1 | // SPDX-License-Identifier: GPL-2.0-only |
2 | /* |
3 | * mm/userfaultfd.c |
4 | * |
5 | * Copyright (C) 2015 Red Hat, Inc. |
6 | */ |
7 | |
8 | #include <linux/mm.h> |
9 | #include <linux/sched/signal.h> |
10 | #include <linux/pagemap.h> |
11 | #include <linux/rmap.h> |
12 | #include <linux/swap.h> |
13 | #include <linux/swapops.h> |
14 | #include <linux/userfaultfd_k.h> |
15 | #include <linux/mmu_notifier.h> |
16 | #include <linux/hugetlb.h> |
17 | #include <linux/shmem_fs.h> |
18 | #include <asm/tlbflush.h> |
19 | #include <asm/tlb.h> |
20 | #include "internal.h" |
21 | |
22 | static __always_inline |
23 | struct vm_area_struct *find_dst_vma(struct mm_struct *dst_mm, |
24 | unsigned long dst_start, |
25 | unsigned long len) |
26 | { |
27 | /* |
28 | * Make sure that the dst range is both valid and fully within a |
29 | * single existing vma. |
30 | */ |
31 | struct vm_area_struct *dst_vma; |
32 | |
33 | dst_vma = find_vma(mm: dst_mm, addr: dst_start); |
34 | if (!range_in_vma(vma: dst_vma, start: dst_start, end: dst_start + len)) |
35 | return NULL; |
36 | |
37 | /* |
38 | * Check the vma is registered in uffd, this is required to |
39 | * enforce the VM_MAYWRITE check done at uffd registration |
40 | * time. |
41 | */ |
42 | if (!dst_vma->vm_userfaultfd_ctx.ctx) |
43 | return NULL; |
44 | |
45 | return dst_vma; |
46 | } |
47 | |
48 | /* Check if dst_addr is outside of file's size. Must be called with ptl held. */ |
49 | static bool mfill_file_over_size(struct vm_area_struct *dst_vma, |
50 | unsigned long dst_addr) |
51 | { |
52 | struct inode *inode; |
53 | pgoff_t offset, max_off; |
54 | |
55 | if (!dst_vma->vm_file) |
56 | return false; |
57 | |
58 | inode = dst_vma->vm_file->f_inode; |
59 | offset = linear_page_index(vma: dst_vma, address: dst_addr); |
60 | max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE); |
61 | return offset >= max_off; |
62 | } |
63 | |
64 | /* |
65 | * Install PTEs, to map dst_addr (within dst_vma) to page. |
66 | * |
67 | * This function handles both MCOPY_ATOMIC_NORMAL and _CONTINUE for both shmem |
68 | * and anon, and for both shared and private VMAs. |
69 | */ |
70 | int mfill_atomic_install_pte(pmd_t *dst_pmd, |
71 | struct vm_area_struct *dst_vma, |
72 | unsigned long dst_addr, struct page *page, |
73 | bool newly_allocated, uffd_flags_t flags) |
74 | { |
75 | int ret; |
76 | struct mm_struct *dst_mm = dst_vma->vm_mm; |
77 | pte_t _dst_pte, *dst_pte; |
78 | bool writable = dst_vma->vm_flags & VM_WRITE; |
79 | bool vm_shared = dst_vma->vm_flags & VM_SHARED; |
80 | bool page_in_cache = page_mapping(page); |
81 | spinlock_t *ptl; |
82 | struct folio *folio; |
83 | |
84 | _dst_pte = mk_pte(page, dst_vma->vm_page_prot); |
85 | _dst_pte = pte_mkdirty(pte: _dst_pte); |
86 | if (page_in_cache && !vm_shared) |
87 | writable = false; |
88 | if (writable) |
89 | _dst_pte = pte_mkwrite(pte: _dst_pte, vma: dst_vma); |
90 | if (flags & MFILL_ATOMIC_WP) |
91 | _dst_pte = pte_mkuffd_wp(pte: _dst_pte); |
92 | |
93 | ret = -EAGAIN; |
94 | dst_pte = pte_offset_map_lock(mm: dst_mm, pmd: dst_pmd, addr: dst_addr, ptlp: &ptl); |
95 | if (!dst_pte) |
96 | goto out; |
97 | |
98 | if (mfill_file_over_size(dst_vma, dst_addr)) { |
99 | ret = -EFAULT; |
100 | goto out_unlock; |
101 | } |
102 | |
103 | ret = -EEXIST; |
104 | /* |
105 | * We allow to overwrite a pte marker: consider when both MISSING|WP |
106 | * registered, we firstly wr-protect a none pte which has no page cache |
107 | * page backing it, then access the page. |
108 | */ |
109 | if (!pte_none_mostly(pte: ptep_get(ptep: dst_pte))) |
110 | goto out_unlock; |
111 | |
112 | folio = page_folio(page); |
113 | if (page_in_cache) { |
114 | /* Usually, cache pages are already added to LRU */ |
115 | if (newly_allocated) |
