *dst_vma, |
| 294 | unsigned long dst_addr, |
| 295 | uffd_flags_t flags) |
| 296 | { |
| 297 | int ret; |
| 298 | struct mm_struct *dst_mm = dst_vma->vm_mm; |
| 299 | pte_t _dst_pte, *dst_pte; |
| 300 | spinlock_t *ptl; |
| 301 | |
| 302 | _dst_pte = make_pte_marker(PTE_MARKER_POISONED); |
| 303 | ret = -EAGAIN; |
| 304 | dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl); |
| 305 | if (!dst_pte) |
| 306 | goto out; |
| 307 | |
| 308 | if (mfill_file_over_size(dst_vma, dst_addr)) { |
| 309 | ret = -EFAULT; |
| 310 | goto out_unlock; |
| 311 | } |
| 312 | |
| 313 | ret = -EEXIST; |
| 314 | /* Refuse to overwrite any PTE, even a PTE marker (e.g. UFFD WP). */ |
| 315 | if (!pte_none(ptep_get(dst_pte))) |
| 316 | goto out_unlock; |
| 317 | |
| 318 | set_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte); |
| 319 | |
| 320 | /* No need to invalidate - it was non-present before */ |
| 321 | update_mmu_cache(dst_vma, dst_addr, dst_pte); |
| 322 | ret = 0; |
| 323 | out_unlock: |
| 324 | pte_unmap_unlock(dst_pte, ptl); |
| 325 | out: |
| 326 | return ret; |
| 327 | } |
| 328 | |
| 329 | static pmd_t *mm_alloc_pmd(struct mm_struct *mm, unsigned long address) |
| 330 | { |
| 331 | pgd_t *pgd; |
| 332 | p4d_t *p4d; |
| 333 | pud_t *pud; |
| 334 | |
| 335 | pgd = pgd_offset(mm, address); |
| 336 | p4d = p4d_alloc(mm, pgd, address); |
| 337 | if (!p4d) |
| 338 | return NULL; |
| 339 | pud = pud_alloc(mm, p4d, address); |
| 340 | if (!pud) |
| 341 | return NULL; |
| 342 | /* |
| 343 | * Note that we didn't run this because the pmd was |
| 344 | * missing, the *pmd may be already established and in |
| 345 | * turn it may also be a trans_huge_pmd. |
| 346 | */ |
| 347 | return pmd_alloc(mm, pud, address); |
| 348 | } |
| 349 | |
| 350 | #ifdef CONFIG_HUGETLB_PAGE |
| 351 | /* |
| 352 | * mfill_atomic processing for HUGETLB vmas. Note that this routine is |
| 353 | * called with mmap_lock held, it will release mmap_lock before returning. |
| 354 | */ |
| 355 | static __always_inline ssize_t mfill_atomic_hugetlb( |
| 356 | struct vm_area_struct *dst_vma, |
| 357 | unsigned long dst_start, |
| 358 | unsigned long src_start, |
| 359 | unsigned long len, |
| 360 | uffd_flags_t flags) |
| 361 | { |
| 362 | struct mm_struct *dst_mm = dst_vma->vm_mm; |
| 363 | int vm_shared = dst_vma->vm_flags & VM_SHARED; |
| 364 | ssize_t err; |
| 365 | pte_t *dst_pte; |
| 366 | unsigned long src_addr, dst_addr; |
| 367 | long copied; |
| 368 | struct folio *folio; |
| 369 | unsigned long vma_hpagesize; |
| 370 | pgoff_t idx; |
| 371 | u32 hash; |
| 372 | struct address_space *mapping; |
| 373 | |
| 374 | /* |
| 375 | * There is no default zero huge page for all huge page sizes as |
| 376 | * supported by hugetlb. A PMD_SIZE huge pages may exist as used |
| 377 | * by THP. Since we can not reliably insert a zero page, this |
| 378 | * feature is not supported. |
| 379 | */ |
| 380 | if (uffd_flags_mode_is(flags, MFILL_ATOMIC_ZEROPAGE)) { |
| 381 | mmap_read_unlock(dst_mm); |
| 382 | return -EINVAL; |
| 383 | } |
| 384 | |
| 385 | src_addr = src_start; |
| 386 | dst_addr = dst_start; |
| 387 | copied = 0; |
| 388 | folio = NULL; |
| 389 | vma_hpagesize = vma_kernel_pagesize(dst_vma); |
| 390 | |
| 391 | /* |
| 392 | * Validate alignment based on huge page size |
| 393 | */ |
| 394 | err = -EINVAL; |
| 395 | if (dst_start & (vma_hpagesize - 1) || len & (vma_hpagesize - 1)) |
| 396 | goto out_unlock; |
| 397 | |
| 398 | retry: |
| 399 | /* |
| 400 | * On routine entry dst_vma is set. If we had to drop mmap_lock and |
| 401 | * retry, dst_vma will be set to NULL and we must lookup again. |
| 402 | */ |
| 403 | if (!dst_vma) { |
| 404 | err = -ENOENT; |
| 405 | dst_vma = find_dst_vma(dst_mm, dst_start, len); |
| 406 | if (!dst_vma || !is_vm_hugetlb_page(dst_vma)) |
| 407 | goto out_unlock; |
| 408 | |
| 409 | err = -EINVAL; |
| 410 | if (vma_hpagesize != vma_kernel_pagesize(dst_vma)) |
| 411 | goto out_unlock; |
| 412 | |
| 413 | vm_shared = dst_vma->vm_flags & VM_SHARED; |
| 414 | } |
| 415 | |
| 416 | /* |
| 417 | * If not shared, ensure the dst_vma has a anon_vma. |
| 418 | */ |
| 419 | err = -ENOMEM; |
| 420 | if (!vm_shared) { |
| 421 | if (unlikely(anon_vma_prepare(dst_vma))) |
| 422 | goto out_unlock; |
| 423 | } |
| 424 | |
| 425 | while (src_addr < src_start + len) { |
| 426 | BUG_ON(dst_addr >= dst_start + len); |
| 427 | |
| 428 | /* |
| 429 | * Serialize via vma_lock and hugetlb_fault_mutex. |
| 430 | * vma_lock ensures the dst_pte remains valid even |
| 431 | * in the case of shared pmds. fault mutex prevents |
| 432 | * races with other faulting threads. |
| 433 | */ |
| 434 | idx = linear_page_index(dst_vma, dst_addr); |
| 435 | mapping = dst_vma->vm_file->f_mapping; |
| 436 | hash = hugetlb_fault_mutex_hash(mapping, idx); |
| 437 | mutex_lock(&hugetlb_fault_mutex_table[hash]); |
| 438 | hugetlb_vma_lock_read(dst_vma); |
| 439 | |
| 440 | err = -ENOMEM; |
| 441 | dst_pte = huge_pte_alloc(dst_mm, dst_vma, dst_addr, vma_hpagesize); |
| 442 | if (!dst_pte) { |
| 443 | hugetlb_vma_unlock_read(dst_vma); |
| 444 | mutex_unlock(&hugetlb_fault_mutex_table[hash]); |
| 445 | goto out_unlock; |
| 446 | } |
| 447 | |
