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
find_dst_vma(struct mm_struct * dst_mm,unsigned long dst_start,unsigned long len)23 struct vm_area_struct *find_dst_vma(struct mm_struct *dst_mm,
24 unsigned long dst_start,
25 unsigned long len)
26 {
27 /*
28 * Make sure that the dst range is both valid and fully within a
29 * single existing vma.
30 */
31 struct vm_area_struct *dst_vma;
32
33 dst_vma = find_vma(dst_mm, dst_start);
34 if (!dst_vma)
35 return NULL;
36
37 if (dst_start < dst_vma->vm_start ||
38 dst_start + len > dst_vma->vm_end)
39 return NULL;
40
41 /*
42 * Check the vma is registered in uffd, this is required to
43 * enforce the VM_MAYWRITE check done at uffd registration
44 * time.
45 */
46 if (!dst_vma->vm_userfaultfd_ctx.ctx)
47 return NULL;
48
49 return dst_vma;
50 }
51
52 /*
53 * Install PTEs, to map dst_addr (within dst_vma) to page.
54 *
55 * This function handles both MCOPY_ATOMIC_NORMAL and _CONTINUE for both shmem
56 * and anon, and for both shared and private VMAs.
57 */
mfill_atomic_install_pte(struct mm_struct * dst_mm,pmd_t * dst_pmd,struct vm_area_struct * dst_vma,unsigned long dst_addr,struct page * page,bool newly_allocated,bool wp_copy)58 int mfill_atomic_install_pte(struct mm_struct *dst_mm, pmd_t *dst_pmd,
59 struct vm_area_struct *dst_vma,
60 unsigned long dst_addr, struct page *page,
61 bool newly_allocated, bool wp_copy)
62 {
63 int ret;
64 pte_t _dst_pte, *dst_pte;
65 bool writable = dst_vma->vm_flags & VM_WRITE;
66 bool vm_shared = dst_vma->vm_flags & VM_SHARED;
67 bool page_in_cache = page_mapping(page);
68 spinlock_t *ptl;
69 struct inode *inode;
70 pgoff_t offset, max_off;
71
72 _dst_pte = mk_pte(page, dst_vma->vm_page_prot);
73 _dst_pte = pte_mkdirty(_dst_pte);
74 if (page_in_cache && !vm_shared)
75 writable = false;
76
77 /*
78 * Always mark a PTE as write-protected when needed, regardless of
79 * VM_WRITE, which the user might change.
80 */
81 if (wp_copy) {
82 _dst_pte = pte_mkuffd_wp(_dst_pte);
83 writable = false;
84 }
85
86 if (writable)
87 _dst_pte = pte_mkwrite(_dst_pte);
88 else
89 /*
90 * We need this to make sure write bit removed; as mk_pte()
91 * could return a pte with write bit set.
92 */
93 _dst_pte = pte_wrprotect(_dst_pte);
94
95 dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl);
96
97 if (vma_is_shmem(dst_vma)) {
98 /* serialize against truncate with the page table lock */
99 inode = dst_vma->vm_file->f_inode;
100 offset = linear_page_index(dst_vma, dst_addr);
101 max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
102 ret = -EFAULT;
103 if (unlikely(offset >= max_off))
104 goto out_unlock;
105 }
106
107 ret = -EEXIST;
108 /*
109 * We allow to overwrite a pte marker: consider when both MISSING|WP
110 * registered, we firstly wr-protect a none pte which has no page cache
111 * page backing it, then access the page.
112 */
113 if (!pte_none_mostly(*dst_pte))
114 goto out_unlock;
115
116 if (page_in_cache) {
117 /* Usually, cache pages are already added to LRU */
118 if (newly_allocated)
119 lru_cache_add(page);
120 page_add_file_rmap(page, dst_vma, false);
121 } else {
122 page_add_new_anon_rmap(page, dst_vma, dst_addr);
123 lru_cache_add_inactive_or_unevictable(page, dst_vma);
124 }
125
126 /*
127 * Must happen after rmap, as mm_counter() checks mapping (via
128 * PageAnon()), which is set by __page_set_anon_rmap().