116 | folio_add_lru(folio); |
117 | page_add_file_rmap(page, dst_vma, compound: false); |
118 | } else { |
119 | page_add_new_anon_rmap(page, dst_vma, address: dst_addr); |
120 | folio_add_lru_vma(folio, dst_vma); |
121 | } |
122 | |
123 | /* |
124 | * Must happen after rmap, as mm_counter() checks mapping (via |
125 | * PageAnon()), which is set by __page_set_anon_rmap(). |
126 | */ |
127 | inc_mm_counter(mm: dst_mm, member: mm_counter(page)); |
128 | |
129 | set_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte); |
130 | |
131 | /* No need to invalidate - it was non-present before */ |
132 | update_mmu_cache(vma: dst_vma, addr: dst_addr, ptep: dst_pte); |
133 | ret = 0; |
134 | out_unlock: |
135 | pte_unmap_unlock(dst_pte, ptl); |
136 | out: |
137 | return ret; |
138 | } |
139 | |
140 | static int mfill_atomic_pte_copy(pmd_t *dst_pmd, |
141 | struct vm_area_struct *dst_vma, |
142 | unsigned long dst_addr, |
143 | unsigned long src_addr, |
144 | uffd_flags_t flags, |
145 | struct folio **foliop) |
146 | { |
147 | void *kaddr; |
148 | int ret; |
149 | struct folio *folio; |
150 | |
151 | if (!*foliop) { |
152 | ret = -ENOMEM; |
153 | folio = vma_alloc_folio(GFP_HIGHUSER_MOVABLE, order: 0, vma: dst_vma, |
154 | addr: dst_addr, hugepage: false); |
155 | if (!folio) |
156 | goto out; |
157 | |
158 | kaddr = kmap_local_folio(folio, offset: 0); |
159 | /* |
160 | * The read mmap_lock is held here. Despite the |
161 | * mmap_lock being read recursive a deadlock is still |
162 | * possible if a writer has taken a lock. For example: |
163 | * |
164 | * process A thread 1 takes read lock on own mmap_lock |
165 | * process A thread 2 calls mmap, blocks taking write lock |
166 | * process B thread 1 takes page fault, read lock on own mmap lock |
167 | * process B thread 2 calls mmap, blocks taking write lock |
168 | * process A thread 1 blocks taking read lock on process B |
169 | * process B thread 1 blocks taking read lock on process A |
170 | * |
171 | * Disable page faults to prevent potential deadlock |
172 | * and retry the copy outside the mmap_lock. |
173 | */ |
174 | pagefault_disable(); |
175 | ret = copy_from_user(to: kaddr, from: (const void __user *) src_addr, |
176 | PAGE_SIZE); |
177 | pagefault_enable(); |
178 | kunmap_local(kaddr); |
179 | |
180 | /* fallback to copy_from_user outside mmap_lock */ |
181 | if (unlikely(ret)) { |
182 | ret = -ENOENT; |
183 | *foliop = folio; |
184 | /* don't free the page */ |
185 | goto out; |
186 | } |
187 | |
188 | flush_dcache_folio(folio); |
189 | } else { |
190 | folio = *foliop; |
191 | *foliop = NULL; |
192 | } |
193 | |
194 | /* |
195 | * The memory barrier inside __folio_mark_uptodate makes sure that |
196 | * preceding stores to the page contents become visible before |
197 | * the set_pte_at() write. |
198 | */ |
199 | __folio_mark_uptodate(folio); |
200 | |
201 | ret = -ENOMEM; |
202 | if (mem_cgroup_charge(folio, mm: dst_vma->vm_mm, GFP_KERNEL)) |
203 | goto out_release; |
204 | |
205 | ret = mfill_atomic_install_pte(dst_pmd, dst_vma, dst_addr, |
206 | page: &folio->page, newly_allocated: true, flags); |
207 | if (ret) |
208 | goto out_release; |
209 | out: |
210 | return ret; |
211 | out_release: |
212 | folio_put(folio); |
213 | goto out; |
214 | } |
215 | |
216 | static int mfill_atomic_pte_zeropage(pmd_t *dst_pmd, |
217 | struct vm_area_struct *dst_vma, |
218 | unsigned long dst_addr) |
219 | { |
220 | pte_t _dst_pte, *dst_pte; |
221 | spinlock_t *ptl; |
222 | int ret; |
223 | |
224 | _dst_pte = pte_mkspecial(pte: pfn_pte(page_nr: my_zero_pfn(addr: dst_addr), |
225 | pgprot: dst_vma->vm_page_prot)); |
226 | ret = -EAGAIN; |
227 | dst_pte = pte_offset_map_lock(mm: dst_vma->vm_mm, pmd: dst_pmd, addr: dst_addr, ptlp: &ptl); |
228 | if (!dst_pte) |