| 448 | if (!uffd_flags_mode_is(flags, MFILL_ATOMIC_CONTINUE) && |
| 449 | !huge_pte_none_mostly(huge_ptep_get(dst_pte))) { |
| 450 | err = -EEXIST; |
| 451 | hugetlb_vma_unlock_read(dst_vma); |
| 452 | mutex_unlock(&hugetlb_fault_mutex_table[hash]); |
| 453 | goto out_unlock; |
| 454 | } |
| 455 | |
| 456 | err = hugetlb_mfill_atomic_pte(dst_pte, dst_vma, dst_addr, |
| 457 | src_addr, flags, &folio); |
| 458 | |
| 459 | hugetlb_vma_unlock_read(dst_vma); |
| 460 | mutex_unlock(&hugetlb_fault_mutex_table[hash]); |
| 461 | |
| 462 | cond_resched(); |
| 463 | |
| 464 | if (unlikely(err == -ENOENT)) { |
| 465 | mmap_read_unlock(dst_mm); |
| 466 | BUG_ON(!folio); |
| 467 | |
| 468 | err = copy_folio_from_user(folio, |
| 469 | (const void __user *)src_addr, true); |
| 470 | if (unlikely(err)) { |
| 471 | err = -EFAULT; |
| 472 | goto out; |
| 473 | } |
| 474 | mmap_read_lock(dst_mm); |
| 475 | |
| 476 | dst_vma = NULL; |
| 477 | goto retry; |
| 478 | } else |
| 479 | BUG_ON(folio); |
| 480 | |
| 481 | if (!err) { |
| 482 | dst_addr += vma_hpagesize; |
| 483 | src_addr += vma_hpagesize; |
| 484 | copied += vma_hpagesize; |
| 485 | |
| 486 | if (fatal_signal_pending(current)) |
| 487 | err = -EINTR; |
| 488 | } |
| 489 | if (err) |
| 490 | break; |
| 491 | } |
| 492 | |
| 493 | out_unlock: |
| 494 | mmap_read_unlock(dst_mm); |
| 495 | out: |
| 496 | if (folio) |
| 497 | folio_put(folio); |
| 498 | BUG_ON(copied < 0); |
| 499 | BUG_ON(err > 0); |
| 500 | BUG_ON(!copied && !err); |
| 501 | return copied ? copied : err; |
| 502 | } |
| 503 | #else /* !CONFIG_HUGETLB_PAGE */ |
| 504 | /* fail at build time if gcc attempts to use this */ |
| 505 | extern ssize_t mfill_atomic_hugetlb(struct vm_area_struct *dst_vma, |
| 506 | unsigned long dst_start, |
| 507 | unsigned long src_start, |
| 508 | unsigned long len, |
| 509 | uffd_flags_t flags); |
| 510 | #endif /* CONFIG_HUGETLB_PAGE */ |
| 511 | |
| 512 | static __always_inline ssize_t mfill_atomic_pte(pmd_t *dst_pmd, |
| 513 | struct vm_area_struct *dst_vma, |
| 514 | unsigned long dst_addr, |
| 515 | unsigned long src_addr, |
| 516 | uffd_flags_t flags, |
| 517 | struct folio **foliop) |
| 518 | { |
| 519 | ssize_t err; |
| 520 | |
| 521 | if (uffd_flags_mode_is(flags, MFILL_ATOMIC_CONTINUE)) { |
| 522 | return mfill_atomic_pte_continue(dst_pmd, dst_vma, |
| 523 | dst_addr, flags); |
| 524 | } else if (uffd_flags_mode_is(flags, MFILL_ATOMIC_POISON)) { |
| 525 | return mfill_atomic_pte_poison(dst_pmd, dst_vma, |
| 526 | dst_addr, flags); |
| 527 | } |
| 528 | |
| 529 | /* |
| 530 | * The normal page fault path for a shmem will invoke the |
| 531 | * fault, fill the hole in the file and COW it right away. The |
| 532 | * result generates plain anonymous memory. So when we are |
| 533 | * asked to fill an hole in a MAP_PRIVATE shmem mapping, we'll |
| 534 | * generate anonymous memory directly without actually filling |
| 535 | * the hole. For the MAP_PRIVATE case the robustness check |
| 536 | * only happens in the pagetable (to verify it's still none) |
| 537 | * and not in the radix tree. |
| 538 | */ |
| 539 | if (!(dst_vma->vm_flags & VM_SHARED)) { |
| 540 | if (uffd_flags_mode_is(flags, MFILL_ATOMIC_COPY)) |
| 541 | err = mfill_atomic_pte_copy(dst_pmd, dst_vma, |
| 542 | dst_addr, src_addr, |
| 543 | flags, foliop); |
| 544 | else |
| 545 | err = mfill_atomic_pte_zeropage(dst_pmd, |
| 546 | dst_vma, dst_addr); |
| 547 | } else { |
| 548 | err = shmem_mfill_atomic_pte(dst_pmd, dst_vma, |
| 549 | dst_addr, src_addr, |
| 550 | flags, foliop); |
| 551 | } |
| 552 | |
| 553 | return err; |
| 554 | } |
| 555 | |
| 556 | static __always_inline ssize_t mfill_atomic(struct mm_struct *dst_mm, |
| 557 | unsigned long dst_start, |
| 558 | unsigned long src_start, |
| 559 | unsigned long len, |
| 560 | atomic_t *mmap_changing, |
| 561 | uffd_flags_t flags) |
| 562 | { |
| 563 | struct vm_area_struct *dst_vma; |
| 564 | ssize_t err; |
| 565 | pmd_t *dst_pmd; |
| 566 | unsigned long src_addr, dst_addr; |
| 567 | long copied; |
| 568 | struct folio *folio; |
| 569 | |
| 570 | /* |
| 571 | * Sanitize the command parameters: |
| 572 | */ |
| 573 | BUG_ON(dst_start & ~PAGE_MASK); |
| 574 | BUG_ON(len & ~PAGE_MASK); |
| 575 | |
| 576 | /* Does the address range wrap, or is the span zero-sized? */ |
| 577 | BUG_ON(src_start + len <= src_start); |
| 578 | BUG_ON(dst_start + len <= dst_start); |
| 579 | |
| 580 | src_addr = src_start; |
| 581 | dst_addr = dst_start; |
| 582 | copied = 0; |
| 583 | folio = NULL; |
| 584 | retry: |
| 585 | mmap_read_lock(dst_mm); |
| 586 | |
| 587 | /* |
| 588 | * If memory mappings are changing because of non-cooperative |
| 589 | * operation (e.g. mremap) running in parallel, bail out and |
| 590 | * request the user to retry later |
| 591 | */ |
| 592 | err = -EAGAIN; |
| 593 | if (mmap_changing && atomic_read(mmap_changing)) |
| 594 | goto out_unlock; |
| 595 | |
| 596 | /* |
| 597 | * Make sure the vma is not shared, that the dst range is |
| 598 | * both valid and fully within a single existing vma. |
| 599 | */ |
| 600 | err = -ENOENT; |
| 601 | dst_vma = find_dst_vma(dst_mm, dst_start, len); |
| 602 | if (!dst_vma) |
| 603 | goto out_unlock; |
| 604 | |
| 605 | err = -EINVAL; |
| 606 | /* |
