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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
21static __always_inline
22struct 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 */
57int 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;
118out_unlock:
119 pte_unmap_unlock(dst_pte, ptl);
120 return ret;
121}
122
123static 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, 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;
174out:
175 return ret;
176out_release:
177 put_page(page);
178 goto out;
179}
180
181static 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;
211out_unlock:
212 pte_unmap_unlock(dst_pte, ptl);
213 return ret;
214}
215
216/* Handles UFFDIO_CONTINUE for all shmem VMAs (shared or private). */
217static 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;
243out:
244 return ret;
245out_release:
246 unlock_page(page);
247 put_page(page);
248 goto out;
249}
250
251static 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 */
277static __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
319retry:
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
416out_unlock:
417 mmap_read_unlock(dst_mm);
418out:
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 */
428extern 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
436static __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
481static __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 bool *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;
511retry:
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 && READ_ONCE(*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
640out_unlock:
641 mmap_read_unlock(dst_mm);
642out:
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
651ssize_t mcopy_atomic(struct mm_struct *dst_mm, unsigned long dst_start,
652 unsigned long src_start, unsigned long len,
653 bool *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
659ssize_t mfill_zeropage(struct mm_struct *dst_mm, unsigned long start,
660 unsigned long len, bool *mmap_changing)
661{
662 return __mcopy_atomic(dst_mm, start, 0, len, MCOPY_ATOMIC_ZEROPAGE,
663 mmap_changing, 0);
664}
665
666ssize_t mcopy_continue(struct mm_struct *dst_mm, unsigned long start,
667 unsigned long len, bool *mmap_changing)
668{
669 return __mcopy_atomic(dst_mm, start, 0, len, MCOPY_ATOMIC_CONTINUE,
670 mmap_changing, 0);
671}
672
673int mwriteprotect_range(struct mm_struct *dst_mm, unsigned long start,
674 unsigned long len, bool enable_wp, bool *mmap_changing)
675{
676 struct vm_area_struct *dst_vma;
677 pgprot_t newprot;
678 int err;
679
680 /*
681 * Sanitize the command parameters:
682 */
683 BUG_ON(start & ~PAGE_MASK);
684 BUG_ON(len & ~PAGE_MASK);
685
686 /* Does the address range wrap, or is the span zero-sized? */
687 BUG_ON(start + len <= start);
688
689 mmap_read_lock(dst_mm);
690
691 /*
692 * If memory mappings are changing because of non-cooperative
693 * operation (e.g. mremap) running in parallel, bail out and
694 * request the user to retry later
695 */
696 err = -EAGAIN;
697 if (mmap_changing && READ_ONCE(*mmap_changing))
698 goto out_unlock;
699
700 err = -ENOENT;
701 dst_vma = find_dst_vma(dst_mm, start, len);
702 /*
703 * Make sure the vma is not shared, that the dst range is
704 * both valid and fully within a single existing vma.
705 */
706 if (!dst_vma || (dst_vma->vm_flags & VM_SHARED))
707 goto out_unlock;
708 if (!userfaultfd_wp(dst_vma))
709 goto out_unlock;
710 if (!vma_is_anonymous(dst_vma))
711 goto out_unlock;
712
713 if (enable_wp)
714 newprot = vm_get_page_prot(dst_vma->vm_flags & ~(VM_WRITE));
715 else
716 newprot = vm_get_page_prot(dst_vma->vm_flags);
717
718 change_protection(dst_vma, start, start + len, newprot,
719 enable_wp ? MM_CP_UFFD_WP : MM_CP_UFFD_WP_RESOLVE);
720
721 err = 0;
722out_unlock:
723 mmap_read_unlock(dst_mm);
724 return err;
725}