?  search:
summary | log | graphiclog1 | graphiclog2 | commit | commitdiff | tree | refs | edit | fork
blame | history | raw | HEAD
Merge tag 'trace-printf-v6.13' of git://git.kernel.org/pub/scm/linux/kernel/git/trace...
[drm/drm-misc.git] / mm / userfaultfd.c
blob60a0be33766ffd71dd7de01d4b1f8fb71db98893
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 bool validate_dst_vma(struct vm_area_struct *dst_vma, unsigned long dst_end)
24 {
25 /* Make sure that the dst range is fully within dst_vma. */
26 if (dst_end > dst_vma->vm_end)
27 return false;
28
29 /*
30 * Check the vma is registered in uffd, this is required to
31 * enforce the VM_MAYWRITE check done at uffd registration
32 * time.
33 */
34 if (!dst_vma->vm_userfaultfd_ctx.ctx)
35 return false;
36
37 return true;
38 }
39
40 static __always_inline
41 struct vm_area_struct *find_vma_and_prepare_anon(struct mm_struct *mm,
42 unsigned long addr)
43 {
44 struct vm_area_struct *vma;
45
46 mmap_assert_locked(mm);
47 vma = vma_lookup(mm, addr);
48 if (!vma)
49 vma = ERR_PTR(-ENOENT);
50 else if (!(vma->vm_flags & VM_SHARED) &&
51 unlikely(anon_vma_prepare(vma)))
52 vma = ERR_PTR(-ENOMEM);
53
54 return vma;
55 }
56
57 #ifdef CONFIG_PER_VMA_LOCK
58 /*
59 * uffd_lock_vma() - Lookup and lock vma corresponding to @address.
60 * @mm: mm to search vma in.
61 * @address: address that the vma should contain.
62 *
63 * Should be called without holding mmap_lock.
64 *
65 * Return: A locked vma containing @address, -ENOENT if no vma is found, or
66 * -ENOMEM if anon_vma couldn't be allocated.
67 */
68 static struct vm_area_struct *uffd_lock_vma(struct mm_struct *mm,
69 unsigned long address)
70 {
71 struct vm_area_struct *vma;
72
73 vma = lock_vma_under_rcu(mm, address);
74 if (vma) {
75 /*
76 * We know we're going to need to use anon_vma, so check
77 * that early.
78 */
79 if (!(vma->vm_flags & VM_SHARED) && unlikely(!vma->anon_vma))
80 vma_end_read(vma);
81 else
82 return vma;
83 }
84
85 mmap_read_lock(mm);
86 vma = find_vma_and_prepare_anon(mm, address);
87 if (!IS_ERR(vma)) {
88 /*
89 * We cannot use vma_start_read() as it may fail due to
90 * false locked (see comment in vma_start_read()). We
91 * can avoid that by directly locking vm_lock under
92 * mmap_lock, which guarantees that nobody can lock the
93 * vma for write (vma_start_write()) under us.
94 */
95 down_read(&vma->vm_lock->lock);
96 }
97
98 mmap_read_unlock(mm);
99 return vma;
100 }
101
102 static struct vm_area_struct *uffd_mfill_lock(struct mm_struct *dst_mm,
103 unsigned long dst_start,
104 unsigned long len)
105 {
106 struct vm_area_struct *dst_vma;
107
108 dst_vma = uffd_lock_vma(dst_mm, dst_start);
109 if (IS_ERR(dst_vma) || validate_dst_vma(dst_vma, dst_start + len))
110 return dst_vma;
111
112 vma_end_read(dst_vma);
113 return ERR_PTR(-ENOENT);
114 }
115
116 static void uffd_mfill_unlock(struct vm_area_struct *vma)
117 {
118 vma_end_read(vma);
119 }
120
121 #else
122
123 static struct vm_area_struct *uffd_mfill_lock(struct mm_struct *dst_mm,
124 unsigned long dst_start,
125 unsigned long len)
126 {
127 struct vm_area_struct *dst_vma;
128
129 mmap_read_lock(dst_mm);
130 dst_vma = find_vma_and_prepare_anon(dst_mm, dst_start);
131 if (IS_ERR(dst_vma))
132 goto out_unlock;
133
134 if (validate_dst_vma(dst_vma, dst_start + len))
135 return dst_vma;
136
137 dst_vma = ERR_PTR(-ENOENT);
138 out_unlock:
139 mmap_read_unlock(dst_mm);
140 return dst_vma;
141 }
142
143 static void uffd_mfill_unlock(struct vm_area_struct *vma)
144 {
145 mmap_read_unlock(vma->vm_mm);
146 }
147 #endif
148
149 /* Check if dst_addr is outside of file's size. Must be called with ptl held. */
150 static bool mfill_file_over_size(struct vm_area_struct *dst_vma,
151 unsigned long dst_addr)
152 {
153 struct inode *inode;
154 pgoff_t offset, max_off;
155
156 if (!dst_vma->vm_file)
157 return false;
158
159 inode = dst_vma->vm_file->f_inode;
160 offset = linear_page_index(dst_vma, dst_addr);
161 max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
162 return offset >= max_off;
163 }
164
165 /*
166 * Install PTEs, to map dst_addr (within dst_vma) to page.
167 *
168 * This function handles both MCOPY_ATOMIC_NORMAL and _CONTINUE for both shmem
169 * and anon, and for both shared and private VMAs.
170 */
171 int mfill_atomic_install_pte(pmd_t *dst_pmd,
172 struct vm_area_struct *dst_vma,
173 unsigned long dst_addr, struct page *page,
174 bool newly_allocated, uffd_flags_t flags)
175 {
176 int ret;
177 struct mm_struct *dst_mm = dst_vma->vm_mm;
178 pte_t _dst_pte, *dst_pte;
179 bool writable = dst_vma->vm_flags & VM_WRITE;
180 bool vm_shared = dst_vma->vm_flags & VM_SHARED;
181 spinlock_t *ptl;
182 struct folio *folio = page_folio(page);
183 bool page_in_cache = folio_mapping(folio);
184
185 _dst_pte = mk_pte(page, dst_vma->vm_page_prot);
186 _dst_pte = pte_mkdirty(_dst_pte);
187 if (page_in_cache && !vm_shared)
188 writable = false;
189 if (writable)
190 _dst_pte = pte_mkwrite(_dst_pte, dst_vma);
191 if (flags & MFILL_ATOMIC_WP)
192 _dst_pte = pte_mkuffd_wp(_dst_pte);
193
194 ret = -EAGAIN;
195 dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl);
196 if (!dst_pte)
197 goto out;
198
199 if (mfill_file_over_size(dst_vma, dst_addr)) {
200 ret = -EFAULT;
201 goto out_unlock;
202 }
203
204 ret = -EEXIST;
205 /*
206 * We allow to overwrite a pte marker: consider when both MISSING|WP
207 * registered, we firstly wr-protect a none pte which has no page cache
208 * page backing it, then access the page.
209 */
210 if (!pte_none_mostly(ptep_get(dst_pte)))
211 goto out_unlock;
212
213 if (page_in_cache) {
214 /* Usually, cache pages are already added to LRU */
215 if (newly_allocated)
216 folio_add_lru(folio);
217 folio_add_file_rmap_pte(folio, page, dst_vma);
218 } else {
219 folio_add_new_anon_rmap(folio, dst_vma, dst_addr, RMAP_EXCLUSIVE);
220 folio_add_lru_vma(folio, dst_vma);
221 }
222
223 /*
224 * Must happen after rmap, as mm_counter() checks mapping (via
225 * PageAnon()), which is set by __page_set_anon_rmap().
226 */
227 inc_mm_counter(dst_mm, mm_counter(folio));
228
229 set_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte);
230
231 /* No need to invalidate - it was non-present before */
232 update_mmu_cache(dst_vma, dst_addr, dst_pte);
233 ret = 0;
234 out_unlock:
235 pte_unmap_unlock(dst_pte, ptl);
236 out:
237 return ret;
238 }
239
240 static int mfill_atomic_pte_copy(pmd_t *dst_pmd,
241 struct vm_area_struct *dst_vma,
242 unsigned long dst_addr,
243 unsigned long src_addr,
244 uffd_flags_t flags,
245 struct folio **foliop)
246 {
247 void *kaddr;
248 int ret;
249 struct folio *folio;
250
251 if (!*foliop) {
252 ret = -ENOMEM;
253 folio = vma_alloc_folio(GFP_HIGHUSER_MOVABLE, 0, dst_vma,
254 dst_addr);
255 if (!folio)
256 goto out;
257
258 kaddr = kmap_local_folio(folio, 0);
259 /*
260 * The read mmap_lock is held here. Despite the
261 * mmap_lock being read recursive a deadlock is still
262 * possible if a writer has taken a lock. For example:
263 *
264 * process A thread 1 takes read lock on own mmap_lock
265 * process A thread 2 calls mmap, blocks taking write lock
266 * process B thread 1 takes page fault, read lock on own mmap lock
267 * process B thread 2 calls mmap, blocks taking write lock
268 * process A thread 1 blocks taking read lock on process B
269 * process B thread 1 blocks taking read lock on process A
270 *
271 * Disable page faults to prevent potential deadlock
272 * and retry the copy outside the mmap_lock.