129 */
130 inc_mm_counter(dst_mm, mm_counter(page));
131
132 set_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte);
133
134 /* No need to invalidate - it was non-present before */
135 update_mmu_cache(dst_vma, dst_addr, dst_pte);
136 ret = 0;
137 out_unlock:
138 pte_unmap_unlock(dst_pte, ptl);
139 return ret;
140 }
141
mcopy_atomic_pte(struct mm_struct * dst_mm,pmd_t * dst_pmd,struct vm_area_struct * dst_vma,unsigned long dst_addr,unsigned long src_addr,struct page ** pagep,bool wp_copy)142 static int mcopy_atomic_pte(struct mm_struct *dst_mm,
143 pmd_t *dst_pmd,
144 struct vm_area_struct *dst_vma,
145 unsigned long dst_addr,
146 unsigned long src_addr,
147 struct page **pagep,
148 bool wp_copy)
149 {
150 void *page_kaddr;
151 int ret;
152 struct page *page;
153
154 if (!*pagep) {
155 ret = -ENOMEM;
156 page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, dst_vma, dst_addr);
157 if (!page)
158 goto out;
159
160 page_kaddr = kmap_local_page(page);
161 /*
162 * The read mmap_lock is held here. Despite the
163 * mmap_lock being read recursive a deadlock is still
164 * possible if a writer has taken a lock. For example:
165 *
166 * process A thread 1 takes read lock on own mmap_lock
167 * process A thread 2 calls mmap, blocks taking write lock
168 * process B thread 1 takes page fault, read lock on own mmap lock
169 * process B thread 2 calls mmap, blocks taking write lock
170 * process A thread 1 blocks taking read lock on process B
171 * process B thread 1 blocks taking read lock on process A
172 *
173 * Disable page faults to prevent potential deadlock
174 * and retry the copy outside the mmap_lock.
175 */
176 pagefault_disable();
177 ret = copy_from_user(page_kaddr,
178 (const void __user *) src_addr,
179 PAGE_SIZE);
180 pagefault_enable();
181 kunmap_local(page_kaddr);
182
183 /* fallback to copy_from_user outside mmap_lock */
184 if (unlikely(ret)) {
185 ret = -ENOENT;
186 *pagep = page;
187 /* don't free the page */
188 goto out;
189 }
190
191 flush_dcache_page(page);
192 } else {
193 page = *pagep;
194 *pagep = NULL;
195 }
196
197 /*
198 * The memory barrier inside __SetPageUptodate makes sure that
199 * preceding stores to the page contents become visible before
200 * the set_pte_at() write.
201 */
202 __SetPageUptodate(page);
203
204 ret = -ENOMEM;
205 if (mem_cgroup_charge(page_folio(page), dst_mm, GFP_KERNEL))
206 goto out_release;
207
208 ret = mfill_atomic_install_pte(dst_mm, dst_pmd, dst_vma, dst_addr,
209 page, true, wp_copy);
210 if (ret)
211 goto out_release;
212 out:
213 return ret;
214 out_release:
215 put_page(page);
216 goto out;
217 }
218
mfill_zeropage_pte(struct mm_struct * dst_mm,pmd_t * dst_pmd,struct vm_area_struct * dst_vma,unsigned long dst_addr)219 static int mfill_zeropage_pte(struct mm_struct *dst_mm,
220 pmd_t *dst_pmd,
221 struct vm_area_struct *dst_vma,
222 unsigned long dst_addr)
223 {
224 pte_t _dst_pte, *dst_pte;
225 spinlock_t *ptl;
226 int ret;
227 pgoff_t offset, max_off;
228 struct inode *inode;
229
230 _dst_pte = pte_mkspecial(pfn_pte(my_zero_pfn(dst_addr),
231 dst_vma->vm_page_prot));
232 dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl);
233 if (dst_vma->vm_file) {
234 /* the shmem MAP_PRIVATE case requires checking the i_size */
235 inode = dst_vma->vm_file->f_inode;
236 offset = linear_page_index(dst_vma, dst_addr);
237 max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