| 607 | * shmem_zero_setup is invoked in mmap for MAP_ANONYMOUS|MAP_SHARED but |
| 608 | * it will overwrite vm_ops, so vma_is_anonymous must return false. |
| 609 | */ |
| 610 | if (WARN_ON_ONCE(vma_is_anonymous(dst_vma) && |
| 611 | dst_vma->vm_flags & VM_SHARED)) |
| 612 | goto out_unlock; |
| 613 | |
| 614 | /* |
| 615 | * validate 'mode' now that we know the dst_vma: don't allow |
| 616 | * a wrprotect copy if the userfaultfd didn't register as WP. |
| 617 | */ |
| 618 | if ((flags & MFILL_ATOMIC_WP) && !(dst_vma->vm_flags & VM_UFFD_WP)) |
| 619 | goto out_unlock; |
| 620 | |
| 621 | /* |
| 622 | * If this is a HUGETLB vma, pass off to appropriate routine |
| 623 | */ |
| 624 | if (is_vm_hugetlb_page(dst_vma)) |
| 625 | return mfill_atomic_hugetlb(dst_vma, dst_start, |
| 626 | src_start, len, flags); |
| 627 | |
| 628 | if (!vma_is_anonymous(dst_vma) && !vma_is_shmem(dst_vma)) |
| 629 | goto out_unlock; |
| 630 | if (!vma_is_shmem(dst_vma) && |
| 631 | uffd_flags_mode_is(flags, MFILL_ATOMIC_CONTINUE)) |
| 632 | goto out_unlock; |
| 633 | |
| 634 | /* |
| 635 | * Ensure the dst_vma has a anon_vma or this page |
| 636 | * would get a NULL anon_vma when moved in the |
| 637 | * dst_vma. |
| 638 | */ |
| 639 | err = -ENOMEM; |
| 640 | if (!(dst_vma->vm_flags & VM_SHARED) && |
| 641 | unlikely(anon_vma_prepare(dst_vma))) |
| 642 | goto out_unlock; |
| 643 | |
| 644 | while (src_addr < src_start + len) { |
| 645 | pmd_t dst_pmdval; |
| 646 | |
| 647 | BUG_ON(dst_addr >= dst_start + len); |
| 648 | |
| 649 | dst_pmd = mm_alloc_pmd(dst_mm, dst_addr); |
| 650 | if (unlikely(!dst_pmd)) { |
| 651 | err = -ENOMEM; |
| 652 | break; |
| 653 | } |
| 654 | |
| 655 | dst_pmdval = pmdp_get_lockless(dst_pmd); |
| 656 | /* |
| 657 | * If the dst_pmd is mapped as THP don't |
| 658 | * override it and just be strict. |
| 659 | */ |
| 660 | if (unlikely(pmd_trans_huge(dst_pmdval))) { |
| 661 | err = -EEXIST; |
| 662 | break; |
| 663 | } |
| 664 | if (unlikely(pmd_none(dst_pmdval)) && |
| 665 | unlikely(__pte_alloc(dst_mm, dst_pmd))) { |
| 666 | err = -ENOMEM; |
| 667 | break; |
| 668 | } |
| 669 | /* If an huge pmd materialized from under us fail */ |
| 670 | if (unlikely(pmd_trans_huge(*dst_pmd))) { |
| 671 | err = -EFAULT; |
| 672 | break; |
| 673 | } |
| 674 | |
| 675 | BUG_ON(pmd_none(*dst_pmd)); |
| 676 | BUG_ON(pmd_trans_huge(*dst_pmd)); |
| 677 | |
| 678 | err = mfill_atomic_pte(dst_pmd, dst_vma, dst_addr, |
| 679 | src_addr, flags, &folio); |
| 680 | cond_resched(); |
| 681 | |
| 682 | if (unlikely(err == -ENOENT)) { |
| 683 | void *kaddr; |
| 684 | |
| 685 | mmap_read_unlock(dst_mm); |
| 686 | BUG_ON(!folio); |
| 687 | |
| 688 | kaddr = kmap_local_folio(folio, 0); |
| 689 | err = copy_from_user(kaddr, |
| 690 | (const void __user *) src_addr, |
| 691 | PAGE_SIZE); |
| 692 | kunmap_local(kaddr); |
| 693 | if (unlikely(err)) { |
| 694 | err = -EFAULT; |
| 695 | goto out; |
| 696 | } |
| 697 | flush_dcache_folio(folio); |
| 698 | goto retry; |
| 699 | } else |
| 700 | BUG_ON(folio); |
| 701 | |
| 702 | if (!err) { |
| 703 | dst_addr += PAGE_SIZE; |
| 704 | src_addr += PAGE_SIZE; |
| 705 | copied += PAGE_SIZE; |
| 706 | |
| 707 | if (fatal_signal_pending(current)) |
| 708 | err = -EINTR; |
| 709 | } |
| 710 | if (err) |
| 711 | break; |
| 712 | } |
| 713 | |
| 714 | out_unlock: |
| 715 | mmap_read_unlock(dst_mm); |
| 716 | out: |
| 717 | if (folio) |
| 718 | folio_put(folio); |
| 719 | BUG_ON(copied < 0); |
| 720 | BUG_ON(err > 0); |
| 721 | BUG_ON(!copied && !err); |
| 722 | return copied ? copied : err; |
| 723 | } |
| 724 | |
| 725 | ssize_t mfill_atomic_copy(struct mm_struct *dst_mm, unsigned long dst_start, |
| 726 | unsigned long src_start, unsigned long len, |
| 727 | atomic_t *mmap_changing, uffd_flags_t flags) |
| 728 | { |
| 729 | return mfill_atomic(dst_mm, dst_start, src_start, len, mmap_changing, |
| 730 | uffd_flags_set_mode(flags, MFILL_ATOMIC_COPY)); |
| 731 | } |
| 732 | |
| 733 | ssize_t mfill_atomic_zeropage(struct mm_struct *dst_mm, unsigned long start, |
| 734 | unsigned long len, atomic_t *mmap_changing) |
| 735 | { |
| 736 | return mfill_atomic(dst_mm, start, 0, len, mmap_changing, |
| 737 | uffd_flags_set_mode(0, MFILL_ATOMIC_ZEROPAGE)); |
| 738 | } |
| 739 | |
| 740 | ssize_t mfill_atomic_continue(struct mm_struct *dst_mm, unsigned long start, |
| 741 | unsigned long len, atomic_t *mmap_changing, |
| 742 | uffd_flags_t flags) |
| 743 | { |
| 744 | return mfill_atomic(dst_mm, start, 0, len, mmap_changing, |
| 745 | uffd_flags_set_mode(flags, MFILL_ATOMIC_CONTINUE)); |
| 746 | } |
| 747 | |
| 748 | ssize_t mfill_atomic_poison(struct mm_struct *dst_mm, unsigned long start, |
| 749 | unsigned long len, atomic_t *mmap_changing, |
| 750 | uffd_flags_t flags) |
| 751 | { |
| 752 | return mfill_atomic(dst_mm, start, 0, len, mmap_changing, |
| 753 | uffd_flags_set_mode(flags, MFILL_ATOMIC_POISON)); |
| 754 | } |
| 755 | |
| 756 | long uffd_wp_range(struct vm_area_struct *dst_vma, |
| 757 | unsigned long start, unsigned long len, bool enable_wp) |
| 758 | { |
| 759 | unsigned int mm_cp_flags; |
| 760 | struct mmu_gather tlb; |
| 761 | long ret; |
| 762 | |
| 763 | VM_WARN_ONCE(start < dst_vma->vm_start || start + len > dst_vma->vm_end, |
