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 page *page; 247 int ret; 248 249 ret = shmem_getpage(inode, pgoff, &page, SGP_NOALLOC); 250 /* Our caller expects us to return -EFAULT if we failed to find page. */ 251 if (ret == -ENOENT) 252 ret = -EFAULT; 253 if (ret) 254 goto out; 255 if (!page) { 256 ret = -EFAULT; 257 goto out; 258 } 259 260 if (PageHWPoison(page)) { 261 ret = -EIO; 262 goto out_release; 263 } 264 265 ret = mfill_atomic_install_pte(dst_mm, dst_pmd, dst_vma, dst_addr, 266 page, false, wp_copy); 267 if (ret) 268 goto out_release; 269 270 unlock_page(page); 271 ret = 0; 272 out: 273 return ret; 274 out_release: 275 unlock_page(page); 276 put_page(page); 277 goto out; 278 } 279 280 static pmd_t *mm_alloc_pmd(struct mm_struct *mm, unsigned long address) 281 { 282 pgd_t *pgd; 283 p4d_t *p4d; 284 pud_t *pud; 285 286 pgd = pgd_offset(mm, address); 287 p4d = p4d_alloc(mm, pgd, address); 288 if (!p4d) 289 return NULL; 290 pud = pud_alloc(mm, p4d, address); 291 if (!pud) 292 return NULL; 293 /* 294 * Note that we didn't run this because the pmd was 295 * missing, the *pmd may be already established and in 296 * turn it may also be a trans_huge_pmd. 297 */ 298 return pmd_alloc(mm, pud, address); 299 } 300 301 #ifdef CONFIG_HUGETLB_PAGE 302 /* 303 * __mcopy_atomic processing for HUGETLB vmas. Note that this routine is 304 * called with mmap_lock held, it will release mmap_lock before returning. 305 */ 306 static __always_inline ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm, 307 struct vm_area_struct *dst_vma, 308 unsigned long dst_start, 309 unsigned long src_start, 310 unsigned long len, 311 enum mcopy_atomic_mode mode, 312 bool wp_copy) 313 { 314 int vm_shared = dst_vma->vm_flags & VM_SHARED; 315 ssize_t err; 316 pte_t *dst_pte; 317 unsigned long src_addr, dst_addr; 318 long copied; 319 struct page *page; 320 unsigned long vma_hpagesize; 321 pgoff_t idx; 322 u32 hash; 323 struct address_space *mapping; 324 325 /* 326 * There is no default zero huge page for all huge page sizes as 327 * supported by hugetlb. A PMD_SIZE huge pages may exist as used 328 * by THP. Since we can not reliably insert a zero page, this 329 * feature is not supported. 330 */ 331 if (mode == MCOPY_ATOMIC_ZEROPAGE) { 332 mmap_read_unlock(dst_mm); 333 return -EINVAL; 334 } 335 336 src_addr = src_start; 337 dst_addr = dst_start; 338 copied = 0; 339 page = NULL; 340 vma_hpagesize = vma_kernel_pagesize(dst_vma); 341 342 /* 343 * Validate alignment based on huge page size 344 */ 345 err = -EINVAL; 346 if (dst_start & (vma_hpagesize - 1) || len & (vma_hpagesize - 1)) 347 goto out_unlock; 348 349 retry: 350 /* 351 * On routine entry dst_vma is set. If we had to drop mmap_lock and 352 * retry, dst_vma will be set to NULL and we must lookup again. 353 */ 354 if (!dst_vma) { 355 err = -ENOENT; 356 dst_vma = find_dst_vma(dst_mm, dst_start, len); 357 if (!dst_vma || !is_vm_hugetlb_page(dst_vma)) 358 goto out_unlock; 359 360 err = -EINVAL; 361 if (vma_hpagesize != vma_kernel_pagesize(dst_vma)) 362 goto out_unlock; 363 364 vm_shared = dst_vma->vm_flags & VM_SHARED; 365 } 366 367 /* 368 * If not shared, ensure the dst_vma has a anon_vma. 369 */ 370 err = -ENOMEM; 371 if (!vm_shared) { 372 if (unlikely(anon_vma_prepare(dst_vma))) 373 goto out_unlock; 374 } 375 376 while (src_addr < src_start + len) { 377 BUG_ON(dst_addr >= dst_start + len); 378 379 /* 380 * Serialize via i_mmap_rwsem and hugetlb_fault_mutex. 