273 */
274 pagefault_disable();
275 ret = copy_from_user(kaddr, (const void __user *) src_addr,
276 PAGE_SIZE);
277 pagefault_enable();
278 kunmap_local(kaddr);
279
280 /* fallback to copy_from_user outside mmap_lock */
281 if (unlikely(ret)) {
282 ret = -ENOENT;
283 *foliop = folio;
284 /* don't free the page */
285 goto out;
286 }
287
288 flush_dcache_folio(folio);
289 } else {
290 folio = *foliop;
291 *foliop = NULL;
292 }
293
294 /*
295 * The memory barrier inside __folio_mark_uptodate makes sure that
296 * preceding stores to the page contents become visible before
297 * the set_pte_at() write.
298 */
299 __folio_mark_uptodate(folio);
300
301 ret = -ENOMEM;
302 if (mem_cgroup_charge(folio, dst_vma->vm_mm, GFP_KERNEL))
303 goto out_release;
304
305 ret = mfill_atomic_install_pte(dst_pmd, dst_vma, dst_addr,
306 &folio->page, true, flags);
307 if (ret)
308 goto out_release;
309 out:
310 return ret;
311 out_release:
312 folio_put(folio);
313 goto out;
314 }
315
316 static int mfill_atomic_pte_zeroed_folio(pmd_t *dst_pmd,
317 struct vm_area_struct *dst_vma,
318 unsigned long dst_addr)
319 {
320 struct folio *folio;
321 int ret = -ENOMEM;
322
323 folio = vma_alloc_zeroed_movable_folio(dst_vma, dst_addr);
324 if (!folio)
325 return ret;
326
327 if (mem_cgroup_charge(folio, dst_vma->vm_mm, GFP_KERNEL))
328 goto out_put;
329
330 /*
331 * The memory barrier inside __folio_mark_uptodate makes sure that
332 * zeroing out the folio become visible before mapping the page
333 * using set_pte_at(). See do_anonymous_page().
334 */
335 __folio_mark_uptodate(folio);
336
337 ret = mfill_atomic_install_pte(dst_pmd, dst_vma, dst_addr,
338 &folio->page, true, 0);
339 if (ret)
340 goto out_put;
341
342 return 0;
343 out_put:
344 folio_put(folio);
345 return ret;
346 }
347
348 static int mfill_atomic_pte_zeropage(pmd_t *dst_pmd,
349 struct vm_area_struct *dst_vma,
350 unsigned long dst_addr)
351 {
352 pte_t _dst_pte, *dst_pte;
353 spinlock_t *ptl;
354 int ret;
355
356 if (mm_forbids_zeropage(dst_vma->vm_mm))
357 return mfill_atomic_pte_zeroed_folio(dst_pmd, dst_vma, dst_addr);
358
359 _dst_pte = pte_mkspecial(pfn_pte(my_zero_pfn(dst_addr),
360 dst_vma->vm_page_prot));
361 ret = -EAGAIN;
362 dst_pte = pte_offset_map_lock(dst_vma->vm_mm, dst_pmd, dst_addr, &ptl);
363 if (!dst_pte)
364 goto out;
365 if (mfill_file_over_size(dst_vma, dst_addr)) {
366 ret = -EFAULT;
367 goto out_unlock;
368 }
369 ret = -EEXIST;
370 if (!pte_none(ptep_get(dst_pte)))
371 goto out_unlock;
372 set_pte_at(dst_vma->vm_mm, dst_addr, dst_pte, _dst_pte);
373 /* No need to invalidate - it was non-present before */
374 update_mmu_cache(dst_vma, dst_addr, dst_pte);
375 ret = 0;
376 out_unlock:
377 pte_unmap_unlock(dst_pte, ptl);
378 out:
379 return ret;
380 }
381
382 /* Handles UFFDIO_CONTINUE for all shmem VMAs (shared or private). */
383 static int mfill_atomic_pte_continue(pmd_t *dst_pmd,
384 struct vm_area_struct *dst_vma,
385 unsigned long dst_addr,
386 uffd_flags_t flags)
387 {
388 struct inode *inode = file_inode(dst_vma->vm_file);
389 pgoff_t pgoff = linear_page_index(dst_vma, dst_addr);
390 struct folio *folio;
391 struct page *page;
392 int ret;
393
394 ret = shmem_get_folio(inode, pgoff, 0, &folio, SGP_NOALLOC);
395 /* Our caller expects us to return -EFAULT if we failed to find folio */
396 if (ret == -ENOENT)
397 ret = -EFAULT;
398 if (ret)
399 goto out;
400 if (!folio) {
401 ret = -EFAULT;
402 goto out;
403 }
404
405 page = folio_file_page(folio, pgoff);
406 if (PageHWPoison(page)) {
407 ret = -EIO;
408 goto out_release;
409 }
410
411 ret = mfill_atomic_install_pte(dst_pmd, dst_vma, dst_addr,
412 page, false, flags);
413 if (ret)
414 goto out_release;
415
416 folio_unlock(folio);
417 ret = 0;
418 out:
419 return ret;
420 out_release:
421 folio_unlock(folio);
422 folio_put(folio);
423 goto out;
424 }
425
426 /* Handles UFFDIO_POISON for all non-hugetlb VMAs. */
427 static int mfill_atomic_pte_poison(pmd_t *dst_pmd,
428 struct vm_area_struct *dst_vma,
429 unsigned long dst_addr,
430 uffd_flags_t flags)
431 {
432 int ret;
433 struct mm_struct *dst_mm = dst_vma->vm_mm;
434 pte_t _dst_pte, *dst_pte;
435 spinlock_t *ptl;
436
437 _dst_pte = make_pte_marker(PTE_MARKER_POISONED);
438 ret = -EAGAIN;
439 dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl);
440 if (!dst_pte)
441 goto out;
442
443 if (mfill_file_over_size(dst_vma, dst_addr)) {
444 ret = -EFAULT;
445 goto out_unlock;
446 }
447
448 ret = -EEXIST;
449 /* Refuse to overwrite any PTE, even a PTE marker (e.g. UFFD WP). */
450 if (!pte_none(ptep_get(dst_pte)))
451 goto out_unlock;
452
453 set_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte);
454
455 /* No need to invalidate - it was non-present before */
456 update_mmu_cache(dst_vma, dst_addr, dst_pte);
457 ret = 0;
458 out_unlock:
459 pte_unmap_unlock(dst_pte, ptl);
460 out:
461 return ret;
462 }
463
464 static pmd_t *mm_alloc_pmd(struct mm_struct *mm, unsigned long address)
465 {
466 pgd_t *pgd;
467 p4d_t *p4d;
468 pud_t *pud;
469
470 pgd = pgd_offset(mm, address);
471 p4d = p4d_alloc(mm, pgd, address);
472 if (!p4d)
473 return NULL;
474 pud = pud_alloc(mm, p4d, address);
475 if (!pud)
476 return NULL;
477 /*
478 * Note that we didn't run this because the pmd was
479 * missing, the *pmd may be already established and in
480 * turn it may also be a trans_huge_pmd.
481 */
482 return pmd_alloc(mm, pud, address);
483 }
484
485 #ifdef CONFIG_HUGETLB_PAGE
486 /*
487 * mfill_atomic processing for HUGETLB vmas. Note that this routine is
488 * called with either vma-lock or mmap_lock held, it will release the lock
489 * before returning.
490 */
491 static __always_inline ssize_t mfill_atomic_hugetlb(
492 struct userfaultfd_ctx *ctx,
493 struct vm_area_struct *dst_vma,
494 unsigned long dst_start,
495 unsigned long src_start,
496 unsigned long len,
497 uffd_flags_t flags)
498 {
499 struct mm_struct *dst_mm = dst_vma->vm_mm;
500 ssize_t err;
501 pte_t *dst_pte;
502 unsigned long src_addr, dst_addr;
503 long copied;
504 struct folio *folio;
505 unsigned long vma_hpagesize;
506 pgoff_t idx;
507 u32 hash;
508 struct address_space *mapping;
509
510 /*
511 * There is no default zero huge page for all huge page sizes as
512 * supported by hugetlb. A PMD_SIZE huge pages may exist as used
513 * by THP. Since we can not reliably insert a zero page, this
514 * feature is not supported.
515 */
516 if (uffd_flags_mode_is(flags, MFILL_ATOMIC_ZEROPAGE)) {
517 up_read(&ctx->map_changing_lock);
518 uffd_mfill_unlock(dst_vma);
519 return -EINVAL;
520 }
521
522 src_addr = src_start;
523 dst_addr = dst_start;
524 copied = 0;
525 folio = NULL;
526 vma_hpagesize = vma_kernel_pagesize(dst_vma);
527
528 /*
529 * Validate alignment based on huge page size
530 */
531 err = -EINVAL;
532 if (dst_start & (vma_hpagesize - 1) || len & (vma_hpagesize - 1))
533 goto out_unlock;
534
535 retry:
536 /*
537 * On routine entry dst_vma is set. If we had to drop mmap_lock and
538 * retry, dst_vma will be set to NULL and we must lookup again.