| 764 | "The address range exceeds VMA boundary.\n"); |
| 765 | if (enable_wp) |
| 766 | mm_cp_flags = MM_CP_UFFD_WP; |
| 767 | else |
| 768 | mm_cp_flags = MM_CP_UFFD_WP_RESOLVE; |
| 769 | |
| 770 | /* |
| 771 | * vma->vm_page_prot already reflects that uffd-wp is enabled for this |
| 772 | * VMA (see userfaultfd_set_vm_flags()) and that all PTEs are supposed |
| 773 | * to be write-protected as default whenever protection changes. |
| 774 | * Try upgrading write permissions manually. |
| 775 | */ |
| 776 | if (!enable_wp && vma_wants_manual_pte_write_upgrade(dst_vma)) |
| 777 | mm_cp_flags |= MM_CP_TRY_CHANGE_WRITABLE; |
| 778 | tlb_gather_mmu(&tlb, dst_vma->vm_mm); |
| 779 | ret = change_protection(&tlb, dst_vma, start, start + len, mm_cp_flags); |
| 780 | tlb_finish_mmu(&tlb); |
| 781 | |
| 782 | return ret; |
| 783 | } |
| 784 | |
| 785 | int mwriteprotect_range(struct mm_struct *dst_mm, unsigned long start, |
| 786 | unsigned long len, bool enable_wp, |
| 787 | atomic_t *mmap_changing) |
| 788 | { |
| 789 | unsigned long end = start + len; |
| 790 | unsigned long _start, _end; |
| 791 | struct vm_area_struct *dst_vma; |
| 792 | unsigned long page_mask; |
| 793 | long err; |
| 794 | VMA_ITERATOR(vmi, dst_mm, start); |
| 795 | |
| 796 | /* |
| 797 | * Sanitize the command parameters: |
| 798 | */ |
| 799 | BUG_ON(start & ~PAGE_MASK); |
| 800 | BUG_ON(len & ~PAGE_MASK); |
| 801 | |
| 802 | /* Does the address range wrap, or is the span zero-sized? */ |
| 803 | BUG_ON(start + len <= start); |
| 804 | |
| 805 | mmap_read_lock(dst_mm); |
| 806 | |
| 807 | /* |
| 808 | * If memory mappings are changing because of non-cooperative |
| 809 | * operation (e.g. mremap) running in parallel, bail out and |
| 810 | * request the user to retry later |
| 811 | */ |
| 812 | err = -EAGAIN; |
| 813 | if (mmap_changing && atomic_read(mmap_changing)) |
| 814 | goto out_unlock; |
| 815 | |
| 816 | err = -ENOENT; |
| 817 | for_each_vma_range(vmi, dst_vma, end) { |
| 818 | |
| 819 | if (!userfaultfd_wp(dst_vma)) { |
| 820 | err = -ENOENT; |
| 821 | break; |
| 822 | } |
| 823 | |
| 824 | if (is_vm_hugetlb_page(dst_vma)) { |
| 825 | err = -EINVAL; |
| 826 | page_mask = vma_kernel_pagesize(dst_vma) - 1; |
| 827 | if ((start & page_mask) || (len & page_mask)) |
| 828 | break; |
| 829 | } |
| 830 | |
| 831 | _start = max(dst_vma->vm_start, start); |
| 832 | _end = min(dst_vma->vm_end, end); |
| 833 | |
| 834 | err = uffd_wp_range(dst_vma, _start, _end - _start, enable_wp); |
| 835 | |
| 836 | /* Return 0 on success, <0 on failures */ |
| 837 | if (err < 0) |
| 838 | break; |
| 839 | err = 0; |
| 840 | } |
| 841 | out_unlock: |
| 842 | mmap_read_unlock(dst_mm); |
| 843 | return err; |
| 844 | } |
| 845 | |
| 846 | |
| 847 | void double_pt_lock(spinlock_t *ptl1, |
| 848 | spinlock_t *ptl2) |
| 849 | __acquires(ptl1) |
| 850 | __acquires(ptl2) |
| 851 | { |
| 852 | spinlock_t *ptl_tmp; |
| 853 | |
| 854 | if (ptl1 > ptl2) { |
| 855 | /* exchange ptl1 and ptl2 */ |
| 856 | ptl_tmp = ptl1; |
| 857 | ptl1 = ptl2; |
| 858 | ptl2 = ptl_tmp; |
| 859 | } |
| 860 | /* lock in virtual address order to avoid lock inversion */ |
| 861 | spin_lock(ptl1); |
| 862 | if (ptl1 != ptl2) |
| 863 | spin_lock_nested(ptl2, SINGLE_DEPTH_NESTING); |
| 864 | else |
| 865 | __acquire(ptl2); |
| 866 | } |
| 867 | |
| 868 | void double_pt_unlock(spinlock_t *ptl1, |
| 869 | spinlock_t *ptl2) |
| 870 | __releases(ptl1) |
| 871 | __releases(ptl2) |
| 872 | { |
| 873 | spin_unlock(ptl1); |
| 874 | if (ptl1 != ptl2) |
| 875 | spin_unlock(ptl2); |
| 876 | else |
| 877 | __release(ptl2); |
| 878 | } |
| 879 | |
| 880 | |
| 881 | static int move_present_pte(struct mm_struct *mm, |
| 882 | struct vm_area_struct *dst_vma, |
| 883 | struct vm_area_struct *src_vma, |
| 884 | unsigned long dst_addr, unsigned long src_addr, |
| 885 | pte_t *dst_pte, pte_t *src_pte, |
| 886 | pte_t orig_dst_pte, pte_t orig_src_pte, |
| 887 | spinlock_t *dst_ptl, spinlock_t *src_ptl, |
| 888 | struct folio *src_folio) |
| 889 | { |
| 890 | int err = 0; |
| 891 | |
| 892 | double_pt_lock(dst_ptl, src_ptl); |
| 893 | |
| 894 | if (!pte_same(*src_pte, orig_src_pte) || |
| 895 | !pte_same(*dst_pte, orig_dst_pte)) { |
| 896 | err = -EAGAIN; |
| 897 | goto out; |
| 898 | } |
| 899 | if (folio_test_large(src_folio) || |
| 900 | folio_maybe_dma_pinned(src_folio) || |
| 901 | !PageAnonExclusive(&src_folio->page)) { |
| 902 | err = -EBUSY; |
| 903 | goto out; |
| 904 | } |
| 905 | |
| 906 | folio_move_anon_rmap(src_folio, dst_vma); |
| 907 | WRITE_ONCE(src_folio->index, linear_page_index(dst_vma, dst_addr)); |
| 908 | |
| 909 | orig_src_pte = ptep_clear_flush(src_vma, src_addr, src_pte); |
| 910 | /* Folio got pinned from under us. Put it back and fail the move. */ |
| 911 | if (folio_maybe_dma_pinned(src_folio)) { |
| 912 | set_pte_at(mm, src_addr, src_pte, orig_src_pte); |
| 913 | err = -EBUSY; |
| 914 | goto out; |
| 915 | } |
| 916 | |
| 917 | orig_dst_pte = mk_pte(&src_folio->page, dst_vma->vm_page_prot); |
| 918 | /* Follow mremap() behavior and treat the entry dirty after the move */ |
| 919 | orig_dst_pte = pte_mkwrite(pte_mkdirty(orig_dst_pte), dst_vma); |
| 920 | |
| 921 | set_pte_at(mm, dst_addr, dst_pte, orig_dst_pte); |