381 * i_mmap_rwsem ensures the dst_pte remains valid even 382 * in the case of shared pmds. fault mutex prevents 383 * races with other faulting threads. 384 */ 385 mapping = dst_vma->vm_file->f_mapping; 386 i_mmap_lock_read(mapping); 387 idx = linear_page_index(dst_vma, dst_addr); 388 hash = hugetlb_fault_mutex_hash(mapping, idx); 389 mutex_lock(&hugetlb_fault_mutex_table[hash]); 390 391 err = -ENOMEM; 392 dst_pte = huge_pte_alloc(dst_mm, dst_vma, dst_addr, vma_hpagesize); 393 if (!dst_pte) { 394 mutex_unlock(&hugetlb_fault_mutex_table[hash]); 395 i_mmap_unlock_read(mapping); 396 goto out_unlock; 397 } 398 399 if (mode != MCOPY_ATOMIC_CONTINUE && 400 !huge_pte_none_mostly(huge_ptep_get(dst_pte))) { 401 err = -EEXIST; 402 mutex_unlock(&hugetlb_fault_mutex_table[hash]); 403 i_mmap_unlock_read(mapping); 404 goto out_unlock; 405 } 406 407 err = hugetlb_mcopy_atomic_pte(dst_mm, dst_pte, dst_vma, 408 dst_addr, src_addr, mode, &page, 409 wp_copy); 410 411 mutex_unlock(&hugetlb_fault_mutex_table[hash]); 412 i_mmap_unlock_read(mapping); 413 414 cond_resched(); 415 416 if (unlikely(err == -ENOENT)) { 417 mmap_read_unlock(dst_mm); 418 BUG_ON(!page); 419 420 err = copy_huge_page_from_user(page, 421 (const void __user *)src_addr, 422 vma_hpagesize / PAGE_SIZE, 423 true); 424 if (unlikely(err)) { 425 err = -EFAULT; 426 goto out; 427 } 428 mmap_read_lock(dst_mm); 429 430 dst_vma = NULL; 431 goto retry; 432 } else 433 BUG_ON(page); 434 435 if (!err) { 436 dst_addr += vma_hpagesize; 437 src_addr += vma_hpagesize; 438 copied += vma_hpagesize; 439 440 if (fatal_signal_pending(current)) 441 err = -EINTR; 442 } 443 if (err) 444 break; 445 } 446 447 out_unlock: 448 mmap_read_unlock(dst_mm); 449 out: 450 if (page) 451 put_page(page); 452 BUG_ON(copied < 0); 453 BUG_ON(err > 0); 454 BUG_ON(!copied && !err); 455 return copied ? copied : err; 456 } 457 #else /* !CONFIG_HUGETLB_PAGE */ 458 /* fail at build time if gcc attempts to use this */ 459 extern ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm, 460 struct vm_area_struct *dst_vma, 461 unsigned long dst_start, 462 unsigned long src_start, 463 unsigned long len, 464 enum mcopy_atomic_mode mode, 465 bool wp_copy); 466 #endif /* CONFIG_HUGETLB_PAGE */ 467 468 static __always_inline ssize_t mfill_atomic_pte(struct mm_struct *dst_mm, 469 pmd_t *dst_pmd, 470 struct vm_area_struct *dst_vma, 471 unsigned long dst_addr, 472 unsigned long src_addr, 473 struct page **page, 474 enum mcopy_atomic_mode mode, 475 bool wp_copy) 476 { 477 ssize_t err; 478 479 if (mode == MCOPY_ATOMIC_CONTINUE) { 480 return mcontinue_atomic_pte(dst_mm, dst_pmd, dst_vma, dst_addr, 481 wp_copy); 482 } 483 484 /* 485 * The normal page fault path for a shmem will invoke the 486 * fault, fill the hole in the file and COW it right away. The 487 * result generates plain anonymous memory. So when we are 488 * asked to fill an hole in a MAP_PRIVATE shmem mapping, we'll 489 * generate anonymous memory directly without actually filling 490 * the hole. For the MAP_PRIVATE case the robustness check 491 * only happens in the pagetable (to verify it's still none) 492 * and not in the radix tree. 493 */ 494 if (!