539 */
540 if (!dst_vma) {
541 dst_vma = uffd_mfill_lock(dst_mm, dst_start, len);
542 if (IS_ERR(dst_vma)) {
543 err = PTR_ERR(dst_vma);
544 goto out;
545 }
546
547 err = -ENOENT;
548 if (!is_vm_hugetlb_page(dst_vma))
549 goto out_unlock_vma;
550
551 err = -EINVAL;
552 if (vma_hpagesize != vma_kernel_pagesize(dst_vma))
553 goto out_unlock_vma;
554
555 /*
556 * If memory mappings are changing because of non-cooperative
557 * operation (e.g. mremap) running in parallel, bail out and
558 * request the user to retry later
559 */
560 down_read(&ctx->map_changing_lock);
561 err = -EAGAIN;
562 if (atomic_read(&ctx->mmap_changing))
563 goto out_unlock;
564 }
565
566 while (src_addr < src_start + len) {
567 BUG_ON(dst_addr >= dst_start + len);
568
569 /*
570 * Serialize via vma_lock and hugetlb_fault_mutex.
571 * vma_lock ensures the dst_pte remains valid even
572 * in the case of shared pmds. fault mutex prevents
573 * races with other faulting threads.
574 */
575 idx = linear_page_index(dst_vma, dst_addr);
576 mapping = dst_vma->vm_file->f_mapping;
577 hash = hugetlb_fault_mutex_hash(mapping, idx);
578 mutex_lock(&hugetlb_fault_mutex_table[hash]);
579 hugetlb_vma_lock_read(dst_vma);
580
581 err = -ENOMEM;
582 dst_pte = huge_pte_alloc(dst_mm, dst_vma, dst_addr, vma_hpagesize);
583 if (!dst_pte) {
584 hugetlb_vma_unlock_read(dst_vma);
585 mutex_unlock(&hugetlb_fault_mutex_table[hash]);
586 goto out_unlock;
587 }
588
589 if (!uffd_flags_mode_is(flags, MFILL_ATOMIC_CONTINUE) &&
590 !huge_pte_none_mostly(huge_ptep_get(dst_mm, dst_addr, dst_pte))) {
591 err = -EEXIST;
592 hugetlb_vma_unlock_read(dst_vma);
593 mutex_unlock(&hugetlb_fault_mutex_table[hash]);
594 goto out_unlock;
595 }
596
597 err = hugetlb_mfill_atomic_pte(dst_pte, dst_vma, dst_addr,
598 src_addr, flags, &folio);
599
600 hugetlb_vma_unlock_read(dst_vma);
601 mutex_unlock(&hugetlb_fault_mutex_table[hash]);
602
603 cond_resched();
604
605 if (unlikely(err == -ENOENT)) {
606 up_read(&ctx->map_changing_lock);
607 uffd_mfill_unlock(dst_vma);
608 BUG_ON(!folio);
609
610 err = copy_folio_from_user(folio,
611 (const void __user *)src_addr, true);
612 if (unlikely(err)) {
613 err = -EFAULT;
614 goto out;
615 }
616
617 dst_vma = NULL;
618 goto retry;
619 } else
620 BUG_ON(folio);
621
622 if (!err) {
623 dst_addr += vma_hpagesize;
624 src_addr += vma_hpagesize;
625 copied += vma_hpagesize;
626
627 if (fatal_signal_pending(current))
628 err = -EINTR;
629 }
630 if (err)
631 break;
632 }
633
634 out_unlock:
635 up_read(&ctx->map_changing_lock);
636 out_unlock_vma:
637 uffd_mfill_unlock(dst_vma);
638 out:
639 if (folio)
640 folio_put(folio);
641 BUG_ON(copied < 0);
642 BUG_ON(err > 0);
643 BUG_ON(!copied && !err);
644 return copied ? copied : err;
645 }
646 #else /* !CONFIG_HUGETLB_PAGE */
647 /* fail at build time if gcc attempts to use this */
648 extern ssize_t mfill_atomic_hugetlb(struct userfaultfd_ctx *ctx,
649 struct vm_area_struct *dst_vma,
650 unsigned long dst_start,
651 unsigned long src_start,
652 unsigned long len,
653 uffd_flags_t flags);
654 #endif /* CONFIG_HUGETLB_PAGE */
655
656 static __always_inline ssize_t mfill_atomic_pte(pmd_t *dst_pmd,
657 struct vm_area_struct *dst_vma,
658 unsigned long dst_addr,
659 unsigned long src_addr,
660 uffd_flags_t flags,
661 struct folio **foliop)
662 {
663 ssize_t err;
664
665 if (uffd_flags_mode_is(flags, MFILL_ATOMIC_CONTINUE)) {
666 return mfill_atomic_pte_continue(dst_pmd, dst_vma,
667 dst_addr, flags);
668 } else if (uffd_flags_mode_is(flags, MFILL_ATOMIC_POISON)) {
669 return mfill_atomic_pte_poison(dst_pmd, dst_vma,
670 dst_addr, flags);
671 }
672
673 /*
674 * The normal page fault path for a shmem will invoke the
675 * fault, fill the hole in the file and COW it right away. The
676 * result generates plain anonymous memory. So when we are
677 * asked to fill an hole in a MAP_PRIVATE shmem mapping, we'll
678 * generate anonymous memory directly without actually filling
679 * the hole. For the MAP_PRIVATE case the robustness check
680 * only happens in the pagetable (to verify it's still none)
681 * and not in the radix tree.
682 */
683 if (!(dst_vma->vm_flags & VM_SHARED)) {
684 if (uffd_flags_mode_is(flags, MFILL_ATOMIC_COPY))
685 err = mfill_atomic_pte_copy(dst_pmd, dst_vma,
686 dst_addr, src_addr,
687 flags, foliop);
688 else
689 err = mfill_atomic_pte_zeropage(dst_pmd,
690 dst_vma, dst_addr);
691 } else {
692 err = shmem_mfill_atomic_pte(dst_pmd, dst_vma,
693 dst_addr, src_addr,
694 flags, foliop);
695 }
696
697 return err;
698 }
699
700 static __always_inline ssize_t mfill_atomic(struct userfaultfd_ctx *ctx,
701 unsigned long dst_start,
702 unsigned long src_start,
703 unsigned long len,
704 uffd_flags_t flags)
705 {
706 struct mm_struct *dst_mm = ctx->mm;
707 struct vm_area_struct *dst_vma;
708 ssize_t err;
709 pmd_t *dst_pmd;
710 unsigned long src_addr, dst_addr;
711 long copied;
712 struct folio *folio;
713
714 /*
715 * Sanitize the command parameters:
716 */
717 BUG_ON(dst_start & ~PAGE_MASK);
718 BUG_ON(len & ~PAGE_MASK);
719
720 /* Does the address range wrap, or is the span zero-sized? */
721 BUG_ON(src_start + len <= src_start);
722 BUG_ON(dst_start + len <= dst_start);
723
724 src_addr = src_start;
725 dst_addr = dst_start;
726 copied = 0;
727 folio = NULL;
728 retry:
729 /*
730 * Make sure the vma is not shared, that the dst range is
731 * both valid and fully within a single existing vma.
732 */
733 dst_vma = uffd_mfill_lock(dst_mm, dst_start, len);
734 if (IS_ERR(dst_vma)) {
735 err = PTR_ERR(dst_vma);
736 goto out;
737 }
738
739 /*
740 * If memory mappings are changing because of non-cooperative
741 * operation (e.g. mremap) running in parallel, bail out and
742 * request the user to retry later
743 */
744 down_read(&ctx->map_changing_lock);
745 err = -EAGAIN;
746 if (atomic_read(&ctx->mmap_changing))
747 goto out_unlock;
748
749 err = -EINVAL;
750 /*
751 * shmem_zero_setup is invoked in mmap for MAP_ANONYMOUS|MAP_SHARED but
752 * it will overwrite vm_ops, so vma_is_anonymous must return false.
753 */
754 if (WARN_ON_ONCE(vma_is_anonymous(dst_vma) &&
755 dst_vma->vm_flags & VM_SHARED))
756 goto out_unlock;
757
758 /*
759 * validate 'mode' now that we know the dst_vma: don't allow
760 * a wrprotect copy if the userfaultfd didn't register as WP.
761 */
762 if ((flags & MFILL_ATOMIC_WP) && !(dst_vma->vm_flags & VM_UFFD_WP))
763 goto out_unlock;
764
765 /*
766 * If this is a HUGETLB vma, pass off to appropriate routine
767 */
768 if (is_vm_hugetlb_page(dst_vma))
769 return mfill_atomic_hugetlb(ctx, dst_vma, dst_start,
770 src_start, len, flags);
771
772 if (!vma_is_anonymous(dst_vma) && !vma_is_shmem(dst_vma))
773 goto out_unlock;
774 if (!vma_is_shmem(dst_vma) &&
775 uffd_flags_mode_is(flags, MFILL_ATOMIC_CONTINUE))
776 goto out_unlock;
777
778 while (src_addr < src_start + len) {
779 pmd_t dst_pmdval;
780
781 BUG_ON(dst_addr >= dst_start + len);
782
783 dst_pmd = mm_alloc_pmd(dst_mm, dst_addr);
784 if (unlikely(!dst_pmd)) {
785 err = -ENOMEM;
786 break;
787 }
788
789 dst_pmdval = pmdp_get_lockless(dst_pmd);
790 if (unlikely(pmd_none(dst_pmdval)) &&
791 unlikely(__pte_alloc(dst_mm, dst_pmd))) {
792 err = -ENOMEM;
793 break;
794 }
795 dst_pmdval = pmdp_get_lockless(dst_pmd);
796 /*
797 * If the dst_pmd is THP don't override it and just be strict.
