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 } 777