238 ret = -EFAULT;
239 if (unlikely(offset >= max_off))
240 goto out_unlock;
241 }
242 ret = -EEXIST;
243 if (!pte_none(*dst_pte))
244 goto out_unlock;
245 set_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte);
246 /* No need to invalidate - it was non-present before */
247 update_mmu_cache(dst_vma, dst_addr, dst_pte);
248 ret = 0;
249 out_unlock:
250 pte_unmap_unlock(dst_pte, ptl);
251 return ret;
252 }
253
254 /* Handles UFFDIO_CONTINUE for all shmem VMAs (shared or private). */
mcontinue_atomic_pte(struct mm_struct * dst_mm,pmd_t * dst_pmd,struct vm_area_struct * dst_vma,unsigned long dst_addr,bool wp_copy)255 static int mcontinue_atomic_pte(struct mm_struct *dst_mm,
256 pmd_t *dst_pmd,
257 struct vm_area_struct *dst_vma,
258 unsigned long dst_addr,
259 bool wp_copy)
260 {
261 struct inode *inode = file_inode(dst_vma->vm_file);
262 pgoff_t pgoff = linear_page_index(dst_vma, dst_addr);
263 struct folio *folio;
264 struct page *page;
265 int ret;
266
267 ret = shmem_get_folio(inode, pgoff, &folio, SGP_NOALLOC);
268 /* Our caller expects us to return -EFAULT if we failed to find folio */
269 if (ret == -ENOENT)
270 ret = -EFAULT;
271 if (ret)
272 goto out;
273 if (!folio) {
274 ret = -EFAULT;
275 goto out;
276 }
277
278 page = folio_file_page(folio, pgoff);
279 if (PageHWPoison(page)) {
280 ret = -EIO;
281 goto out_release;
282 }
283
284 ret = mfill_atomic_install_pte(dst_mm, dst_pmd, dst_vma, dst_addr,
285 page, false, wp_copy);
286 if (ret)
287 goto out_release;
288
289 folio_unlock(folio);
290 ret = 0;
291 out:
292 return ret;
293 out_release:
294 folio_unlock(folio);
295 folio_put(folio);
296 goto out;
297 }
298
mm_alloc_pmd(struct mm_struct * mm,unsigned long address)299 static pmd_t *mm_alloc_pmd(struct mm_struct *mm, unsigned long address)
300 {
301 pgd_t *pgd;
302 p4d_t *p4d;
303 pud_t *pud;
304
305 pgd = pgd_offset(mm, address);
306 p4d = p4d_alloc(mm, pgd, address);
307 if (!p4d)
308 return NULL;
309 pud = pud_alloc(mm, p4d, address);
310 if (!pud)
311 return NULL;
312 /*
313 * Note that we didn't run this because the pmd was
314 * missing, the *pmd may be already established and in
315 * turn it may also be a trans_huge_pmd.
316 */
317 return pmd_alloc(mm, pud, address);
318 }
319
320 #ifdef CONFIG_HUGETLB_PAGE
321 /*
322 * __mcopy_atomic processing for HUGETLB vmas. Note that this routine is
323 * called with mmap_lock held, it will release mmap_lock before returning.
324 */
__mcopy_atomic_hugetlb(struct mm_struct * dst_mm,struct vm_area_struct * dst_vma,unsigned long dst_start,unsigned long src_start,unsigned long len,enum mcopy_atomic_mode mode,bool wp_copy)325 static __always_inline ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm,
326 struct vm_area_struct *dst_vma,
327 unsigned long dst_start,
328 unsigned long src_start,
329 unsigned long len,
330 enum mcopy_atomic_mode mode,
331 bool wp_copy)
332 {
333 int vm_shared = dst_vma->vm_flags & VM_SHARED;
334 ssize_t err;
335 pte_t *dst_pte;
336 unsigned long src_addr, dst_addr;
337 long copied;
338 struct page *page;
339 unsigned long vma_hpagesize;
340 pgoff_t idx;
341 u32 hash;
342 struct address_space *mapping;
343
344 /*
345 * There is no default zero huge page for all huge page sizes as
346 * supported by hugetlb. A PMD_SIZE huge pages may exist as used
347 * by THP. Since we can not reliably insert a zero page, this
348 * feature is not supported.