| 922 | out: |
| 923 | double_pt_unlock(dst_ptl, src_ptl); |
| 924 | return err; |
| 925 | } |
| 926 | |
| 927 | static int move_swap_pte(struct mm_struct *mm, |
| 928 | unsigned long dst_addr, unsigned long src_addr, |
| 929 | pte_t *dst_pte, pte_t *src_pte, |
| 930 | pte_t orig_dst_pte, pte_t orig_src_pte, |
| 931 | spinlock_t *dst_ptl, spinlock_t *src_ptl) |
| 932 | { |
| 933 | if (!pte_swp_exclusive(orig_src_pte)) |
| 934 | return -EBUSY; |
| 935 | |
| 936 | double_pt_lock(dst_ptl, src_ptl); |
| 937 | |
| 938 | if (!pte_same(*src_pte, orig_src_pte) || |
| 939 | !pte_same(*dst_pte, orig_dst_pte)) { |
| 940 | double_pt_unlock(dst_ptl, src_ptl); |
| 941 | return -EAGAIN; |
| 942 | } |
| 943 | |
| 944 | orig_src_pte = ptep_get_and_clear(mm, src_addr, src_pte); |
| 945 | set_pte_at(mm, dst_addr, dst_pte, orig_src_pte); |
| 946 | double_pt_unlock(dst_ptl, src_ptl); |
| 947 | |
| 948 | return 0; |
| 949 | } |
| 950 | |
| 951 | /* |
| 952 | * The mmap_lock for reading is held by the caller. Just move the page |
| 953 | * from src_pmd to dst_pmd if possible, and return true if succeeded |
| 954 | * in moving the page. |
| 955 | */ |
| 956 | static int move_pages_pte(struct mm_struct *mm, pmd_t *dst_pmd, pmd_t *src_pmd, |
| 957 | struct vm_area_struct *dst_vma, |
| 958 | struct vm_area_struct *src_vma, |
| 959 | unsigned long dst_addr, unsigned long src_addr, |
| 960 | __u64 mode) |
| 961 | { |
| 962 | swp_entry_t entry; |
| 963 | pte_t orig_src_pte, orig_dst_pte; |
| 964 | pte_t src_folio_pte; |
| 965 | spinlock_t *src_ptl, *dst_ptl; |
| 966 | pte_t *src_pte = NULL; |
| 967 | pte_t *dst_pte = NULL; |
| 968 | |
| 969 | struct folio *src_folio = NULL; |
| 970 | struct anon_vma *src_anon_vma = NULL; |
| 971 | struct mmu_notifier_range range; |
| 972 | int err = 0; |
| 973 | |
| 974 | flush_cache_range(src_vma, src_addr, src_addr + PAGE_SIZE); |
| 975 | mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, mm, |
| 976 | src_addr, src_addr + PAGE_SIZE); |
| 977 | mmu_notifier_invalidate_range_start(&range); |
| 978 | retry: |
| 979 | dst_pte = pte_offset_map_nolock(mm, dst_pmd, dst_addr, &dst_ptl); |
| 980 | |
| 981 | /* Retry if a huge pmd materialized from under us */ |
| 982 | if (unlikely(!dst_pte)) { |
| 983 | err = -EAGAIN; |
| 984 | goto out; |
| 985 | } |
| 986 | |
| 987 | src_pte = pte_offset_map_nolock(mm, src_pmd, src_addr, &src_ptl); |
| 988 | |
| 989 | /* |
| 990 | * We held the mmap_lock for reading so MADV_DONTNEED |
| 991 | * can zap transparent huge pages under us, or the |
| 992 | * transparent huge page fault can establish new |
| 993 | * transparent huge pages under us. |
| 994 | */ |
| 995 | if (unlikely(!src_pte)) { |
| 996 | err = -EAGAIN; |
| 997 | goto out; |
| 998 | } |
| 999 | |
| 1000 | /* Sanity checks before the operation */ |
| 1001 | if (WARN_ON_ONCE(pmd_none(*dst_pmd)) || WARN_ON_ONCE(pmd_none(*src_pmd)) || |
| 1002 | WARN_ON_ONCE(pmd_trans_huge(*dst_pmd)) || WARN_ON_ONCE(pmd_trans_huge(*src_pmd))) { |
| 1003 | err = -EINVAL; |
| 1004 | goto out; |
| 1005 | } |
| 1006 | |
| 1007 | spin_lock(dst_ptl); |
| 1008 | orig_dst_pte = *dst_pte; |
| 1009 | spin_unlock(dst_ptl); |
| 1010 | if (!pte_none(orig_dst_pte)) { |
| 1011 | err = -EEXIST; |
| 1012 | goto out; |
| 1013 | } |
| 1014 | |
| 1015 | spin_lock(src_ptl); |
| 1016 | orig_src_pte = *src_pte; |
| 1017 | spin_unlock(src_ptl); |
| 1018 | if (pte_none(orig_src_pte)) { |
| 1019 | if (!(mode & UFFDIO_MOVE_MODE_ALLOW_SRC_HOLES)) |
| 1020 | err = -ENOENT; |
| 1021 | else /* nothing to do to move a hole */ |
| 1022 | err = 0; |
| 1023 | goto out; |
| 1024 | } |
| 1025 | |
| 1026 | /* If PTE changed after we locked the folio them start over */ |
| 1027 | if (src_folio && unlikely(!pte_same(src_folio_pte, orig_src_pte))) { |
| 1028 | err = -EAGAIN; |
| 1029 | goto out; |
| 1030 | } |
| 1031 | |
| 1032 | if (pte_present(orig_src_pte)) { |
| 1033 | /* |
| 1034 | * Pin and lock both source folio and anon_vma. Since we are in |
| 1035 | * RCU read section, we can't block, so on contention have to |
| 1036 | * unmap the ptes, obtain the lock and retry. |
| 1037 | */ |
| 1038 | if (!src_folio) { |
| 1039 | struct folio *folio; |
| 1040 | |
| 1041 | /* |
| 1042 | * Pin the page while holding the lock to be sure the |
| 1043 | * page isn't freed under us |
| 1044 | */ |
| 1045 | spin_lock(src_ptl); |
| 1046 | if (!pte_same(orig_src_pte, *src_pte)) { |
| 1047 | spin_unlock(src_ptl); |
| 1048 | err = -EAGAIN; |
| 1049 | goto out; |
| 1050 | } |
| 1051 | |
| 1052 | folio = vm_normal_folio(src_vma, src_addr, orig_src_pte); |
| 1053 | if (!folio || !PageAnonExclusive(&folio->page)) { |
| 1054 | spin_unlock(src_ptl); |
| 1055 | err = -EBUSY; |
| 1056 | goto out; |
| 1057 | } |
| 1058 | |
| 1059 | folio_get(folio); |
| 1060 | src_folio = folio; |
| 1061 | src_folio_pte = orig_src_pte; |
| 1062 | spin_unlock(src_ptl); |
| 1063 | |
| 1064 | if (!folio_trylock(src_folio)) { |
| 1065 | pte_unmap(&orig_src_pte); |
| 1066 | pte_unmap(&orig_dst_pte); |
| 1067 | src_pte = dst_pte = NULL; |
| 1068 | /* now we can block and wait */ |
| 1069 | folio_lock(src_folio); |
| 1070 | goto retry; |
| 1071 | } |
| 1072 | |
| 1073 | if (WARN_ON_ONCE(!folio_test_anon(src_folio))) { |