(dst_vma->vm_flags & VM_SHARED)) { 495 if (mode == MCOPY_ATOMIC_NORMAL) 496 err = mcopy_atomic_pte(dst_mm, dst_pmd, dst_vma, 497 dst_addr, src_addr, page, 498 wp_copy); 499 else 500 err = mfill_zeropage_pte(dst_mm, dst_pmd, 501 dst_vma, dst_addr); 502 } else { 503 err = shmem_mfill_atomic_pte(dst_mm, dst_pmd, dst_vma, 504 dst_addr, src_addr, 505 mode != MCOPY_ATOMIC_NORMAL, 506 wp_copy, page); 507 } 508 509 return err; 510 } 511 512 static __always_inline ssize_t __mcopy_atomic(struct mm_struct *dst_mm, 513 unsigned long dst_start, 514 unsigned long src_start, 515 unsigned long len, 516 enum mcopy_atomic_mode mcopy_mode, 517 atomic_t *mmap_changing, 518 __u64 mode) 519 { 520 struct vm_area_struct *dst_vma; 521 ssize_t err; 522 pmd_t *dst_pmd; 523 unsigned long src_addr, dst_addr; 524 long copied; 525 struct page *page; 526 bool wp_copy; 527 528 /* 529 * Sanitize the command parameters: 530 */ 531 BUG_ON(dst_start & ~PAGE_MASK); 532 BUG_ON(len & ~PAGE_MASK); 533 534 /* Does the address range wrap, or is the span zero-sized? */ 535 BUG_ON(src_start + len <= src_start); 536 BUG_ON(dst_start + len <= dst_start); 537 538 src_addr = src_start; 539 dst_addr = dst_start; 540 copied = 0; 541 page = NULL; 542 retry: 543 mmap_read_lock(dst_mm); 544 545 /* 546 * If memory mappings are changing because of non-cooperative 547 * operation (e.g. mremap) running in parallel, bail out and 548 * request the user to retry later 549 */ 550 err = -EAGAIN; 551 if (mmap_changing && atomic_read(mmap_changing)) 552 goto out_unlock; 553 554 /* 555 * Make sure the vma is not shared, that the dst range is 556 * both valid and fully within a single existing vma. 557 */ 558 err = -ENOENT; 559 dst_vma = find_dst_vma(dst_mm, dst_start, len); 560 if (!dst_vma) 561 goto out_unlock; 562 563 err = -EINVAL; 564 /* 565 * shmem_zero_setup is invoked in mmap for MAP_ANONYMOUS|MAP_SHARED but 566 * it will overwrite vm_ops, so vma_is_anonymous must return false. 567 */ 568 if (WARN_ON_ONCE(vma_is_anonymous(dst_vma) && 569 dst_vma->vm_flags & VM_SHARED)) 570 goto out_unlock; 571 572 /* 573 * validate 'mode' now that we know the dst_vma: don't allow 574 * a wrprotect copy if the userfaultfd didn't register as WP. 575 */ 576 wp_copy = mode & UFFDIO_COPY_MODE_WP; 577 if (wp_copy && !(dst_vma->vm_flags & VM_UFFD_WP)) 578 goto out_unlock; 579 580 /* 581 * If this is a HUGETLB vma, pass off to appropriate routine 582 */ 583 if (is_vm_hugetlb_page(dst_vma)) 584 return __mcopy_atomic_hugetlb(dst_mm, dst_vma, dst_start, 585 src_start, len, mcopy_mode, 586 wp_copy); 587 588 if (!vma_is_anonymous(dst_vma) && !vma_is_shmem(dst_vma)) 589 goto out_unlock; 590 if (!vma_is_shmem(dst_vma) && mcopy_mode == MCOPY_ATOMIC_CONTINUE) 591 goto out_unlock; 592 593 /* 594 * Ensure the dst_vma has a anon_vma or this page 595 * would get a NULL anon_vma when moved in the 596 * dst_vma. 597 */ 598 err = -ENOMEM; 599 if (!(dst_vma->vm_flags & VM_SHARED) && 600 unlikely(anon_vma_prepare(dst_vma))) 601 goto out_unlock; 602 603 while (src_addr < src_start + len) { 604 pmd_t dst_pmdval; 605 606 BUG_ON(dst_addr >= dst_start + len); 607 608 dst_pmd = mm_alloc_pmd(dst_mm, dst_addr); 609 if (unlikely(!dst_pmd)) { 610 err = -ENOMEM; 611 break; 612 } 613 614 dst_pmdval = pmd_read_atomic(dst_pmd); 615 /* 616 * If the dst_pmd is mapped as THP don't 617 * override it and just be strict. 