349 */
350 if (mode == MCOPY_ATOMIC_ZEROPAGE) {
351 mmap_read_unlock(dst_mm);
352 return -EINVAL;
353 }
354
355 src_addr = src_start;
356 dst_addr = dst_start;
357 copied = 0;
358 page = NULL;
359 vma_hpagesize = vma_kernel_pagesize(dst_vma);
360
361 /*
362 * Validate alignment based on huge page size
363 */
364 err = -EINVAL;
365 if (dst_start & (vma_hpagesize - 1) || len & (vma_hpagesize - 1))
366 goto out_unlock;
367
368 retry:
369 /*
370 * On routine entry dst_vma is set. If we had to drop mmap_lock and
371 * retry, dst_vma will be set to NULL and we must lookup again.
372 */
373 if (!dst_vma) {
374 err = -ENOENT;
375 dst_vma = find_dst_vma(dst_mm, dst_start, len);
376 if (!dst_vma || !is_vm_hugetlb_page(dst_vma))
377 goto out_unlock;
378
379 err = -EINVAL;
380 if (vma_hpagesize != vma_kernel_pagesize(dst_vma))
381 goto out_unlock;
382
383 vm_shared = dst_vma->vm_flags & VM_SHARED;
384 }
385
386 /*
387 * If not shared, ensure the dst_vma has a anon_vma.
388 */
389 err = -ENOMEM;
390 if (!vm_shared) {
391 if (unlikely(anon_vma_prepare(dst_vma)))
392 goto out_unlock;
393 }
394
395 while (src_addr < src_start + len) {
396 BUG_ON(dst_addr >= dst_start + len);
397
398 /*
399 * Serialize via vma_lock and hugetlb_fault_mutex.
400 * vma_lock ensures the dst_pte remains valid even
401 * in the case of shared pmds. fault mutex prevents
402 * races with other faulting threads.
403 */
404 idx = linear_page_index(dst_vma, dst_addr);
405 mapping = dst_vma->vm_file->f_mapping;
406 hash = hugetlb_fault_mutex_hash(mapping, idx);
407 mutex_lock(&hugetlb_fault_mutex_table[hash]);
408 hugetlb_vma_lock_read(dst_vma);
409
410 err = -ENOMEM;
411 dst_pte = huge_pte_alloc(dst_mm, dst_vma, dst_addr, vma_hpagesize);
412 if (!dst_pte) {
413 hugetlb_vma_unlock_read(dst_vma);
414 mutex_unlock(&hugetlb_fault_mutex_table[hash]);
415 goto out_unlock;
416 }
417
418 if (mode != MCOPY_ATOMIC_CONTINUE &&
419 !huge_pte_none_mostly(huge_ptep_get(dst_pte))) {
420 err = -EEXIST;
421 hugetlb_vma_unlock_read(dst_vma);
422 mutex_unlock(&hugetlb_fault_mutex_table[hash]);
423 goto out_unlock;
424 }
425
426 err = hugetlb_mcopy_atomic_pte(dst_mm, dst_pte, dst_vma,
427 dst_addr, src_addr, mode, &page,
428 wp_copy);
429
430 hugetlb_vma_unlock_read(dst_vma);
431 mutex_unlock(&hugetlb_fault_mutex_table[hash]);
432
433 cond_resched();
434
435 if (unlikely(err == -ENOENT)) {
436 mmap_read_unlock(dst_mm);
437 BUG_ON(!page);
438
439 err = copy_huge_page_from_user(page,
440 (const void __user *)src_addr,
441 vma_hpagesize / PAGE_SIZE,
442 true);
443 if (unlikely(err)) {
444 err = -EFAULT;
445 goto out;
446 }
447 mmap_read_lock(dst_mm);
448
449 dst_vma = NULL;
450 goto retry;
451 } else
452 BUG_ON(page);
453
454 if (!err) {
455 dst_addr += vma_hpagesize;
456 src_addr += vma_hpagesize;
457 copied += vma_hpagesize;
458
459 if (fatal_signal_pending(current))
460 err = -EINTR;
461 }
462 if (err)
463 break;
464 }
465
466 out_unlock:
467 mmap_read_unlock(dst_mm);
468 out:
469 if (page)
470 put_page(page);
471 BUG_ON(copied < 0);
472 BUG_ON(err > 0);
473 BUG_ON(!copied && !err);
474 return copied ? copied : err;
475 }
476 #else /* !CONFIG_HUGETLB_PAGE */
477 /* fail at build time if gcc attempts to use this */
478 extern ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm,
479 struct vm_area_struct *dst_vma,
480 unsigned long dst_start,
481 unsigned long src_start,
