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(page); 68 spinlock_t *ptl; 69 struct folio *folio; 70 struct inode *inode; 71 pgoff_t offset, max_off; 72 73 _dst_pte = mk_pte(page, dst_vma->vm_page_prot); 74 _dst_pte = pte_mkdirty(_dst_pte); 75 if (page_in_cache && !vm_shared) 76 writable = false; 77 78 /* 79 * Always mark a PTE as write-protected when needed, regardless of 80 * VM_WRITE, which the user might change. 81 */ 82 if (wp_copy) { 83 _dst_pte = pte_mkuffd_wp(_dst_pte); 84 writable = false; 85 } 86 87 if (writable) 88 _dst_pte = pte_mkwrite(_dst_pte); 89 else 90 /* 91 * We need this to make sure write bit removed; as mk_pte() 92 * could return a pte with write bit set. 93 */ 94 _dst_pte = pte_wrprotect(_dst_pte); 95 96 dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl); 97 98 if (vma_is_shmem(dst_vma)) { 99 /* serialize against truncate with the page table lock */ 100 inode = dst_vma->vm_file->f_inode; 101 offset = linear_page_index(dst_vma, dst_addr); 102 max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE); 103 ret = -EFAULT; 104 if (unlikely(offset >= max_off)) 105 goto out_unlock; 106 } 107 108 ret = -EEXIST; 109 /* 110 * We allow to overwrite a pte marker: consider when both MISSING|WP 111 * registered, we firstly wr-protect a none pte which has no page cache 112 * page backing it, then access the page. 113 */ 114 if (!pte_none_mostly(*dst_pte)) 115 goto out_unlock; 116 117 folio = page_folio(page); 118 if (page_in_cache) { 119 /* Usually, cache pages are already added to LRU */ 120 if (newly_allocated) 121 folio_add_lru(folio); 122 page_add_file_rmap(page, dst_vma, false); 123 } else { 124 page_add_new_anon_rmap(page, dst_vma, dst_addr); 125 folio_add_lru_vma(folio, dst_vma); 126 } 127 128 /* 129 * Must happen after rmap, as mm_counter() checks mapping (via 130 * PageAnon()), which is set by __page_set_anon_rmap(). 131 */ 132 inc_mm_counter(dst_mm, mm_counter(page)); 133 134 set_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte); 135 136 /* No need to invalidate - it was non-present before */ 137 update_mmu_cache(dst_vma, dst_addr, dst_pte); 138 ret = 0; 139 out_unlock: 140 pte_unmap_unlock(dst_pte, ptl); 141 return ret; 142 } 143 144 static int mcopy_atomic_pte(struct mm_struct *dst_mm, 145 pmd_t *dst_pmd, 146 struct vm_area_struct *dst_vma, 147 unsigned long dst_addr, 148 unsigned long src_addr, 149 struct page **pagep, 150 bool wp_copy) 151 { 152 void *page_kaddr; 153 int ret; 154 struct page *page; 155 156 if (!*pagep) { 157 ret = -ENOMEM; 158 page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, dst_vma, dst_addr); 159 if (!page) 160 goto out; 161 162 page_kaddr = kmap_local_page(page); 163 /* 164 * The read mmap_lock is held here. Despite the 165 * mmap_lock being read recursive a deadlock is still 166 * possible if a writer has taken a lock. For example: 167 * 168 * process A thread 1 takes read lock on own mmap_lock 169 * process A thread 2 calls mmap, blocks taking write lock 170 * process B thread 1 takes page fault, read lock on own mmap lock 171 * process B thread 2 calls mmap, blocks taking write lock 172 * process A thread 1 blocks taking read lock on process B 173 * process B thread 1 blocks taking read lock on process A 174 * 175 * Disable page faults to prevent potential deadlock 176 * and retry the copy outside the mmap_lock. 177 */ 178 pagefault_disable(); 179 ret = copy_from_user(page_kaddr, 180 (const void __user *) src_addr, 181 PAGE_SIZE); 182 pagefault_enable(); 183 kunmap_local(page_kaddr); 184 185 /* fallback to copy_from_user outside mmap_lock */ 186 if (unlikely(ret)) { 187 ret = -ENOENT; 188 *pagep = page; 189 /* don't free the page */ 190 goto out; 191 } 192 193 flush_dcache_page(page); 194 } else { 195 page = *pagep; 196 *pagep = NULL; 197 } 198 199 /* 200 * The memory barrier inside __SetPageUptodate makes sure that 201 * preceding stores to the page contents become visible before 202 * the set_pte_at() write. 203 */ 204 __SetPageUptodate(page); 205 206 ret = -ENOMEM; 207 if (mem_cgroup_charge(page_folio(page), dst_mm, GFP_KERNEL)) 208 goto out_release; 209 210 ret = mfill_atomic_install_pte(dst_mm, dst_pmd, dst_vma, dst_addr, 211 page, true, wp_copy); 212 if (ret) 213 goto out_release; 214 out: 215 return ret; 216 out_release: 217 put_page(page); 218 goto out; 219 } 220 221 static int mfill_zeropage_pte(struct mm_struct *dst_mm, 222 pmd_t *dst_pmd, 223 struct vm_area_struct *dst_vma, 224 unsigned long dst_addr) 225 { 226 pte_t _dst_pte, *dst_pte; 227 spinlock_t *ptl; 228 int ret; 229 pgoff_t offset, max_off; 230 struct inode *inode; 231 232 _dst_pte = pte_mkspecial(pfn_pte(my_zero_pfn(dst_addr), 233 dst_vma->vm_page_prot)); 234 dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl); 235 if (dst_vma->vm_file) { 236 /* the shmem MAP_PRIVATE case requires checking the i_size */ 237 inode = dst_vma->vm_file->f_inode; 238 offset = linear_page_index(dst_vma, dst_addr); 239 max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE); 240 ret = -EFAULT; 241 if (unlikely(offset >= max_off)) 242 goto out_unlock; 243 } 244 ret = -EEXIST; 245 if (!pte_none(*dst_pte)) 246 goto out_unlock; 247 set_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte); 248 /* No need to invalidate - it was non-present before */ 249 update_mmu_cache(dst_vma, dst_addr, dst_pte); 250 ret = 0; 251 out_unlock: 252 pte_unmap_unlock(dst_pte, ptl); 253 return ret; 254 } 255 256 /* Handles UFFDIO_CONTINUE for all shmem VMAs (shared or private). */ 257 static int mcontinue_atomic_pte(struct mm_struct *dst_mm, 258 pmd_t *dst_pmd, 259 struct vm_area_struct *dst_vma, 260 unsigned long dst_addr, 261 bool wp_copy) 262 { 263 struct inode *inode = file_inode(dst_vma->vm_file); 264 pgoff_t pgoff = linear_page_index(dst_vma, dst_addr); 265 struct folio *folio; 266 struct page *page; 267 int ret; 268 269 ret = shmem_get_folio(inode, pgoff, &folio, SGP_NOALLOC); 270 /* Our caller expects us to return -EFAULT if we failed to find folio */ 271 if (ret == -ENOENT) 272 ret = -EFAULT; 273 if (ret) 274 goto out; 275 if (!folio) { 276 ret = -EFAULT; 277 goto out; 278 } 279 280 page = folio_file_page(folio, pgoff); 281 if (PageHWPoison(page)) { 282 ret = -EIO; 283 goto out_release; 284 } 285 286 ret = mfill_atomic_install_pte(dst_mm, dst_pmd, dst_vma, dst_addr, 287 page, false, wp_copy); 288 if (ret) 289 goto out_release; 290 291 folio_unlock(folio); 292 ret = 0; 293 out: 294 return ret; 295 out_release: 296 folio_unlock(folio); 297 folio_put(folio); 298 goto out; 299 } 300 301 static pmd_t *mm_alloc_pmd(struct mm_struct *mm, unsigned long address) 302 { 303 