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