| 1074 | err = -EBUSY; |
| 1075 | goto out; |
| 1076 | } |
| 1077 | } |
| 1078 | |
| 1079 | /* at this point we have src_folio locked */ |
| 1080 | if (folio_test_large(src_folio)) { |
| 1081 | /* split_folio() can block */ |
| 1082 | pte_unmap(&orig_src_pte); |
| 1083 | pte_unmap(&orig_dst_pte); |
| 1084 | src_pte = dst_pte = NULL; |
| 1085 | err = split_folio(src_folio); |
| 1086 | if (err) |
| 1087 | goto out; |
| 1088 | /* have to reacquire the folio after it got split */ |
| 1089 | folio_unlock(src_folio); |
| 1090 | folio_put(src_folio); |
| 1091 | src_folio = NULL; |
| 1092 | goto retry; |
| 1093 | } |
| 1094 | |
| 1095 | if (!src_anon_vma) { |
| 1096 | /* |
| 1097 | * folio_referenced walks the anon_vma chain |
| 1098 | * without the folio lock. Serialize against it with |
| 1099 | * the anon_vma lock, the folio lock is not enough. |
| 1100 | */ |
| 1101 | src_anon_vma = folio_get_anon_vma(src_folio); |
| 1102 | if (!src_anon_vma) { |
| 1103 | /* page was unmapped from under us */ |
| 1104 | err = -EAGAIN; |
| 1105 | goto out; |
| 1106 | } |
| 1107 | if (!anon_vma_trylock_write(src_anon_vma)) { |
| 1108 | pte_unmap(&orig_src_pte); |
| 1109 | pte_unmap(&orig_dst_pte); |
| 1110 | src_pte = dst_pte = NULL; |
| 1111 | /* now we can block and wait */ |
| 1112 | anon_vma_lock_write(src_anon_vma); |
| 1113 | goto retry; |
| 1114 | } |
| 1115 | } |
| 1116 | |
| 1117 | err = move_present_pte(mm, dst_vma, src_vma, |
| 1118 | dst_addr, src_addr, dst_pte, src_pte, |
| 1119 | orig_dst_pte, orig_src_pte, |
| 1120 | dst_ptl, src_ptl, src_folio); |
| 1121 | } else { |
| 1122 | entry = pte_to_swp_entry(orig_src_pte); |
| 1123 | if (non_swap_entry(entry)) { |
| 1124 | if (is_migration_entry(entry)) { |
| 1125 | pte_unmap(&orig_src_pte); |
| 1126 | pte_unmap(&orig_dst_pte); |
| 1127 | src_pte = dst_pte = NULL; |
| 1128 | migration_entry_wait(mm, src_pmd, src_addr); |
| 1129 | err = -EAGAIN; |
| 1130 | } else |
| 1131 | err = -EFAULT; |
| 1132 | goto out; |
| 1133 | } |
| 1134 | |
| 1135 | err = move_swap_pte(mm, dst_addr, src_addr, |
| 1136 | dst_pte, src_pte, |
| 1137 | orig_dst_pte, orig_src_pte, |
| 1138 | dst_ptl, src_ptl); |
| 1139 | } |
| 1140 | |
| 1141 | out: |
| 1142 | if (src_anon_vma) { |
| 1143 | anon_vma_unlock_write(src_anon_vma); |
| 1144 | put_anon_vma(src_anon_vma); |
| 1145 | } |
| 1146 | if (src_folio) { |
| 1147 | folio_unlock(src_folio); |
| 1148 | folio_put(src_folio); |
| 1149 | } |
| 1150 | if (dst_pte) |
| 1151 | pte_unmap(dst_pte); |
| 1152 | if (src_pte) |
| 1153 | pte_unmap(src_pte); |
| 1154 | mmu_notifier_invalidate_range_end(&range); |
| 1155 | |
| 1156 | return err; |
| 1157 | } |
| 1158 | |
| 1159 | #ifdef CONFIG_TRANSPARENT_HUGEPAGE |
| 1160 | static inline bool move_splits_huge_pmd(unsigned long dst_addr, |
| 1161 | unsigned long src_addr, |
| 1162 | unsigned long src_end) |
| 1163 | { |
| 1164 | return (src_addr & ~HPAGE_PMD_MASK) || (dst_addr & ~HPAGE_PMD_MASK) || |
| 1165 | src_end - src_addr < HPAGE_PMD_SIZE; |
| 1166 | } |
| 1167 | #else |
| 1168 | static inline bool move_splits_huge_pmd(unsigned long dst_addr, |
| 1169 | unsigned long src_addr, |
| 1170 | unsigned long src_end) |
| 1171 | { |
| 1172 | /* This is unreachable anyway, just to avoid warnings when HPAGE_PMD_SIZE==0 */ |
| 1173 | return false; |
| 1174 | } |
| 1175 | #endif |
| 1176 | |
| 1177 | static inline bool vma_move_compatible(struct vm_area_struct *vma) |
| 1178 | { |
| 1179 | return !(vma->vm_flags & (VM_PFNMAP | VM_IO | VM_HUGETLB | |
| 1180 | VM_MIXEDMAP | VM_SHADOW_STACK)); |
| 1181 | } |
| 1182 | |
| 1183 | static int validate_move_areas(struct userfaultfd_ctx *ctx, |
| 1184 | struct vm_area_struct *src_vma, |
| 1185 | struct vm_area_struct *dst_vma) |
| 1186 | { |
| 1187 | /* Only allow moving if both have the same access and protection */ |
| 1188 | if ((src_vma->vm_flags & VM_ACCESS_FLAGS) != (dst_vma->vm_flags & VM_ACCESS_FLAGS) || |
| 1189 | pgprot_val(src_vma->vm_page_prot) != pgprot_val(dst_vma->vm_page_prot)) |
| 1190 | return -EINVAL; |
| 1191 | |
| 1192 | /* Only allow moving if both are mlocked or both aren't */ |
| 1193 | if ((src_vma->vm_flags & VM_LOCKED) != (dst_vma->vm_flags & VM_LOCKED)) |
| 1194 | return -EINVAL; |
| 1195 | |
| 1196 | /* |
| 1197 | * For now, we keep it simple and only move between writable VMAs. |
| 1198 | * Access flags are equal, therefore cheching only the source is enough. |
| 1199 | */ |
| 1200 | if (!(src_vma->vm_flags & VM_WRITE)) |
| 1201 | return -EINVAL; |
| 1202 | |
| 1203 | /* Check if vma flags indicate content which can be moved */ |
| 1204 | if (!vma_move_compatible(src_vma) || !vma_move_compatible(dst_vma)) |
| 1205 | return -EINVAL; |
| 1206 | |
| 1207 | /* Ensure dst_vma is registered in uffd we are operating on */ |
| 1208 | if (!dst_vma->vm_userfaultfd_ctx.ctx || |
| 1209 | dst_vma->vm_userfaultfd_ctx.ctx != ctx) |
| 1210 | return -EINVAL; |
| 1211 | |
| 1212 | /* Only allow moving across anonymous vmas */ |
| 1213 | if (!vma_is_anonymous(src_vma) || !vma_is_anonymous(dst_vma)) |
| 1214 | return -EINVAL; |
| 1215 | |
| 1216 | /* |
| 1217 | * Ensure the dst_vma has a anon_vma or this page |
| 1218 | * would get a NULL anon_vma when moved in the |