482 unsigned long len,
483 enum mcopy_atomic_mode mode,
484 bool wp_copy);
485 #endif /* CONFIG_HUGETLB_PAGE */
486
mfill_atomic_pte(struct mm_struct * dst_mm,pmd_t * dst_pmd,struct vm_area_struct * dst_vma,unsigned long dst_addr,unsigned long src_addr,struct page ** page,enum mcopy_atomic_mode mode,bool wp_copy)487 static __always_inline ssize_t mfill_atomic_pte(struct mm_struct *dst_mm,
488 pmd_t *dst_pmd,
489 struct vm_area_struct *dst_vma,
490 unsigned long dst_addr,
491 unsigned long src_addr,
492 struct page **page,
493 enum mcopy_atomic_mode mode,
494 bool wp_copy)
495 {
496 ssize_t err;
497
498 if (mode == MCOPY_ATOMIC_CONTINUE) {
499 return mcontinue_atomic_pte(dst_mm, dst_pmd, dst_vma, dst_addr,
500 wp_copy);
501 }
502
503 /*
504 * The normal page fault path for a shmem will invoke the
505 * fault, fill the hole in the file and COW it right away. The
506 * result generates plain anonymous memory. So when we are
507 * asked to fill an hole in a MAP_PRIVATE shmem mapping, we'll
508 * generate anonymous memory directly without actually filling
509 * the hole. For the MAP_PRIVATE case the robustness check
510 * only happens in the pagetable (to verify it's still none)
511 * and not in the radix tree.
512 */
513 if (!(dst_vma->vm_flags & VM_SHARED)) {
514 if (mode == MCOPY_ATOMIC_NORMAL)
515 err = mcopy_atomic_pte(dst_mm, dst_pmd, dst_vma,
516 dst_addr, src_addr, page,
517 wp_copy);
518 else
519 err = mfill_zeropage_pte(dst_mm, dst_pmd,
520 dst_vma, dst_addr);
521 } else {
522 err = shmem_mfill_atomic_pte(dst_mm, dst_pmd, dst_vma,
523 dst_addr, src_addr,
524 mode != MCOPY_ATOMIC_NORMAL,
525 wp_copy, page);
526 }
527
528 return err;
529 }
530
__mcopy_atomic(struct mm_struct * dst_mm,unsigned long dst_start,unsigned long src_start,unsigned long len,enum mcopy_atomic_mode mcopy_mode,atomic_t * mmap_changing,__u64 mode)531 static __always_inline ssize_t __mcopy_atomic(struct mm_struct *dst_mm,
532 unsigned long dst_start,
533 unsigned long src_start,
534 unsigned long len,
535 enum mcopy_atomic_mode mcopy_mode,
536 atomic_t *mmap_changing,
537 __u64 mode)
538 {
539 struct vm_area_struct *dst_vma;
540 ssize_t err;
541 pmd_t *dst_pmd;
542 unsigned long src_addr, dst_addr;
543 long copied;
544 struct page *page;
545 bool wp_copy;
546
547 /*
548 * Sanitize the command parameters:
549 */
550 BUG_ON(dst_start & ~PAGE_MASK);
551 BUG_ON(len & ~PAGE_MASK);
552
553 /* Does the address range wrap, or is the span zero-sized? */
554 BUG_ON(src_start + len <= src_start);
555 BUG_ON(dst_start + len <= dst_start);
556
557 src_addr = src_start;
558 dst_addr = dst_start;
559 copied = 0;
560 page = NULL;
561 retry:
562 mmap_read_lock(dst_mm);
563
564 /*
565 * If memory mappings are changing because of non-cooperative
566 * operation (e.g. mremap) running in parallel, bail out and
567 * request the user to retry later
568 */
569 err = -EAGAIN;
570 if (mmap_changing && atomic_read(mmap_changing))
571 goto out_unlock;
572
573 /*
574 * Make sure the vma is not shared, that the dst range is
575 * both valid and fully within a single existing vma.
576 */
577 err = -ENOENT;
578 dst_vma = find_dst_vma(dst_mm, dst_start, len);
579 if (!dst_vma)
580 goto out_unlock;
581
582 err = -EINVAL;
583 /*
584 * shmem_zero_setup is invoked in mmap for MAP_ANONYMOUS|MAP_SHARED but
585 * it will overwrite vm_ops, so vma_is_anonymous must return false.