798 * (This includes the case where the PMD used to be THP and
799 * changed back to none after __pte_alloc().)
800 */
801 if (unlikely(!pmd_present(dst_pmdval) || pmd_trans_huge(dst_pmdval) ||
802 pmd_devmap(dst_pmdval))) {
803 err = -EEXIST;
804 break;
805 }
806 if (unlikely(pmd_bad(dst_pmdval))) {
807 err = -EFAULT;
808 break;
809 }
810 /*
811 * For shmem mappings, khugepaged is allowed to remove page
812 * tables under us; pte_offset_map_lock() will deal with that.
813 */
814
815 err = mfill_atomic_pte(dst_pmd, dst_vma, dst_addr,
816 src_addr, flags, &folio);
817 cond_resched();
818
819 if (unlikely(err == -ENOENT)) {
820 void *kaddr;
821
822 up_read(&ctx->map_changing_lock);
823 uffd_mfill_unlock(dst_vma);
824 BUG_ON(!folio);
825
826 kaddr = kmap_local_folio(folio, 0);
827 err = copy_from_user(kaddr,
828 (const void __user *) src_addr,
829 PAGE_SIZE);
830 kunmap_local(kaddr);
831 if (unlikely(err)) {
832 err = -EFAULT;
833 goto out;
834 }
835 flush_dcache_folio(folio);
836 goto retry;
837 } else
838 BUG_ON(folio);
839
840 if (!err) {
841 dst_addr += PAGE_SIZE;
842 src_addr += PAGE_SIZE;
843 copied += PAGE_SIZE;
844
845 if (fatal_signal_pending(current))
846 err = -EINTR;
847 }
848 if (err)
849 break;
850 }
851
852 out_unlock:
853 up_read(&ctx->map_changing_lock);
854 uffd_mfill_unlock(dst_vma);
855 out:
856 if (folio)
857 folio_put(folio);
858 BUG_ON(copied < 0);
859 BUG_ON(err > 0);
860 BUG_ON(!copied && !err);
861 return copied ? copied : err;
862 }
863
864 ssize_t mfill_atomic_copy(struct userfaultfd_ctx *ctx, unsigned long dst_start,
865 unsigned long src_start, unsigned long len,
866 uffd_flags_t flags)
867 {
868 return mfill_atomic(ctx, dst_start, src_start, len,
869 uffd_flags_set_mode(flags, MFILL_ATOMIC_COPY));
870 }
871
872 ssize_t mfill_atomic_zeropage(struct userfaultfd_ctx *ctx,
873 unsigned long start,
874 unsigned long len)
875 {
876 return mfill_atomic(ctx, start, 0, len,
877 uffd_flags_set_mode(0, MFILL_ATOMIC_ZEROPAGE));
878 }
879
880 ssize_t mfill_atomic_continue(struct userfaultfd_ctx *ctx, unsigned long start,
881 unsigned long len, uffd_flags_t flags)
882 {
883
884 /*
885 * A caller might reasonably assume that UFFDIO_CONTINUE contains an
886 * smp_wmb() to ensure that any writes to the about-to-be-mapped page by
887 * the thread doing the UFFDIO_CONTINUE are guaranteed to be visible to
888 * subsequent loads from the page through the newly mapped address range.
889 */
890 smp_wmb();
891
892 return mfill_atomic(ctx, start, 0, len,
893 uffd_flags_set_mode(flags, MFILL_ATOMIC_CONTINUE));
894 }
895
896 ssize_t mfill_atomic_poison(struct userfaultfd_ctx *ctx, unsigned long start,
897 unsigned long len, uffd_flags_t flags)
898 {
899 return mfill_atomic(ctx, start, 0, len,
900 uffd_flags_set_mode(flags, MFILL_ATOMIC_POISON));
901 }
902
903 long uffd_wp_range(struct vm_area_struct *dst_vma,
904 unsigned long start, unsigned long len, bool enable_wp)
905 {
906 unsigned int mm_cp_flags;
907 struct mmu_gather tlb;
908 long ret;
909
910 VM_WARN_ONCE(start < dst_vma->vm_start || start + len > dst_vma->vm_end,
911 "The address range exceeds VMA boundary.\n");
912 if (enable_wp)
913 mm_cp_flags = MM_CP_UFFD_WP;
914 else
915 mm_cp_flags = MM_CP_UFFD_WP_RESOLVE;
916
917 /*
918 * vma->vm_page_prot already reflects that uffd-wp is enabled for this
919 * VMA (see userfaultfd_set_vm_flags()) and that all PTEs are supposed
920 * to be write-protected as default whenever protection changes.
921 * Try upgrading write permissions manually.
922 */
923 if (!enable_wp && vma_wants_manual_pte_write_upgrade(dst_vma))
924 mm_cp_flags |= MM_CP_TRY_CHANGE_WRITABLE;
925 tlb_gather_mmu(&tlb, dst_vma->vm_mm);
926 ret = change_protection(&tlb, dst_vma, start, start + len, mm_cp_flags);
927 tlb_finish_mmu(&tlb);
928
929 return ret;
930 }
931
932 int mwriteprotect_range(struct userfaultfd_ctx *ctx, unsigned long start,
933 unsigned long len, bool enable_wp)
934 {
935 struct mm_struct *dst_mm = ctx->mm;
936 unsigned long end = start + len;
937 unsigned long _start, _end;
938 struct vm_area_struct *dst_vma;
939 unsigned long page_mask;
940 long err;
941 VMA_ITERATOR(vmi, dst_mm, start);
942
943 /*
944 * Sanitize the command parameters:
945 */
946 BUG_ON(start & ~PAGE_MASK);
947 BUG_ON(len & ~PAGE_MASK);
948
949 /* Does the address range wrap, or is the span zero-sized? */
950 BUG_ON(start + len <= start);
951
952 mmap_read_lock(dst_mm);
953
954 /*
955 * If memory mappings are changing because of non-cooperative
956 * operation (e.g. mremap) running in parallel, bail out and
957 * request the user to retry later
958 */
959 down_read(&ctx->map_changing_lock);
960 err = -EAGAIN;
961 if (atomic_read(&ctx->mmap_changing))
962 goto out_unlock;
963
964 err = -ENOENT;
965 for_each_vma_range(vmi, dst_vma, end) {
966
967 if (!userfaultfd_wp(dst_vma)) {
968 err = -ENOENT;
969 break;
970 }
971
972 if (is_vm_hugetlb_page(dst_vma)) {
973 err = -EINVAL;
974 page_mask = vma_kernel_pagesize(dst_vma) - 1;
975 if ((start & page_mask) || (len & page_mask))
976 break;
977 }
978
979 _start = max(dst_vma->vm_start, start);
980 _end = min(dst_vma->vm_end, end);
981
982 err = uffd_wp_range(dst_vma, _start, _end - _start, enable_wp);
983
984 /* Return 0 on success, <0 on failures */
985 if (err < 0)
986 break;
987 err = 0;
988 }
989 out_unlock:
990 up_read(&ctx->map_changing_lock);
991 mmap_read_unlock(dst_mm);
992 return err;
993 }
994
995
996 void double_pt_lock(spinlock_t *ptl1,
997 spinlock_t *ptl2)
998 __acquires(ptl1)
999 __acquires(ptl2)
1000 {
1001 if (ptl1 > ptl2)
1002 swap(ptl1, ptl2);
1003 /* lock in virtual address order to avoid lock inversion */
1004 spin_lock(ptl1);
1005 if (ptl1 != ptl2)
1006 spin_lock_nested(ptl2, SINGLE_DEPTH_NESTING);
1007 else
1008 __acquire(ptl2);
1009 }
1010
1011 void double_pt_unlock(spinlock_t *ptl1,
1012 spinlock_t *ptl2)
1013 __releases(ptl1)
1014 __releases(ptl2)
1015 {
1016 spin_unlock(ptl1);
1017 if (ptl1 != ptl2)
1018 spin_unlock(ptl2);
1019 else
1020 __release(ptl2);
1021 }
1022
1023
1024 static int move_present_pte(struct mm_struct *mm,
1025 struct vm_area_struct *dst_vma,
1026 struct vm_area_struct *src_vma,
1027 unsigned long dst_addr, unsigned long src_addr,