| 1219 | * dst_vma. |
| 1220 | */ |
| 1221 | if (unlikely(anon_vma_prepare(dst_vma))) |
| 1222 | return -ENOMEM; |
| 1223 | |
| 1224 | return 0; |
| 1225 | } |
| 1226 | |
| 1227 | /** |
| 1228 | * move_pages - move arbitrary anonymous pages of an existing vma |
| 1229 | * @ctx: pointer to the userfaultfd context |
| 1230 | * @mm: the address space to move pages |
| 1231 | * @dst_start: start of the destination virtual memory range |
| 1232 | * @src_start: start of the source virtual memory range |
| 1233 | * @len: length of the virtual memory range |
| 1234 | * @mode: flags from uffdio_move.mode |
| 1235 | * |
| 1236 | * Must be called with mmap_lock held for read. |
| 1237 | * |
| 1238 | * move_pages() remaps arbitrary anonymous pages atomically in zero |
| 1239 | * copy. It only works on non shared anonymous pages because those can |
| 1240 | * be relocated without generating non linear anon_vmas in the rmap |
| 1241 | * code. |
| 1242 | * |
| 1243 | * It provides a zero copy mechanism to handle userspace page faults. |
| 1244 | * The source vma pages should have mapcount == 1, which can be |
| 1245 | * enforced by using madvise(MADV_DONTFORK) on src vma. |
| 1246 | * |
| 1247 | * The thread receiving the page during the userland page fault |
| 1248 | * will receive the faulting page in the source vma through the network, |
| 1249 | * storage or any other I/O device (MADV_DONTFORK in the source vma |
| 1250 | * avoids move_pages() to fail with -EBUSY if the process forks before |
| 1251 | * move_pages() is called), then it will call move_pages() to map the |
| 1252 | * page in the faulting address in the destination vma. |
| 1253 | * |
| 1254 | * This userfaultfd command works purely via pagetables, so it's the |
| 1255 | * most efficient way to move physical non shared anonymous pages |
| 1256 | * across different virtual addresses. Unlike mremap()/mmap()/munmap() |
| 1257 | * it does not create any new vmas. The mapping in the destination |
| 1258 | * address is atomic. |
| 1259 | * |
| 1260 | * It only works if the vma protection bits are identical from the |
| 1261 | * source and destination vma. |
| 1262 | * |
| 1263 | * It can remap non shared anonymous pages within the same vma too. |
| 1264 | * |
| 1265 | * If the source virtual memory range has any unmapped holes, or if |
| 1266 | * the destination virtual memory range is not a whole unmapped hole, |
| 1267 | * move_pages() will fail respectively with -ENOENT or -EEXIST. This |
| 1268 | * provides a very strict behavior to avoid any chance of memory |
| 1269 | * corruption going unnoticed if there are userland race conditions. |
| 1270 | * Only one thread should resolve the userland page fault at any given |
| 1271 | * time for any given faulting address. This means that if two threads |
| 1272 | * try to both call move_pages() on the same destination address at the |
| 1273 | * same time, the second thread will get an explicit error from this |
| 1274 | * command. |
| 1275 | * |
| 1276 | * The command retval will return "len" is successful. The command |
| 1277 | * however can be interrupted by fatal signals or errors. If |
| 1278 | * interrupted it will return the number of bytes successfully |
| 1279 | * remapped before the interruption if any, or the negative error if |
| 1280 | * none. It will never return zero. Either it will return an error or |
| 1281 | * an amount of bytes successfully moved. If the retval reports a |
| 1282 | * "short" remap, the move_pages() command should be repeated by |
| 1283 | * userland with src+retval, dst+reval, len-retval if it wants to know |
| 1284 | * about the error that interrupted it. |
| 1285 | * |
| 1286 | * The UFFDIO_MOVE_MODE_ALLOW_SRC_HOLES flag can be specified to |
| 1287 | * prevent -ENOENT errors to materialize if there are holes in the |
| 1288 | * source virtual range that is being remapped. The holes will be |
| 1289 | * accounted as successfully remapped in the retval of the |
| 1290 | * command. This is mostly useful to remap hugepage naturally aligned |
| 1291 | * virtual regions without knowing if there are transparent hugepage |
| 1292 | * in the regions or not, but preventing the risk of having to split |
| 1293 | * the hugepmd during the remap. |
| 1294 | * |
| 1295 | * If there's any rmap walk that is taking the anon_vma locks without |
| 1296 | * first obtaining the folio lock (the only current instance is |
| 1297 | * folio_referenced), they will have to verify if the folio->mapping |
| 1298 | * has changed after taking the anon_vma lock. If it changed they |
| 1299 | * should release the lock and retry obtaining a new anon_vma, because |
| 1300 | * it means the anon_vma was changed by move_pages() before the lock |
| 1301 | * could be obtained. This is the only additional complexity added to |
| 1302 | * the rmap code to provide this anonymous page remapping functionality. |
| 1303 | */ |
| 1304 | ssize_t move_pages(struct userfaultfd_ctx *ctx, struct mm_struct *mm, |
| 1305 | unsigned long dst_start, unsigned long src_start, |
| 1306 | unsigned long len, __u64 mode) |
| 1307 | { |
| 1308 | struct vm_area_struct *src_vma, *dst_vma; |
| 1309 | unsigned long src_addr, dst_addr; |
| 1310 | pmd_t *src_pmd, *dst_pmd; |