pgd_t *pgd; 304 p4d_t *p4d; 305 pud_t *pud; 306 307 pgd = pgd_offset(mm, address); 308 p4d = p4d_alloc(mm, pgd, address); 309 if (!p4d) 310 return NULL; 311 pud = pud_alloc(mm, p4d, address); 312 if (!pud) 313 return NULL; 314 /* 315 * Note that we didn't run this because the pmd was 316 * missing, the *pmd may be already established and in 317 * turn it may also be a trans_huge_pmd. 318 */ 319 return pmd_alloc(mm, pud, address); 320 } 321 322 #ifdef CONFIG_HUGETLB_PAGE 323 /* 324 * __mcopy_atomic processing for HUGETLB vmas. Note that this routine is 325 * called with mmap_lock held, it will release mmap_lock before returning. 326 */ 327 static __always_inline ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm, 328 struct vm_area_struct *dst_vma, 329 unsigned long dst_start, 330 unsigned long src_start, 331 unsigned long len, 332 enum mcopy_atomic_mode mode, 333 bool wp_copy) 334 { 335 int vm_shared = dst_vma->vm_flags & VM_SHARED; 336 ssize_t err; 337 pte_t *dst_pte; 338 unsigned long src_addr, dst_addr; 339 long copied; 340 struct page *page; 341 unsigned long vma_hpagesize; 342 pgoff_t idx; 343 u32 hash; 344 struct address_space *mapping; 345 346 /* 347 * There is no default zero huge page for all huge page sizes as 348 * supported by hugetlb. A PMD_SIZE huge pages may exist as used 349 * by THP. Since we can not reliably insert a zero page, this 350 * feature is not supported. 351 */ 352 if (mode == MCOPY_ATOMIC_ZEROPAGE) { 353 mmap_read_unlock(dst_mm); 354 return -EINVAL; 355 } 356 357 src_addr = src_start; 358 dst_addr = dst_start; 359 copied = 0; 360 page = NULL; 361 vma_hpagesize = vma_kernel_pagesize(dst_vma); 362 363 /* 364 * Validate alignment based on huge page size 365 */ 366 err = -EINVAL; 367 if (dst_start & (vma_hpagesize - 1) || len & (vma_hpagesize - 1)) 368 goto out_unlock; 369 370 retry: 371 /* 372 * On routine entry dst_vma is set. If we had to drop mmap_lock and 373 * retry, dst_vma will be set to NULL and we must lookup again. 374 */ 375 if (!dst_vma) { 376 err = -ENOENT; 377 dst_vma = find_dst_vma(dst_mm, dst_start, len); 378 if (!dst_vma || !is_vm_hugetlb_page(dst_vma)) 379 goto out_unlock; 380 381 err = -EINVAL; 382 if (vma_hpagesize != vma_kernel_pagesize(dst_vma)) 383 goto out_unlock; 384 385 vm_shared = dst_vma->vm_flags & VM_SHARED; 386 } 387 388 /* 389 * If not shared, ensure the dst_vma has a anon_vma. 390 */ 391 err = -ENOMEM; 392 if (!vm_shared) { 393 if (unlikely(anon_vma_prepare(dst_vma))) 394 goto out_unlock; 395 } 396 397 while (src_addr < src_start + len) { 398 BUG_ON(dst_addr >= dst_start + len); 399 400 /* 401 * Serialize via vma_lock and hugetlb_fault_mutex. 402 * vma_lock ensures the dst_pte remains valid even 403 * in the case of shared pmds. fault mutex prevents 404 * races with other faulting threads. 405 */ 406 idx = linear_page_index(dst_vma, dst_addr); 407 mapping = dst_vma->vm_file->f_mapping; 408 hash = hugetlb_fault_mutex_hash(mapping, idx); 409 mutex_lock(&hugetlb_fault_mutex_table[hash]); 410 hugetlb_vma_lock_read(dst_vma); 411 412 err = -ENOMEM; 413 dst_pte = huge_pte_alloc(dst_mm, dst_vma, dst_addr, vma_hpagesize); 414 if (!dst_pte) { 415 hugetlb_vma_unlock_read(dst_vma); 416 mutex_unlock(&hugetlb_fault_mutex_table[hash]); 417 goto out_unlock; 418 } 419 420 if (mode != MCOPY_ATOMIC_CONTINUE && 421 !huge_pte_none_mostly(huge_ptep_get(dst_pte))) { 422 err = -EEXIST; 423 hugetlb_vma_unlock_read(dst_vma); 424 mutex_unlock(&hugetlb_fault_mutex_table[hash]); 425 goto out_unlock; 426 } 427 428 err = hugetlb_mcopy_atomic_pte(dst_mm, dst_pte, dst_vma, 429 dst_addr, src_addr, mode, &page, 430 wp_copy); 431 432 hugetlb_vma_unlock_read(dst_vma); 433 mutex_unlock(&hugetlb_fault_mutex_table[hash]); 434 435 cond_resched(); 436 437 if (unlikely(err == -ENOENT)) { 438 mmap_read_unlock(dst_mm); 439 BUG_ON(!page); 440 441 err = copy_huge_page_from_user(page, 442 (const void __user *)src_addr, 443 vma_hpagesize / PAGE_SIZE, 444 true); 445 if (unlikely(err)) { 446 err = -EFAULT; 447 goto out; 448 } 449 mmap_read_lock(dst_mm); 450 451 dst_vma = NULL; 452 goto retry; 453 } else 454 BUG_ON(page); 455 456 if (!err) { 457 dst_addr += vma_hpagesize; 458 src_addr += vma_hpagesize; 459 copied += vma_hpagesize; 460 461 if (fatal_signal_pending(current)) 462 err = -EINTR; 463 } 464 if (err) 465 break; 466 } 467 468 out_unlock: 469 mmap_read_unlock(dst_mm); 470 out: 471 if (page) 472 put_page(page); 473 BUG_ON(copied < 0); 474 BUG_ON(err > 0); 475 BUG_ON(!copied && !err); 476 return copied ? copied : err; 477 } 478 #else /* !CONFIG_HUGETLB_PAGE */ 479 /* fail at build time if gcc attempts to use this */ 480 extern ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm, 481 struct vm_area_struct *dst_vma, 482 unsigned long dst_start, 483 unsigned long src_start, 484 unsigned long len, 485 enum mcopy_atomic_mode mode, 486 bool wp_copy); 487 #endif /* CONFIG_HUGETLB_PAGE */ 488 489 static __always_inline ssize_t mfill_atomic_pte(struct mm_struct *dst_mm, 490 pmd_t *dst_pmd, 491 struct vm_area_struct *dst_vma, 492 unsigned long dst_addr, 493 unsigned long src_addr, 494 struct page **page, 495 enum mcopy_atomic_mode mode, 496 bool wp_copy) 497 { 498 ssize_t err; 499 500 if (mode == MCOPY_ATOMIC_CONTINUE) { 501 return mcontinue_atomic_pte(dst_mm, dst_pmd, dst_vma, dst_addr, 502 wp_copy); 503 } 504 505 /* 506 * The normal page fault path for a shmem will invoke the 507 * fault, fill the hole in the file and COW it right away. The 508 * result generates plain anonymous memory. So when we are 509 * asked to fill an hole in a MAP_PRIVATE shmem mapping, we'll 510 * generate anonymous memory directly without actually filling 511 * the hole. For the MAP_PRIVATE case the robustness check 512 * only happens in the pagetable (to verify it's still none) 513 * and not in the radix tree. 514 */ 515 if (!(dst_vma->vm_flags & VM_SHARED)) { 516 if (mode == MCOPY_ATOMIC_NORMAL) 517 err = mcopy_atomic_pte(dst_mm, dst_pmd, dst_vma, 518 dst_addr, src_addr, page, 519 wp_copy); 520 else 521 err = mfill_zeropage_pte(dst_mm, dst_pmd, 522 dst_vma, dst_addr); 523 } else { 524 err = shmem_mfill_atomic_pte(dst_mm, dst_pmd, dst_vma, 525 dst_addr, src_addr, 526 mode != MCOPY_ATOMIC_NORMAL, 527 wp_copy, page); 528 } 529 530 return err; 531 } 532 533 static __always_inline ssize_t __mcopy_atomic(struct mm_struct *dst_mm, 534 unsigned long dst_start, 535 unsigned long src_start, 536 unsigned long len, 537 enum mcopy_atomic_mode mcopy_mode, 538 atomic_t *mmap_changing, 539 __u64 mode) 540 { 541 struct vm_area_struct *dst_vma; 542 ssize_t err; 543 pmd_t *dst_pmd; 544 unsigned long src_addr, dst_addr; 