1028 pte_t *dst_pte, pte_t *src_pte,
1029 pte_t orig_dst_pte, pte_t orig_src_pte,
1030 spinlock_t *dst_ptl, spinlock_t *src_ptl,
1031 struct folio *src_folio)
1032 {
1033 int err = 0;
1034
1035 double_pt_lock(dst_ptl, src_ptl);
1036
1037 if (!pte_same(ptep_get(src_pte), orig_src_pte) ||
1038 !pte_same(ptep_get(dst_pte), orig_dst_pte)) {
1039 err = -EAGAIN;
1040 goto out;
1041 }
1042 if (folio_test_large(src_folio) ||
1043 folio_maybe_dma_pinned(src_folio) ||
1044 !PageAnonExclusive(&src_folio->page)) {
1045 err = -EBUSY;
1046 goto out;
1047 }
1048
1049 orig_src_pte = ptep_clear_flush(src_vma, src_addr, src_pte);
1050 /* Folio got pinned from under us. Put it back and fail the move. */
1051 if (folio_maybe_dma_pinned(src_folio)) {
1052 set_pte_at(mm, src_addr, src_pte, orig_src_pte);
1053 err = -EBUSY;
1054 goto out;
1055 }
1056
1057 folio_move_anon_rmap(src_folio, dst_vma);
1058 src_folio->index = linear_page_index(dst_vma, dst_addr);
1059
1060 orig_dst_pte = mk_pte(&src_folio->page, dst_vma->vm_page_prot);
1061 /* Follow mremap() behavior and treat the entry dirty after the move */
1062 orig_dst_pte = pte_mkwrite(pte_mkdirty(orig_dst_pte), dst_vma);
1063
1064 set_pte_at(mm, dst_addr, dst_pte, orig_dst_pte);
1065 out:
1066 double_pt_unlock(dst_ptl, src_ptl);
1067 return err;
1068 }
1069
1070 static int move_swap_pte(struct mm_struct *mm,
1071 unsigned long dst_addr, unsigned long src_addr,
1072 pte_t *dst_pte, pte_t *src_pte,
1073 pte_t orig_dst_pte, pte_t orig_src_pte,
1074 spinlock_t *dst_ptl, spinlock_t *src_ptl)
1075 {
1076 if (!pte_swp_exclusive(orig_src_pte))
1077 return -EBUSY;
1078
1079 double_pt_lock(dst_ptl, src_ptl);
1080
1081 if (!pte_same(ptep_get(src_pte), orig_src_pte) ||
1082 !pte_same(ptep_get(dst_pte), orig_dst_pte)) {
1083 double_pt_unlock(dst_ptl, src_ptl);
1084 return -EAGAIN;
1085 }
1086
1087 orig_src_pte = ptep_get_and_clear(mm, src_addr, src_pte);
1088 set_pte_at(mm, dst_addr, dst_pte, orig_src_pte);
1089 double_pt_unlock(dst_ptl, src_ptl);
1090
1091 return 0;
1092 }
1093
1094 static int move_zeropage_pte(struct mm_struct *mm,
1095 struct vm_area_struct *dst_vma,
1096 struct vm_area_struct *src_vma,
1097 unsigned long dst_addr, unsigned long src_addr,
1098 pte_t *dst_pte, pte_t *src_pte,
1099 pte_t orig_dst_pte, pte_t orig_src_pte,
1100 spinlock_t *dst_ptl, spinlock_t *src_ptl)
1101 {
1102 pte_t zero_pte;
1103
1104 double_pt_lock(dst_ptl, src_ptl);
1105 if (!pte_same(ptep_get(src_pte), orig_src_pte) ||
1106 !pte_same(ptep_get(dst_pte), orig_dst_pte)) {
1107 double_pt_unlock(dst_ptl, src_ptl);
1108 return -EAGAIN;
1109 }
1110
1111 zero_pte = pte_mkspecial(pfn_pte(my_zero_pfn(dst_addr),
1112 dst_vma->vm_page_prot));
1113 ptep_clear_flush(src_vma, src_addr, src_pte);
1114 set_pte_at(mm, dst_addr, dst_pte, zero_pte);
1115 double_pt_unlock(dst_ptl, src_ptl);
1116
1117 return 0;
1118 }
1119
1120
1121 /*
1122 * The mmap_lock for reading is held by the caller. Just move the page
1123 * from src_pmd to dst_pmd if possible, and return true if succeeded
1124 * in moving the page.
1125 */
1126 static int move_pages_pte(struct mm_struct *mm, pmd_t *dst_pmd, pmd_t *src_pmd,
1127 struct vm_area_struct *dst_vma,
1128 struct vm_area_struct *src_vma,
1129 unsigned long dst_addr, unsigned long src_addr,
1130 __u64 mode)
1131 {
1132 swp_entry_t entry;
1133 pte_t orig_src_pte, orig_dst_pte;
1134 pte_t src_folio_pte;
1135 spinlock_t *src_ptl, *dst_ptl;
1136 pte_t *src_pte = NULL;
1137 pte_t *dst_pte = NULL;
1138 pmd_t dummy_pmdval;
1139 struct folio *src_folio = NULL;
1140 struct anon_vma *src_anon_vma = NULL;
1141 struct mmu_notifier_range range;
1142 int err = 0;
1143
1144 flush_cache_range(src_vma, src_addr, src_addr + PAGE_SIZE);
1145 mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, mm,
1146 src_addr, src_addr + PAGE_SIZE);
1147 mmu_notifier_invalidate_range_start(&range);
1148 retry:
1149 /*
1150 * Use the maywrite version to indicate that dst_pte will be modified,
1151 * but since we will use pte_same() to detect the change of the pte
1152 * entry, there is no need to get pmdval, so just pass a dummy variable
1153 * to it.
1154 */
1155 dst_pte = pte_offset_map_rw_nolock(mm, dst_pmd, dst_addr, &dummy_pmdval,
1156 &dst_ptl);
1157
1158 /* Retry if a huge pmd materialized from under us */
1159 if (unlikely(!dst_pte)) {
1160 err = -EAGAIN;
1161 goto out;
1162 }
1163
1164 /* same as dst_pte */
1165 src_pte = pte_offset_map_rw_nolock(mm, src_pmd, src_addr, &dummy_pmdval,
1166 &src_ptl);
1167
1168 /*
1169 * We held the mmap_lock for reading so MADV_DONTNEED
1170 * can zap transparent huge pages under us, or the
1171 * transparent huge page fault can establish new
1172 * transparent huge pages under us.
1173 */
1174 if (unlikely(!src_pte)) {
1175 err = -EAGAIN;
1176 goto out;
1177 }
1178
1179 /* Sanity checks before the operation */
1180 if (WARN_ON_ONCE(pmd_none(*dst_pmd)) || WARN_ON_ONCE(pmd_none(*src_pmd)) ||
1181 WARN_ON_ONCE(pmd_trans_huge(*dst_pmd)) || WARN_ON_ONCE(pmd_trans_huge(*src_pmd))) {
1182 err = -EINVAL;
1183 goto out;
1184 }
1185
1186 spin_lock(dst_ptl);
1187 orig_dst_pte = ptep_get(dst_pte);
1188 spin_unlock(dst_ptl);
1189 if (!pte_none(orig_dst_pte)) {
1190 err = -EEXIST;
1191 goto out;
1192 }
1193
1194 spin_lock(src_ptl);
1195 orig_src_pte = ptep_get(src_pte);
1196 spin_unlock(src_ptl);
1197 if (pte_none(orig_src_pte)) {
1198 if (!(mode & UFFDIO_MOVE_MODE_ALLOW_SRC_HOLES))
1199 err = -ENOENT;
1200 else /* nothing to do to move a hole */
1201 err = 0;
1202 goto out;
1203 }
1204
1205 /* If PTE changed after we locked the folio them start over */
1206 if (src_folio && unlikely(!pte_same(src_folio_pte, orig_src_pte))) {
1207 err = -EAGAIN;
1208 goto out;
1209 }
1210
1211 if (pte_present(orig_src_pte)) {
1212 if (is_zero_pfn(pte_pfn(orig_src_pte))) {
1213 err = move_zeropage_pte(mm, dst_vma, src_vma,
1214 dst_addr, src_addr, dst_pte, src_pte,
1215 orig_dst_pte, orig_src_pte,
1216 dst_ptl, src_ptl);
1217 goto out;
1218 }
1219
1220 /*
1221 * Pin and lock both source folio and anon_vma. Since we are in
1222 * RCU read section, we can't block, so on contention have to
1223 * unmap the ptes, obtain the lock and retry.