| 1311 | long err = -EINVAL; |
| 1312 | ssize_t moved = 0; |
| 1313 | |
| 1314 | /* Sanitize the command parameters. */ |
| 1315 | if (WARN_ON_ONCE(src_start & ~PAGE_MASK) || |
| 1316 | WARN_ON_ONCE(dst_start & ~PAGE_MASK) || |
| 1317 | WARN_ON_ONCE(len & ~PAGE_MASK)) |
| 1318 | goto out; |
| 1319 | |
| 1320 | /* Does the address range wrap, or is the span zero-sized? */ |
| 1321 | if (WARN_ON_ONCE(src_start + len <= src_start) || |
| 1322 | WARN_ON_ONCE(dst_start + len <= dst_start)) |
| 1323 | goto out; |
| 1324 | |
| 1325 | /* |
| 1326 | * Make sure the vma is not shared, that the src and dst remap |
| 1327 | * ranges are both valid and fully within a single existing |
| 1328 | * vma. |
| 1329 | */ |
| 1330 | src_vma = find_vma(mm, src_start); |
| 1331 | if (!src_vma || (src_vma->vm_flags & VM_SHARED)) |
| 1332 | goto out; |
| 1333 | if (src_start < src_vma->vm_start || |
| 1334 | src_start + len > src_vma->vm_end) |
| 1335 | goto out; |
| 1336 | |
| 1337 | dst_vma = find_vma(mm, dst_start); |
| 1338 | if (!dst_vma || (dst_vma->vm_flags & VM_SHARED)) |
| 1339 | goto out; |
| 1340 | if (dst_start < dst_vma->vm_start || |
| 1341 | dst_start + len > dst_vma->vm_end) |
| 1342 | goto out; |
| 1343 | |
| 1344 | err = validate_move_areas(ctx, src_vma, dst_vma); |
| 1345 | if (err) |
| 1346 | goto out; |
| 1347 | |
| 1348 | for (src_addr = src_start, dst_addr = dst_start; |
| 1349 | src_addr < src_start + len;) { |
| 1350 | spinlock_t *ptl; |
| 1351 | pmd_t dst_pmdval; |
| 1352 | unsigned long step_size; |
| 1353 | |
| 1354 | /* |
| 1355 | * Below works because anonymous area would not have a |
| 1356 | * transparent huge PUD. If file-backed support is added, |
| 1357 | * that case would need to be handled here. |
| 1358 | */ |
| 1359 | src_pmd = mm_find_pmd(mm, src_addr); |
| 1360 | if (unlikely(!src_pmd)) { |
| 1361 | if (!(mode & UFFDIO_MOVE_MODE_ALLOW_SRC_HOLES)) { |
| 1362 | err = -ENOENT; |
| 1363 | break; |
| 1364 | } |
| 1365 | src_pmd = mm_alloc_pmd(mm, src_addr); |
| 1366 | if (unlikely(!src_pmd)) { |
| 1367 | err = -ENOMEM; |
| 1368 | break; |
| 1369 | } |
| 1370 | } |
| 1371 | dst_pmd = mm_alloc_pmd(mm, dst_addr); |
| 1372 | if (unlikely(!dst_pmd)) { |
| 1373 | err = -ENOMEM; |
| 1374 | break; |
| 1375 | } |
| 1376 | |
| 1377 | dst_pmdval = pmdp_get_lockless(dst_pmd); |
| 1378 | /* |
| 1379 | * If the dst_pmd is mapped as THP don't override it and just |
| 1380 | * be strict. If dst_pmd changes into TPH after this check, the |
| 1381 | * move_pages_huge_pmd() will detect the change and retry |
| 1382 | * while move_pages_pte() will detect the change and fail. |
| 1383 | */ |
| 1384 | if (unlikely(pmd_trans_huge(dst_pmdval))) { |
| 1385 | err = -EEXIST; |
| 1386 | break; |
| 1387 | } |
| 1388 | |
| 1389 | ptl = pmd_trans_huge_lock(src_pmd, src_vma); |
| 1390 | if (ptl) { |
| 1391 | if (pmd_devmap(*src_pmd)) { |
| 1392 | spin_unlock(ptl); |
| 1393 | err = -ENOENT; |
| 1394 | break; |
| 1395 | } |
| 1396 | /* Avoid moving zeropages for now */ |
| 1397 | if (is_huge_zero_pmd(*src_pmd)) { |
| 1398 | spin_unlock(ptl); |
| 1399 | err = -EBUSY; |
| 1400 | break; |
| 1401 | } |
| 1402 | |
| 1403 | /* Check if we can move the pmd without splitting it. */ |
| 1404 | if (move_splits_huge_pmd(dst_addr, src_addr, src_start + len) || |
| 1405 | !pmd_none(dst_pmdval)) { |
| 1406 | struct folio *folio = pfn_folio(pmd_pfn(*src_pmd)); |
| 1407 | |
| 1408 | if (!folio || !PageAnonExclusive(&folio->page)) { |
| 1409 | spin_unlock(ptl); |
| 1410 | err = -EBUSY; |
| 1411 | break; |
| 1412 | } |
| 1413 | |
| 1414 | spin_unlock(ptl); |
| 1415 | split_huge_pmd(src_vma, src_pmd, src_addr); |
| 1416 | /* The folio will be split by move_pages_pte() */ |
| 1417 | continue; |
| 1418 | } |
| 1419 | |
| 1420 | err = move_pages_huge_pmd(mm, dst_pmd, src_pmd, |
| 1421 | dst_pmdval, dst_vma, src_vma, |
| 1422 | dst_addr, src_addr); |
| 1423 | step_size = HPAGE_PMD_SIZE; |
| 1424 | } else { |
| 1425 | if (pmd_none(*src_pmd)) { |
| 1426 | if (!(mode & UFFDIO_MOVE_MODE_ALLOW_SRC_HOLES)) { |
| 1427 | err = -ENOENT; |
| 1428 | break; |
| 1429 | } |
| 1430 | if (unlikely(__pte_alloc(mm, src_pmd))) { |
| 1431 | err = -ENOMEM; |
| 1432 | break; |
| 1433 | } |
| 1434 | } |
| 1435 | |
| 1436 | if (unlikely(pte_alloc(mm, dst_pmd))) { |
| 1437 | err = -ENOMEM; |
| 1438 | break; |
| 1439 | } |
| 1440 | |
| 1441 | err = move_pages_pte(mm, dst_pmd, src_pmd, |
| 1442 | dst_vma, src_vma, |
| 1443 | dst_addr, src_addr, mode); |
| 1444 | step_size = PAGE_SIZE; |
| 1445 | } |
| 1446 | |
| 1447 | cond_resched(); |
| 1448 | |
| 1449 | if (fatal_signal_pending(current)) { |
| 1450 | /* Do not override an error */ |
| 1451 | if (!err || err == -EAGAIN) |
| 1452 | err = -EINTR; |
| 1453 | break; |
| 1454 | } |
| 1455 | |
| 1456 | if (err) { |
| 1457 | if (err == -EAGAIN) |
| 1458 | continue; |
| 1459 | break; |
| 1460 | } |
| 1461 | |
| 1462 | /* Proceed to the next page */ |
| 1463 | dst_addr += step_size; |
| 1464 | src_addr += step_size; |
| 1465 | moved += step_size; |
| 1466 | } |
| 1467 | |
| 1468 | out: |
| 1469 | VM_WARN_ON(moved < 0); |
| 1470 | VM_WARN_ON(err > 0); |
| 1471 | VM_WARN_ON(!moved && !err); |
| 1472 | return moved ? moved : err; |
| 1473 | } |