586 */
587 if (WARN_ON_ONCE(vma_is_anonymous(dst_vma) &&
588 dst_vma->vm_flags & VM_SHARED))
589 goto out_unlock;
590
591 /*
592 * validate 'mode' now that we know the dst_vma: don't allow
593 * a wrprotect copy if the userfaultfd didn't register as WP.
594 */
595 wp_copy = mode & UFFDIO_COPY_MODE_WP;
596 if (wp_copy && !(dst_vma->vm_flags & VM_UFFD_WP))
597 goto out_unlock;
598
599 /*
600 * If this is a HUGETLB vma, pass off to appropriate routine
601 */
602 if (is_vm_hugetlb_page(dst_vma))
603 return __mcopy_atomic_hugetlb(dst_mm, dst_vma, dst_start,
604 src_start, len, mcopy_mode,
605 wp_copy);
606
607 if (!vma_is_anonymous(dst_vma) && !vma_is_shmem(dst_vma))
608 goto out_unlock;
609 if (!vma_is_shmem(dst_vma) && mcopy_mode == MCOPY_ATOMIC_CONTINUE)
610 goto out_unlock;
611
612 /*
613 * Ensure the dst_vma has a anon_vma or this page
614 * would get a NULL anon_vma when moved in the
615 * dst_vma.
616 */
617 err = -ENOMEM;
618 if (!(dst_vma->vm_flags & VM_SHARED) &&
619 unlikely(anon_vma_prepare(dst_vma)))
620 goto out_unlock;
621
622 while (src_addr < src_start + len) {
623 pmd_t dst_pmdval;
624
625 BUG_ON(dst_addr >= dst_start + len);
626
627 dst_pmd = mm_alloc_pmd(dst_mm, dst_addr);
628 if (unlikely(!dst_pmd)) {
629 err = -ENOMEM;
630 break;
631 }
632
633 dst_pmdval = pmd_read_atomic(dst_pmd);
634 /*
635 * If the dst_pmd is mapped as THP don't
636 * override it and just be strict.
637 */
638 if (unlikely(pmd_trans_huge(dst_pmdval))) {
639 err = -EEXIST;
640 break;
641 }
642 if (unlikely(pmd_none(dst_pmdval)) &&
643 unlikely(__pte_alloc(dst_mm, dst_pmd))) {
644 err = -ENOMEM;
645 break;
646 }
647 /* If an huge pmd materialized from under us fail */
648 if (unlikely(pmd_trans_huge(*dst_pmd))) {
649 err = -EFAULT;
650 break;
651 }
652
653 BUG_ON(pmd_none(*dst_pmd));
654 BUG_ON(pmd_trans_huge(*dst_pmd));
655
656 err = mfill_atomic_pte(dst_mm, dst_pmd, dst_vma, dst_addr,
657 src_addr, &page, mcopy_mode, wp_copy);
658 cond_resched();
659
660 if (unlikely(err == -ENOENT)) {
661 void *page_kaddr;
662
663 mmap_read_unlock(dst_mm);
664 BUG_ON(!page);
665
666 page_kaddr = kmap_local_page(page);
667 err = copy_from_user(page_kaddr,
668 (const void __user *) src_addr,
669 PAGE_SIZE);
670 kunmap_local(page_kaddr);
671 if (unlikely(err)) {
672 err = -EFAULT;
673 goto out;
674 }
675 flush_dcache_page(page);
676 goto retry;
677 } else
678 BUG_ON(page);
679
680 if (!err) {
681 dst_addr += PAGE_SIZE;
682 src_addr += PAGE_SIZE;
683 copied += PAGE_SIZE;
684
685 if (fatal_signal_pending(current))
686 err = -EINTR;
687 }
688 if (err)
689 break;
690 }
691
692 out_unlock:
693 mmap_read_unlock(dst_mm);
694 out:
695 if (page)
696 put_page(page);
697 BUG_ON(copied < 0);
698 BUG_ON(err > 0);
699 BUG_ON(!copied && !err);
700 return copied ? copied : err;
701 }
702
mcopy_atomic(struct mm_struct * dst_mm,unsigned long dst_start,unsigned long src_start,unsigned long len,atomic_t * mmap_changing,__u64 mode)703 ssize_t mcopy_atomic(struct mm_struct *dst_mm, unsigned long dst_start,