1224 */
1225 if (!src_folio) {
1226 struct folio *folio;
1227
1228 /*
1229 * Pin the page while holding the lock to be sure the
1230 * page isn't freed under us
1231 */
1232 spin_lock(src_ptl);
1233 if (!pte_same(orig_src_pte, ptep_get(src_pte))) {
1234 spin_unlock(src_ptl);
1235 err = -EAGAIN;
1236 goto out;
1237 }
1238
1239 folio = vm_normal_folio(src_vma, src_addr, orig_src_pte);
1240 if (!folio || !PageAnonExclusive(&folio->page)) {
1241 spin_unlock(src_ptl);
1242 err = -EBUSY;
1243 goto out;
1244 }
1245
1246 folio_get(folio);
1247 src_folio = folio;
1248 src_folio_pte = orig_src_pte;
1249 spin_unlock(src_ptl);
1250
1251 if (!folio_trylock(src_folio)) {
1252 pte_unmap(&orig_src_pte);
1253 pte_unmap(&orig_dst_pte);
1254 src_pte = dst_pte = NULL;
1255 /* now we can block and wait */
1256 folio_lock(src_folio);
1257 goto retry;
1258 }
1259
1260 if (WARN_ON_ONCE(!folio_test_anon(src_folio))) {
1261 err = -EBUSY;
1262 goto out;
1263 }
1264 }
1265
1266 /* at this point we have src_folio locked */
1267 if (folio_test_large(src_folio)) {
1268 /* split_folio() can block */
1269 pte_unmap(&orig_src_pte);
1270 pte_unmap(&orig_dst_pte);
1271 src_pte = dst_pte = NULL;
1272 err = split_folio(src_folio);
1273 if (err)
1274 goto out;
1275 /* have to reacquire the folio after it got split */
1276 folio_unlock(src_folio);
1277 folio_put(src_folio);
1278 src_folio = NULL;
1279 goto retry;
1280 }
1281
1282 if (!src_anon_vma) {
1283 /*
1284 * folio_referenced walks the anon_vma chain
1285 * without the folio lock. Serialize against it with
1286 * the anon_vma lock, the folio lock is not enough.
1287 */
1288 src_anon_vma = folio_get_anon_vma(src_folio);
1289 if (!src_anon_vma) {
1290 /* page was unmapped from under us */
1291 err = -EAGAIN;
1292 goto out;
1293 }
1294 if (!anon_vma_trylock_write(src_anon_vma)) {
1295 pte_unmap(&orig_src_pte);
1296 pte_unmap(&orig_dst_pte);
1297 src_pte = dst_pte = NULL;
1298 /* now we can block and wait */
1299 anon_vma_lock_write(src_anon_vma);
1300 goto retry;
1301 }
1302 }
1303
1304 err = move_present_pte(mm, dst_vma, src_vma,
1305 dst_addr, src_addr, dst_pte, src_pte,
1306 orig_dst_pte, orig_src_pte,
1307 dst_ptl, src_ptl, src_folio);
1308 } else {
1309 entry = pte_to_swp_entry(orig_src_pte);
1310 if (non_swap_entry(entry)) {
1311 if (is_migration_entry(entry)) {
1312 pte_unmap(&orig_src_pte);
1313 pte_unmap(&orig_dst_pte);
1314 src_pte = dst_pte = NULL;
1315 migration_entry_wait(mm, src_pmd, src_addr);
1316 err = -EAGAIN;
1317 } else
1318 err = -EFAULT;
1319 goto out;
1320 }
1321
1322 err = move_swap_pte(mm, dst_addr, src_addr,
1323 dst_pte, src_pte,
1324 orig_dst_pte, orig_src_pte,
1325 dst_ptl, src_ptl);
1326 }
1327
1328 out:
1329 if (src_anon_vma) {
1330 anon_vma_unlock_write(src_anon_vma);
1331 put_anon_vma(src_anon_vma);
1332 }
1333 if (src_folio) {
1334 folio_unlock(src_folio);
1335 folio_put(src_folio);
1336 }
1337 if (dst_pte)
1338 pte_unmap(dst_pte);
1339 if (src_pte)
1340 pte_unmap(src_pte);
1341 mmu_notifier_invalidate_range_end(&range);
1342
1343 return err;
1344 }
1345
1346 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
1347 static inline bool move_splits_huge_pmd(unsigned long dst_addr,
1348 unsigned long src_addr,
1349 unsigned long src_end)
1350 {
1351 return (src_addr & ~HPAGE_PMD_MASK) || (dst_addr & ~HPAGE_PMD_MASK) ||
1352 src_end - src_addr < HPAGE_PMD_SIZE;
1353 }
1354 #else
1355 static inline bool move_splits_huge_pmd(unsigned long dst_addr,
1356 unsigned long src_addr,
1357 unsigned long src_end)
1358 {
1359 /* This is unreachable anyway, just to avoid warnings when HPAGE_PMD_SIZE==0 */
1360 return false;
1361 }
1362 #endif
1363
1364 static inline bool vma_move_compatible(struct vm_area_struct *vma)
1365 {
1366 return !(vma->vm_flags & (VM_PFNMAP | VM_IO | VM_HUGETLB |
1367 VM_MIXEDMAP | VM_SHADOW_STACK));
1368 }
1369
1370 static int validate_move_areas(struct userfaultfd_ctx *ctx,
1371 struct vm_area_struct *src_vma,
1372 struct vm_area_struct *dst_vma)
1373 {
1374 /* Only allow moving if both have the same access and protection */
1375 if ((src_vma->vm_flags & VM_ACCESS_FLAGS) != (dst_vma->vm_flags & VM_ACCESS_FLAGS) ||
1376 pgprot_val(src_vma->vm_page_prot) != pgprot_val(dst_vma->vm_page_prot))
1377 return -EINVAL;
1378
1379 /* Only allow moving if both are mlocked or both aren't */
1380 if ((src_vma->vm_flags & VM_LOCKED) != (dst_vma->vm_flags & VM_LOCKED))
1381 return -EINVAL;
1382
1383 /*
1384 * For now, we keep it simple and only move between writable VMAs.
1385 * Access flags are equal, therefore cheching only the source is enough.
1386 */
1387 if (!(src_vma->vm_flags & VM_WRITE))
1388 return -EINVAL;
1389
1390 /* Check if vma flags indicate content which can be moved */
1391 if (!vma_move_compatible(src_vma) || !vma_move_compatible(dst_vma))
1392 return -EINVAL;
1393
1394 /* Ensure dst_vma is registered in uffd we are operating on */
1395 if (!dst_vma->vm_userfaultfd_ctx.ctx ||
1396 dst_vma->vm_userfaultfd_ctx.ctx != ctx)
1397 return -EINVAL;
1398
1399 /* Only allow moving across anonymous vmas */
1400 if (!vma_is_anonymous(src_vma) || !vma_is_anonymous(dst_vma))
1401 return -EINVAL;
1402
1403 return 0;
1404 }
1405
1406 static __always_inline
1407 int find_vmas_mm_locked(struct mm_struct *mm,
1408 unsigned long dst_start,
1409 unsigned long src_start,
1410 struct vm_area_struct **dst_vmap,
1411 struct vm_area_struct **src_vmap)
1412 {
1413 struct vm_area_struct *vma;
1414
1415 mmap_assert_locked(mm);
1416 vma = find_vma_and_prepare_anon(mm, dst_start);
1417 if (IS_ERR(vma))
1418 return PTR_ERR(vma);
1419
1420 *dst_vmap = vma;
1421 /* Skip finding src_vma if src_start is in dst_vma */
1422 if (src_start >= vma->vm_start && src_start < vma->vm_end)
1423 goto out_success;
1424
1425 vma = vma_lookup(mm, src_start);
1426 if (!vma)
1427 return -ENOENT;
1428 out_success:
1429 *src_vmap = vma;
1430 return 0;
1431 }
1432
1433 #ifdef CONFIG_PER_VMA_LOCK
1434 static int uffd_move_lock(struct mm_struct *mm,
1435 unsigned long dst_start,
1436 unsigned long src_start,
1437 struct vm_area_struct **dst_vmap,
1438 struct vm_area_struct **src_vmap)
1439 {
1440 struct vm_area_struct *vma;
1441 int err;
1442
1443 vma = uffd_lock_vma(mm, dst_start);
1444 if (IS_ERR(vma))
1445 return PTR_ERR(vma);
1446
1447 *dst_vmap = vma;
1448 /*
1449 * Skip finding src_vma if src_start is in dst_vma. This also ensures
1450 * that we don't lock the same vma twice.
1451 */
1452 if (src_start >= vma->vm_start && src_start < vma->vm_end) {
1453 *src_vmap = vma;
1454 return 0;
1455 }
1456
1457 /*
1458 * Using uffd_lock_vma() to get src_vma can lead to following deadlock:
1459 *
1460 * Thread1 Thread2
1461 * ------- -------
1462 * vma_start_read(dst_vma)
1463 * mmap_write_lock(mm)
1464 * vma_start_write(src_vma)
1465 * vma_start_read(src_vma)
1466 * mmap_read_lock(mm)
1467 * vma_start_write(dst_vma)
1468 */
1469 *src_vmap = lock_vma_under_rcu(mm, src_start);
1470 if (likely(*src_vmap))
1471 return 0;
1472
1473 /* Undo any locking and retry in mmap_lock critical section */
1474 vma_end_read(*dst_vmap);
1475
1476 mmap_read_lock(mm);
1477 err = find_vmas_mm_locked(mm, dst_start, src_start, dst_vmap, src_vmap);
1478 if (!err) {
1479 /*
1480 * See comment in uffd_lock_vma() as to why not using
1481 * vma_start_read() here.