545 long copied; 546 struct page *page; 547 bool wp_copy; 548 549 /* 550 * Sanitize the command parameters: 551 */ 552 BUG_ON(dst_start & ~PAGE_MASK); 553 BUG_ON(len & ~PAGE_MASK); 554 555 /* Does the address range wrap, or is the span zero-sized? */ 556 BUG_ON(src_start + len <= src_start); 557 BUG_ON(dst_start + len <= dst_start); 558 559 src_addr = src_start; 560 dst_addr = dst_start; 561 copied = 0; 562 page = NULL; 563 retry: 564 mmap_read_lock(dst_mm); 565 566 /* 567 * If memory mappings are changing because of non-cooperative 568 * operation (e.g. mremap) running in parallel, bail out and 569 * request the user to retry later 570 */ 571 err = -EAGAIN; 572 if (mmap_changing && atomic_read(mmap_changing)) 573 goto out_unlock; 574 575 /* 576 * Make sure the vma is not shared, that the dst range is 577 * both valid and fully within a single existing vma. 578 */ 579 err = -ENOENT; 580 dst_vma = find_dst_vma(dst_mm, dst_start, len); 581 if (!dst_vma) 582 goto out_unlock; 583 584 err = -EINVAL; 585 /* 586 * shmem_zero_setup is invoked in mmap for MAP_ANONYMOUS|MAP_SHARED but 587 * it will overwrite vm_ops, so vma_is_anonymous must return false. 588 */ 589 if (WARN_ON_ONCE(vma_is_anonymous(dst_vma) && 590 dst_vma->vm_flags & VM_SHARED)) 591 goto out_unlock; 592 593 /* 594 * validate 'mode' now that we know the dst_vma: don't allow 595 * a wrprotect copy if the userfaultfd didn't register as WP. 596 */ 597 wp_copy = mode & UFFDIO_COPY_MODE_WP; 598 if (wp_copy && !(dst_vma->vm_flags & VM_UFFD_WP)) 599 goto out_unlock; 600 601 /* 602 * If this is a HUGETLB vma, pass off to appropriate routine 603 */ 604 if (is_vm_hugetlb_page(dst_vma)) 605 return __mcopy_atomic_hugetlb(dst_mm, dst_vma, dst_start, 606 src_start, len, mcopy_mode, 607 wp_copy); 608 609 if (!vma_is_anonymous(dst_vma) && !vma_is_shmem(dst_vma)) 610 goto out_unlock; 611 if (!vma_is_shmem(dst_vma) && mcopy_mode == MCOPY_ATOMIC_CONTINUE) 612 goto out_unlock; 613 614 /* 615 * Ensure the dst_vma has a anon_vma or this page 616 * would get a NULL anon_vma when moved in the 617 * dst_vma. 618 */ 619 err = -ENOMEM; 620 if (!(dst_vma->vm_flags & VM_SHARED) && 621 unlikely(anon_vma_prepare(dst_vma))) 622 goto out_unlock; 623 624 while (src_addr < src_start + len) { 625 pmd_t dst_pmdval; 626 627 BUG_ON(dst_addr >= dst_start + len); 628 629 dst_pmd = mm_alloc_pmd(dst_mm, dst_addr); 630 if (unlikely(!dst_pmd)) { 631 err = -ENOMEM; 632 break; 633 } 634 635 dst_pmdval = pmdp_get_lockless(dst_pmd); 636 /* 637 * If the dst_pmd is mapped as THP don't 638 * override it and just be strict. 639 */ 640 if (unlikely(pmd_trans_huge(dst_pmdval))) { 641 err = -EEXIST; 642 break; 643 } 644 if (unlikely(pmd_none(dst_pmdval)) && 645 unlikely(__pte_alloc(dst_mm, dst_pmd))) { 646 err = -ENOMEM; 647 break; 648 } 649 /* If an huge pmd materialized from under us fail */ 650 if (unlikely(pmd_trans_huge(*dst_pmd))) { 651 err = -EFAULT; 652 break; 653 } 654 655 BUG_ON(pmd_none(*dst_pmd)); 656 BUG_ON(pmd_trans_huge(*dst_pmd)); 657 658 err = mfill_atomic_pte(dst_mm, dst_pmd, dst_vma, dst_addr, 659 src_addr, &page, mcopy_mode, wp_copy); 660 cond_resched(); 661 662 if (unlikely(err == -ENOENT)) { 663 void *page_kaddr; 664 665 mmap_read_unlock(dst_mm); 666 BUG_ON(!page); 667 668 page_kaddr = kmap_local_page(page); 669 