618 */ 619 if (unlikely(pmd_trans_huge(dst_pmdval))) { 620 err = -EEXIST; 621 break; 622 } 623 if (unlikely(pmd_none(dst_pmdval)) && 624 unlikely(__pte_alloc(dst_mm, dst_pmd))) { 625 err = -ENOMEM; 626 break; 627 } 628 /* If an huge pmd materialized from under us fail */ 629 if (unlikely(pmd_trans_huge(*dst_pmd))) { 630 err = -EFAULT; 631 break; 632 } 633 634 BUG_ON(pmd_none(*dst_pmd)); 635 BUG_ON(pmd_trans_huge(*dst_pmd)); 636 637 err = mfill_atomic_pte(dst_mm, dst_pmd, dst_vma, dst_addr, 638 src_addr, &page, mcopy_mode, wp_copy); 639 cond_resched(); 640 641 if (unlikely(err == -ENOENT)) { 642 void *page_kaddr; 643 644 mmap_read_unlock(dst_mm); 645 BUG_ON(!page); 646 647 page_kaddr = kmap(page); 648 err = copy_from_user(page_kaddr, 649 (const void __user *) src_addr, 650 PAGE_SIZE); 651 kunmap(page); 652 if (unlikely(err)) { 653 err = -EFAULT; 654 goto out; 655 } 656 flush_dcache_page(page); 657 goto retry; 658 } else 659 BUG_ON(page); 660 661 if (!err) { 662 dst_addr += PAGE_SIZE; 663 src_addr += PAGE_SIZE; 664 copied += PAGE_SIZE; 665 666 if (fatal_signal_pending(current)) 667 err = -EINTR; 668 } 669 if (err) 670 break; 671 } 672 673 out_unlock: 674 mmap_read_unlock(dst_mm); 675 out: 676 if (page) 677 put_page(page); 678 BUG_ON(copied < 0); 679 BUG_ON(err > 0); 680 BUG_ON(!copied && !err); 681 return copied ? copied : err; 682 } 683 684 ssize_t mcopy_atomic(struct mm_struct *dst_mm, unsigned long dst_start, 685 unsigned long src_start, unsigned long len, 686 atomic_t *mmap_changing, __u64 mode) 687 { 688 return __mcopy_atomic(dst_mm, dst_start, src_start, len, 689 MCOPY_ATOMIC_NORMAL, mmap_changing, mode); 690 } 691 692 ssize_t mfill_zeropage(struct mm_struct *dst_mm, unsigned long start, 693 unsigned long len, atomic_t *mmap_changing) 694 { 695 return __mcopy_atomic(dst_mm, start, 0, len, MCOPY_ATOMIC_ZEROPAGE, 696 mmap_changing, 0); 697 } 698 699 ssize_t mcopy_continue(struct mm_struct *dst_mm, unsigned long start, 700 unsigned long len, atomic_t *mmap_changing) 701 { 702 return __mcopy_atomic(dst_mm, start, 0, len, MCOPY_ATOMIC_CONTINUE, 703 mmap_changing, 0); 704 } 705 706 int mwriteprotect_range(struct mm_struct *dst_mm, unsigned long start, 707 unsigned long len, bool enable_wp, 708 atomic_t *mmap_changing) 709 { 710 struct vm_area_struct *dst_vma; 711 unsigned long page_mask; 712 struct mmu_gather tlb; 713 pgprot_t newprot; 714 int err; 715 716 /* 717 * Sanitize the command parameters: 718 */ 719 BUG_ON(start & ~PAGE_MASK); 720 BUG_ON(len & ~PAGE_MASK); 721 722 /* Does the address range wrap, or is the span zero-sized? */ 723 BUG_ON(start + len <= start); 724 725 mmap_read_lock(dst_mm); 726 727 /* 728 * If memory mappings are changing because of non-cooperative 729 * operation (e.g. mremap) running in parallel, bail out and 730 * request the user to retry later 731 */ 732 err = -EAGAIN; 733 if (mmap_changing && atomic_read(mmap_changing)) 734 goto out_unlock; 735 736 err = -ENOENT; 737 dst_vma = find_dst_vma(dst_mm, start, len); 738 739 if (!dst_vma) 740 goto out_unlock; 741 if (!userfaultfd_wp(dst_vma)) 742 goto out_unlock; 743 if (!vma_can_userfault(dst_vma, dst_vma->vm_flags)) 744 goto out_unlock; 745 746 if (is_vm_hugetlb_page(dst_vma)) { 747 err = -EINVAL; 748 page_mask = vma_kernel_pagesize(dst_vma) - 1; 749 if ((start & page_mask) || (len & page_mask)) 750 goto out_unlock; 751 } 752 753 if (enable_wp) 754 newprot = vm_get_page_prot(dst_vma->vm_flags & ~(VM_WRITE)); 755 else 756 newprot = vm_get_page_prot(dst_vma->vm_flags); 757 758 tlb_gather_mmu(&tlb, dst_mm); 759 change_protection(&tlb, dst_vma, start, start + len, newprot, 760 enable_wp ? MM_CP_UFFD_WP : MM_CP_UFFD_WP_RESOLVE); 761 tlb_finish_mmu(&tlb); 762 763 err = 0; 764 out_unlock: 765 mmap_read_unlock(dst_mm); 766 return err; 767 } 768