1482 */
1483 down_read(&(*dst_vmap)->vm_lock->lock);
1484 if (*dst_vmap != *src_vmap)
1485 down_read_nested(&(*src_vmap)->vm_lock->lock,
1486 SINGLE_DEPTH_NESTING);
1487 }
1488 mmap_read_unlock(mm);
1489 return err;
1490 }
1491
1492 static void uffd_move_unlock(struct vm_area_struct *dst_vma,
1493 struct vm_area_struct *src_vma)
1494 {
1495 vma_end_read(src_vma);
1496 if (src_vma != dst_vma)
1497 vma_end_read(dst_vma);
1498 }
1499
1500 #else
1501
1502 static int uffd_move_lock(struct mm_struct *mm,
1503 unsigned long dst_start,
1504 unsigned long src_start,
1505 struct vm_area_struct **dst_vmap,
1506 struct vm_area_struct **src_vmap)
1507 {
1508 int err;
1509
1510 mmap_read_lock(mm);
1511 err = find_vmas_mm_locked(mm, dst_start, src_start, dst_vmap, src_vmap);
1512 if (err)
1513 mmap_read_unlock(mm);
1514 return err;
1515 }
1516
1517 static void uffd_move_unlock(struct vm_area_struct *dst_vma,
1518 struct vm_area_struct *src_vma)
1519 {
1520 mmap_assert_locked(src_vma->vm_mm);
1521 mmap_read_unlock(dst_vma->vm_mm);
1522 }
1523 #endif
1524
1525 /**
1526 * move_pages - move arbitrary anonymous pages of an existing vma
1527 * @ctx: pointer to the userfaultfd context
1528 * @dst_start: start of the destination virtual memory range
1529 * @src_start: start of the source virtual memory range
1530 * @len: length of the virtual memory range
1531 * @mode: flags from uffdio_move.mode
1532 *
1533 * It will either use the mmap_lock in read mode or per-vma locks
1534 *
1535 * move_pages() remaps arbitrary anonymous pages atomically in zero
1536 * copy. It only works on non shared anonymous pages because those can
1537 * be relocated without generating non linear anon_vmas in the rmap
1538 * code.
1539 *
1540 * It provides a zero copy mechanism to handle userspace page faults.
1541 * The source vma pages should have mapcount == 1, which can be
1542 * enforced by using madvise(MADV_DONTFORK) on src vma.
1543 *
1544 * The thread receiving the page during the userland page fault
1545 * will receive the faulting page in the source vma through the network,
1546 * storage or any other I/O device (MADV_DONTFORK in the source vma
1547 * avoids move_pages() to fail with -EBUSY if the process forks before
1548 * move_pages() is called), then it will call move_pages() to map the
1549 * page in the faulting address in the destination vma.
1550 *
1551 * This userfaultfd command works purely via pagetables, so it's the
1552 * most efficient way to move physical non shared anonymous pages
1553 * across different virtual addresses. Unlike mremap()/mmap()/munmap()
1554 * it does not create any new vmas. The mapping in the destination
1555 * address is atomic.
1556 *
1557 * It only works if the vma protection bits are identical from the
1558 * source and destination vma.
1559 *
1560 * It can remap non shared anonymous pages within the same vma too.
1561 *
1562 * If the source virtual memory range has any unmapped holes, or if
1563 * the destination virtual memory range is not a whole unmapped hole,
1564 * move_pages() will fail respectively with -ENOENT or -EEXIST. This
1565 * provides a very strict behavior to avoid any chance of memory
1566 * corruption going unnoticed if there are userland race conditions.
1567 * Only one thread should resolve the userland page fault at any given
1568 * time for any given faulting address. This means that if two threads
1569 * try to both call move_pages() on the same destination address at the
1570 * same time, the second thread will get an explicit error from this
1571 * command.
1572 *
1573 * The command retval will return "len" is successful. The command
1574 * however can be interrupted by fatal signals or errors. If
1575 * interrupted it will return the number of bytes successfully
1576 * remapped before the interruption if any, or the negative error if
1577 * none. It will never return zero. Either it will return an error or
1578 * an amount of bytes successfully moved. If the retval reports a
1579 * "short" remap, the move_pages() command should be repeated by
1580 * userland with src+retval, dst+reval, len-retval if it wants to know
1581 * about the error that interrupted it.
1582 *
1583 * The UFFDIO_MOVE_MODE_ALLOW_SRC_HOLES flag can be specified to
1584 * prevent -ENOENT errors to materialize if there are holes in the
1585 * source virtual range that is being remapped. The holes will be
1586 * accounted as successfully remapped in the retval of the
1587 * command. This is mostly useful to remap hugepage naturally aligned
1588 * virtual regions without knowing if there are transparent hugepage
1589 * in the regions or not, but preventing the risk of having to split
1590 * the hugepmd during the remap.
1591 *
1592 * If there's any rmap walk that is taking the anon_vma locks without
1593 * first obtaining the folio lock (the only current instance is
1594 * folio_referenced), they will have to verify if the folio->mapping
1595 * has changed after taking the anon_vma lock. If it changed they
1596 * should release the lock and retry obtaining a new anon_vma, because
1597 * it means the anon_vma was changed by move_pages() before the lock
1598 * could be obtained. This is the only additional complexity added to
1599 * the rmap code to provide this anonymous page remapping functionality.
1600 */
1601 ssize_t move_pages(struct userfaultfd_ctx *ctx, unsigned long dst_start,
1602 unsigned long src_start, unsigned long len, __u64 mode)
1603 {
1604 struct mm_struct *mm = ctx->mm;
1605 struct vm_area_struct *src_vma, *dst_vma;
1606 unsigned long src_addr, dst_addr;
1607 pmd_t *src_pmd, *dst_pmd;
1608 long err = -EINVAL;
1609 ssize_t moved = 0;
1610
1611 /* Sanitize the command parameters. */
1612 if (WARN_ON_ONCE(src_start & ~PAGE_MASK) ||
1613 WARN_ON_ONCE(dst_start & ~PAGE_MASK) ||
1614 WARN_ON_ONCE(len & ~PAGE_MASK))
1615 goto out;
1616
1617 /* Does the address range wrap, or is the span zero-sized? */
1618 if (WARN_ON_ONCE(src_start + len <= src_start) ||
1619 WARN_ON_ONCE(dst_start + len <= dst_start))
1620 goto out;
1621
1622 err = uffd_move_lock(mm, dst_start, src_start, &dst_vma, &src_vma);
1623 if (err)
1624 goto out;
1625
1626 /* Re-check after taking map_changing_lock */
1627 err = -EAGAIN;
1628 down_read(&ctx->map_changing_lock);
1629 if (likely(atomic_read(&ctx->mmap_changing)))
1630 goto out_unlock;
1631 /*
1632 * Make sure the vma is not shared, that the src and dst remap
1633 * ranges are both valid and fully within a single existing
1634 * vma.
1635 */
1636 err = -EINVAL;
1637 if (src_vma->vm_flags & VM_SHARED)
1638 goto out_unlock;
1639 if (src_start + len > src_vma->vm_end)
1640 goto out_unlock;
1641
1642 if (dst_vma->vm_flags & VM_SHARED)
1643 goto out_unlock;
1644 if (dst_start + len > dst_vma->vm_end)
1645 goto out_unlock;
1646
1647 err = validate_move_areas(ctx, src_vma, dst_vma);
1648 if (err)
1649 goto out_unlock;
1650
1651 for (src_addr = src_start, dst_addr = dst_start;
1652 src_addr < src_start + len;) {
1653 spinlock_t *ptl;
1654 pmd_t dst_pmdval;
1655 unsigned long step_size;
1656
1657 /*
1658 * Below works because anonymous area would not have a
1659 * transparent huge PUD. If file-backed support is added,
1660 * that case would need to be handled here.
1661 */
1662 src_pmd = mm_find_pmd(mm, src_addr);
1663 if (unlikely(!src_pmd)) {
1664 if (!(mode & UFFDIO_MOVE_MODE_ALLOW_SRC_HOLES)) {
1665 err = -ENOENT;
1666 break;
1667 }
1668 src_pmd = mm_alloc_pmd(mm, src_addr);
1669 if (unlikely(!src_pmd)) {
1670 err = -ENOMEM;
1671 break;
1672 }
1673 }
1674 dst_pmd = mm_alloc_pmd(mm, dst_addr);
1675 if (unlikely(!dst_pmd)) {
1676 err = -ENOMEM;
1677 break;
1678 }
1679
1680 dst_pmdval = pmdp_get_lockless(dst_pmd);
1681 /*
1682 * If the dst_pmd is mapped as THP don't override it and just
1683 * be strict. If dst_pmd changes into TPH after this check, the
1684 * move_pages_huge_pmd() will detect the change and retry
1685 * while move_pages_pte() will detect the change and fail.