err = copy_from_user(page_kaddr, 670 (const void __user *) src_addr, 671 PAGE_SIZE); 672 kunmap_local(page_kaddr); 673 if (unlikely(err)) { 674 err = -EFAULT; 675 goto out; 676 } 677 flush_dcache_page(page); 678 goto retry; 679 } else 680 BUG_ON(page); 681 682 if (!err) { 683 dst_addr += PAGE_SIZE; 684 src_addr += PAGE_SIZE; 685 copied += PAGE_SIZE; 686 687 if (fatal_signal_pending(current)) 688 err = -EINTR; 689 } 690 if (err) 691 break; 692 } 693 694 out_unlock: 695 mmap_read_unlock(dst_mm); 696 out: 697 if (page) 698 put_page(page); 699 BUG_ON(copied < 0); 700 BUG_ON(err > 0); 701 BUG_ON(!copied && !err); 702 return copied ? copied : err; 703 } 704 705 ssize_t mcopy_atomic(struct mm_struct *dst_mm, unsigned long dst_start, 706 unsigned long src_start, unsigned long len, 707 atomic_t *mmap_changing, __u64 mode) 708 { 709 return __mcopy_atomic(dst_mm, dst_start, src_start, len, 710 MCOPY_ATOMIC_NORMAL, mmap_changing, mode); 711 } 712 713 ssize_t mfill_zeropage(struct mm_struct *dst_mm, unsigned long start, 714 unsigned long len, atomic_t *mmap_changing) 715 { 716 return __mcopy_atomic(dst_mm, start, 0, len, MCOPY_ATOMIC_ZEROPAGE, 717 mmap_changing, 0); 718 } 719 720 ssize_t mcopy_continue(struct mm_struct *dst_mm, unsigned long start, 721 unsigned long len, atomic_t *mmap_changing) 722 { 723 return __mcopy_atomic(dst_mm, start, 0, len, MCOPY_ATOMIC_CONTINUE, 724 mmap_changing, 0); 725 } 726 727 void uffd_wp_range(struct mm_struct *dst_mm, struct vm_area_struct *dst_vma, 728 unsigned long start, unsigned long len, bool enable_wp) 729 { 730 struct mmu_gather tlb; 731 pgprot_t newprot; 732 733 if (enable_wp) 734 newprot = vm_get_page_prot(dst_vma->vm_flags & ~(VM_WRITE)); 735 else 736 newprot = vm_get_page_prot(dst_vma->vm_flags); 737 738 tlb_gather_mmu(&tlb, dst_mm); 739 change_protection(&tlb, dst_vma, start, start + len, newprot, 740 enable_wp ? MM_CP_UFFD_WP : MM_CP_UFFD_WP_RESOLVE); 741 tlb_finish_mmu(&tlb); 742 } 743 744 int mwriteprotect_range(struct mm_struct *dst_mm, unsigned long start, 745 unsigned long len, bool enable_wp, 746 atomic_t *mmap_changing) 747 { 748 struct vm_area_struct *dst_vma; 749 unsigned long page_mask; 750 int err; 751 752 /* 753 * Sanitize the command parameters: 754 */ 755 BUG_ON(start & ~PAGE_MASK); 756 BUG_ON(len & ~PAGE_MASK); 757 758 /* Does the address range wrap, or is the span zero-sized? */ 759 BUG_ON(start + len <= start); 760 761 mmap_read_lock(dst_mm); 762 763 /* 764 * If memory mappings are changing because of non-cooperative 765 * operation (e.g. mremap) running in parallel, bail out and 766 * request the user to retry later 767 */ 768 err = -EAGAIN; 769 if (mmap_changing && atomic_read(mmap_changing)) 770 goto out_unlock; 771 772 err = -ENOENT; 773 dst_vma = find_dst_vma(dst_mm, start, len); 774 775 if (!dst_vma) 776 goto out_unlock; 777 if (!userfaultfd_wp(dst_vma)) 778 goto out_unlock; 779 if (!vma_can_userfault(dst_vma, dst_vma->vm_flags)) 780 goto out_unlock; 781 782 if (is_vm_hugetlb_page(dst_vma)) { 783 err = -EINVAL; 784 page_mask = vma_kernel_pagesize(dst_vma) - 1; 785 if ((start & page_mask) || (len & page_mask)) 786 goto out_unlock; 787 } 788 789 uffd_wp_range(dst_mm, dst_vma, start, len, enable_wp); 790 791 err = 0; 792 out_unlock: 793 mmap_read_unlock(dst_mm); 794 return err; 795 } 796