704 unsigned long src_start, unsigned long len,
705 atomic_t *mmap_changing, __u64 mode)
706 {
707 return __mcopy_atomic(dst_mm, dst_start, src_start, len,
708 MCOPY_ATOMIC_NORMAL, mmap_changing, mode);
709 }
710
mfill_zeropage(struct mm_struct * dst_mm,unsigned long start,unsigned long len,atomic_t * mmap_changing)711 ssize_t mfill_zeropage(struct mm_struct *dst_mm, unsigned long start,
712 unsigned long len, atomic_t *mmap_changing)
713 {
714 return __mcopy_atomic(dst_mm, start, 0, len, MCOPY_ATOMIC_ZEROPAGE,
715 mmap_changing, 0);
716 }
717
mcopy_continue(struct mm_struct * dst_mm,unsigned long start,unsigned long len,atomic_t * mmap_changing)718 ssize_t mcopy_continue(struct mm_struct *dst_mm, unsigned long start,
719 unsigned long len, atomic_t *mmap_changing)
720 {
721 return __mcopy_atomic(dst_mm, start, 0, len, MCOPY_ATOMIC_CONTINUE,
722 mmap_changing, 0);
723 }
724
uffd_wp_range(struct mm_struct * dst_mm,struct vm_area_struct * dst_vma,unsigned long start,unsigned long len,bool enable_wp)725 void uffd_wp_range(struct mm_struct *dst_mm, struct vm_area_struct *dst_vma,
726 unsigned long start, unsigned long len, bool enable_wp)
727 {
728 struct mmu_gather tlb;
729 pgprot_t newprot;
730
731 if (enable_wp)
732 newprot = vm_get_page_prot(dst_vma->vm_flags & ~(VM_WRITE));
733 else
734 newprot = vm_get_page_prot(dst_vma->vm_flags);
735
736 tlb_gather_mmu(&tlb, dst_mm);
737 change_protection(&tlb, dst_vma, start, start + len, newprot,
738 enable_wp ? MM_CP_UFFD_WP : MM_CP_UFFD_WP_RESOLVE);
739 tlb_finish_mmu(&tlb);
740 }
741
mwriteprotect_range(struct mm_struct * dst_mm,unsigned long start,unsigned long len,bool enable_wp,atomic_t * mmap_changing)742 int mwriteprotect_range(struct mm_struct *dst_mm, unsigned long start,
743 unsigned long len, bool enable_wp,
744 atomic_t *mmap_changing)
745 {
746 struct vm_area_struct *dst_vma;
747 unsigned long page_mask;
748 int err;
749
750 /*
751 * Sanitize the command parameters:
752 */
753 BUG_ON(start & ~PAGE_MASK);
754 BUG_ON(len & ~PAGE_MASK);
755
756 /* Does the address range wrap, or is the span zero-sized? */
757 BUG_ON(start + len <= start);
758
759 mmap_read_lock(dst_mm);
760
761 /*
762 * If memory mappings are changing because of non-cooperative
763 * operation (e.g. mremap) running in parallel, bail out and
764 * request the user to retry later
765 */
766 err = -EAGAIN;
767 if (mmap_changing && atomic_read(mmap_changing))
768 goto out_unlock;
769
770 err = -ENOENT;
771 dst_vma = find_dst_vma(dst_mm, start, len);
772
773 if (!dst_vma)
774 goto out_unlock;
775 if (!userfaultfd_wp(dst_vma))
776 goto out_unlock;
777 if (!vma_can_userfault(dst_vma, dst_vma->vm_flags))
778 goto out_unlock;
779
780 if (is_vm_hugetlb_page(dst_vma)) {
781 err = -EINVAL;
782 page_mask = vma_kernel_pagesize(dst_vma) - 1;
783 if ((start & page_mask) || (len & page_mask))
784 goto out_unlock;
785 }
786
787 uffd_wp_range(dst_mm, dst_vma, start, len, enable_wp);
788
789 err = 0;
790 out_unlock:
791 mmap_read_unlock(dst_mm);
792 return err;
793 }
794