1686 */
1687 if (unlikely(pmd_trans_huge(dst_pmdval))) {
1688 err = -EEXIST;
1689 break;
1690 }
1691
1692 ptl = pmd_trans_huge_lock(src_pmd, src_vma);
1693 if (ptl) {
1694 if (pmd_devmap(*src_pmd)) {
1695 spin_unlock(ptl);
1696 err = -ENOENT;
1697 break;
1698 }
1699
1700 /* Check if we can move the pmd without splitting it. */
1701 if (move_splits_huge_pmd(dst_addr, src_addr, src_start + len) ||
1702 !pmd_none(dst_pmdval)) {
1703 struct folio *folio = pmd_folio(*src_pmd);
1704
1705 if (!folio || (!is_huge_zero_folio(folio) &&
1706 !PageAnonExclusive(&folio->page))) {
1707 spin_unlock(ptl);
1708 err = -EBUSY;
1709 break;
1710 }
1711
1712 spin_unlock(ptl);
1713 split_huge_pmd(src_vma, src_pmd, src_addr);
1714 /* The folio will be split by move_pages_pte() */
1715 continue;
1716 }
1717
1718 err = move_pages_huge_pmd(mm, dst_pmd, src_pmd,
1719 dst_pmdval, dst_vma, src_vma,
1720 dst_addr, src_addr);
1721 step_size = HPAGE_PMD_SIZE;
1722 } else {
1723 if (pmd_none(*src_pmd)) {
1724 if (!(mode & UFFDIO_MOVE_MODE_ALLOW_SRC_HOLES)) {
1725 err = -ENOENT;
1726 break;
1727 }
1728 if (unlikely(__pte_alloc(mm, src_pmd))) {
1729 err = -ENOMEM;
1730 break;
1731 }
1732 }
1733
1734 if (unlikely(pte_alloc(mm, dst_pmd))) {
1735 err = -ENOMEM;
1736 break;
1737 }
1738
1739 err = move_pages_pte(mm, dst_pmd, src_pmd,
1740 dst_vma, src_vma,
1741 dst_addr, src_addr, mode);
1742 step_size = PAGE_SIZE;
1743 }
1744
1745 cond_resched();
1746
1747 if (fatal_signal_pending(current)) {
1748 /* Do not override an error */
1749 if (!err || err == -EAGAIN)
1750 err = -EINTR;
1751 break;
1752 }
1753
1754 if (err) {
1755 if (err == -EAGAIN)
1756 continue;
1757 break;
1758 }
1759
1760 /* Proceed to the next page */
1761 dst_addr += step_size;
1762 src_addr += step_size;
1763 moved += step_size;
1764 }
1765
1766 out_unlock:
1767 up_read(&ctx->map_changing_lock);
1768 uffd_move_unlock(dst_vma, src_vma);
1769 out:
1770 VM_WARN_ON(moved < 0);
1771 VM_WARN_ON(err > 0);
1772 VM_WARN_ON(!moved && !err);
1773 return moved ? moved : err;
1774 }
1775
1776 static void userfaultfd_set_vm_flags(struct vm_area_struct *vma,
1777 vm_flags_t flags)
1778 {
1779 const bool uffd_wp_changed = (vma->vm_flags ^ flags) & VM_UFFD_WP;
1780
1781 vm_flags_reset(vma, flags);
1782 /*
1783 * For shared mappings, we want to enable writenotify while
1784 * userfaultfd-wp is enabled (see vma_wants_writenotify()). We'll simply
1785 * recalculate vma->vm_page_prot whenever userfaultfd-wp changes.
1786 */
1787 if ((vma->vm_flags & VM_SHARED) && uffd_wp_changed)
1788 vma_set_page_prot(vma);
1789 }
1790
1791 static void userfaultfd_set_ctx(struct vm_area_struct *vma,
1792 struct userfaultfd_ctx *ctx,
1793 unsigned long flags)
1794 {
1795 vma_start_write(vma);
1796 vma->vm_userfaultfd_ctx = (struct vm_userfaultfd_ctx){ctx};
1797 userfaultfd_set_vm_flags(vma,
1798 (vma->vm_flags & ~__VM_UFFD_FLAGS) | flags);
1799 }
1800
1801 void userfaultfd_reset_ctx(struct vm_area_struct *vma)
1802 {
1803 userfaultfd_set_ctx(vma, NULL, 0);
1804 }
1805
1806 struct vm_area_struct *userfaultfd_clear_vma(struct vma_iterator *vmi,
1807 struct vm_area_struct *prev,
1808 struct vm_area_struct *vma,
1809 unsigned long start,
1810 unsigned long end)
1811 {
1812 struct vm_area_struct *ret;
1813
1814 /* Reset ptes for the whole vma range if wr-protected */
1815 if (userfaultfd_wp(vma))
1816 uffd_wp_range(vma, start, end - start, false);
1817
1818 ret = vma_modify_flags_uffd(vmi, prev, vma, start, end,
1819 vma->vm_flags & ~__VM_UFFD_FLAGS,
1820 NULL_VM_UFFD_CTX);
1821
1822 /*
1823 * In the vma_merge() successful mprotect-like case 8:
1824 * the next vma was merged into the current one and
1825 * the current one has not been updated yet.
1826 */
1827 if (!IS_ERR(ret))
1828 userfaultfd_reset_ctx(ret);
1829
1830 return ret;
1831 }
1832
1833 /* Assumes mmap write lock taken, and mm_struct pinned. */
1834 int userfaultfd_register_range(struct userfaultfd_ctx *ctx,
1835 struct vm_area_struct *vma,
1836 unsigned long vm_flags,
1837 unsigned long start, unsigned long end,
1838 bool wp_async)
1839 {
1840 VMA_ITERATOR(vmi, ctx->mm, start);
1841 struct vm_area_struct *prev = vma_prev(&vmi);
1842 unsigned long vma_end;
1843 unsigned long new_flags;
1844
1845 if (vma->vm_start < start)
1846 prev = vma;
1847
1848 for_each_vma_range(vmi, vma, end) {
1849 cond_resched();
1850
1851 BUG_ON(!vma_can_userfault(vma, vm_flags, wp_async));
1852 BUG_ON(vma->vm_userfaultfd_ctx.ctx &&
1853 vma->vm_userfaultfd_ctx.ctx != ctx);
1854 WARN_ON(!(vma->vm_flags & VM_MAYWRITE));
1855
1856 /*
1857 * Nothing to do: this vma is already registered into this
1858 * userfaultfd and with the right tracking mode too.
1859 */
1860 if (vma->vm_userfaultfd_ctx.ctx == ctx &&
1861 (vma->vm_flags & vm_flags) == vm_flags)
1862 goto skip;
1863
1864 if (vma->vm_start > start)
1865 start = vma->vm_start;
1866 vma_end = min(end, vma->vm_end);
1867
1868 new_flags = (vma->vm_flags & ~__VM_UFFD_FLAGS) | vm_flags;
1869 vma = vma_modify_flags_uffd(&vmi, prev, vma, start, vma_end,
1870 new_flags,
1871 (struct vm_userfaultfd_ctx){ctx});
1872 if (IS_ERR(vma))
1873 return PTR_ERR(vma);
1874
1875 /*
1876 * In the vma_merge() successful mprotect-like case 8:
1877 * the next vma was merged into the current one and
1878 * the current one has not been updated yet.
1879 */
1880 userfaultfd_set_ctx(vma, ctx, vm_flags);
1881
1882 if (is_vm_hugetlb_page(vma) && uffd_disable_huge_pmd_share(vma))
1883 hugetlb_unshare_all_pmds(vma);
1884
1885 skip:
1886 prev = vma;
1887 start = vma->vm_end;
1888 }
1889
1890 return 0;
1891 }
1892
1893 void userfaultfd_release_new(struct userfaultfd_ctx *ctx)
1894 {
1895 struct mm_struct *mm = ctx->mm;
1896 struct vm_area_struct *vma;
1897 VMA_ITERATOR(vmi, mm, 0);
1898
1899 /* the various vma->vm_userfaultfd_ctx still points to it */
1900 mmap_write_lock(mm);
1901 for_each_vma(vmi, vma) {
1902 if (vma->vm_userfaultfd_ctx.ctx == ctx)
1903 userfaultfd_reset_ctx(vma);
1904 }
1905 mmap_write_unlock(mm);
1906 }
1907
1908 void userfaultfd_release_all(struct mm_struct *mm,
1909 struct userfaultfd_ctx *ctx)
1910 {
1911 struct vm_area_struct *vma, *prev;
1912 VMA_ITERATOR(vmi, mm, 0);
1913
1914 if (!mmget_not_zero(mm))
1915 return;
1916
1917 /*
1918 * Flush page faults out of all CPUs. NOTE: all page faults
1919 * must be retried without returning VM_FAULT_SIGBUS if
1920 * userfaultfd_ctx_get() succeeds but vma->vma_userfault_ctx
1921 * changes while handle_userfault released the mmap_lock. So
1922 * it's critical that released is set to true (above), before
1923 * taking the mmap_lock for writing.
1924 */
1925 mmap_write_lock(mm);
1926 prev = NULL;
1927 for_each_vma(vmi, vma) {
1928 cond_resched();
1929 BUG_ON(!!vma->vm_userfaultfd_ctx.ctx ^
1930 !!(vma->vm_flags & __VM_UFFD_FLAGS));
1931 if (vma->vm_userfaultfd_ctx.ctx != ctx) {
1932 prev = vma;
1933 continue;
1934 }
1935
1936 vma = userfaultfd_clear_vma(&vmi, prev, vma,
1937 vma->vm_start, vma->vm_end);
1938 prev = vma;
1939 }
1940 mmap_write_unlock(mm);
1941 mmput(mm);
1942 }
Kernel DRM miscellaneous fixes and cross-tree changes