229 | goto out; |
230 | if (mfill_file_over_size(dst_vma, dst_addr)) { |
231 | ret = -EFAULT; |
232 | goto out_unlock; |
233 | } |
234 | ret = -EEXIST; |
235 | if (!pte_none(pte: ptep_get(ptep: dst_pte))) |
236 | goto out_unlock; |
237 | set_pte_at(dst_vma->vm_mm, dst_addr, dst_pte, _dst_pte); |
238 | /* No need to invalidate - it was non-present before */ |
239 | update_mmu_cache(vma: dst_vma, addr: dst_addr, ptep: dst_pte); |
240 | ret = 0; |
241 | out_unlock: |
242 | pte_unmap_unlock(dst_pte, ptl); |
243 | out: |
244 | return ret; |
245 | } |
246 | |
247 | /* Handles UFFDIO_CONTINUE for all shmem VMAs (shared or private). */ |
248 | static int mfill_atomic_pte_continue(pmd_t *dst_pmd, |
249 | struct vm_area_struct *dst_vma, |
250 | unsigned long dst_addr, |
251 | uffd_flags_t flags) |
252 | { |
253 | struct inode *inode = file_inode(f: dst_vma->vm_file); |
254 | pgoff_t pgoff = linear_page_index(vma: dst_vma, address: dst_addr); |
255 | struct folio *folio; |
256 | struct page *page; |
257 | int ret; |
258 | |
259 | ret = shmem_get_folio(inode, index: pgoff, foliop: &folio, sgp: SGP_NOALLOC); |
260 | /* Our caller expects us to return -EFAULT if we failed to find folio */ |
261 | if (ret == -ENOENT) |
262 | ret = -EFAULT; |
263 | if (ret) |
264 | goto out; |
265 | if (!folio) { |
266 | ret = -EFAULT; |
267 | goto out; |
268 | } |
269 | |
270 | page = folio_file_page(folio, index: pgoff); |
271 | if (PageHWPoison(page)) { |
272 | ret = -EIO; |
273 | goto out_release; |
274 | } |
275 | |
276 | ret = mfill_atomic_install_pte(dst_pmd, dst_vma, dst_addr, |
277 | page, newly_allocated: false, flags); |
278 | if (ret) |
279 | goto out_release; |
280 | |
281 | folio_unlock(folio); |
282 | ret = 0; |
283 | out: |
284 | return ret; |
285 | out_release: |
286 | folio_unlock(folio); |
287 | folio_put(folio); |
288 | goto out; |
289 | } |
290 | |
291 | /* Handles UFFDIO_POISON for all non-hugetlb VMAs. */ |
292 | static int mfill_atomic_pte_poison(pmd_t *dst_pmd, |
293 | struct vm_area_struct *dst_vma, |
294 | unsigned long dst_addr, |
295 | uffd_flags_t flags) |
296 | { |
297 | int ret; |
298 | struct mm_struct *dst_mm = dst_vma->vm_mm; |
299 | pte_t _dst_pte, *dst_pte; |
300 | spinlock_t *ptl; |
301 | |
302 | _dst_pte = make_pte_marker(PTE_MARKER_POISONED); |
303 | ret = -EAGAIN; |
304 | dst_pte = pte_offset_map_lock(mm: dst_mm, pmd: dst_pmd, addr: dst_addr, ptlp: &ptl); |
305 | if (!dst_pte) |
306 | goto out; |
307 | |
308 | if (mfill_file_over_size(dst_vma, dst_addr)) { |
309 | ret = -EFAULT; |
310 | goto out_unlock; |
311 | } |
312 | |
313 | ret = -EEXIST; |
314 | /* Refuse to overwrite any PTE, even a PTE marker (e.g. UFFD WP). */ |
315 | if (!pte_none(pte: *dst_pte)) |
316 | goto out_unlock; |
317 | |
318 | set_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte); |
319 | |
320 | /* No need to invalidate - it was non-present before */ |
321 | update_mmu_cache(vma: dst_vma, addr: dst_addr, ptep: dst_pte); |
322 | ret = 0; |
323 | out_unlock: |
324 | pte_unmap_unlock(dst_pte, ptl); |
325 | out: |
326 | return ret; |
327 | } |
328 | |
329 | static pmd_t *mm_alloc_pmd(struct mm_struct *mm, unsigned long address) |
330 | { |
331 | pgd_t *pgd; |
332 | p4d_t *p4d; |
333 | pud_t *pud; |
334 | |
335 | pgd = pgd_offset(mm, address); |
336 | p4d = p4d_alloc(mm, pgd, address); |
337 | if (!p4d) |
338 | return NULL; |
339 | pud = pud_alloc(mm, p4d, address); |
340 | if (!pud) |
341 | return NULL; |
342 | /* |
343 | * Note that we didn't run this because the pmd was |
344 | * missing, the *pmd may be already established and in |
345 | * turn it may also be a trans_huge_pmd. |
346 | */ |
347 | return pmd_alloc(mm, pud, address); |
348 | } |
349 | |
350 | #ifdef CONFIG_HUGETLB_PAGE |
351 | /* |
352 | * mfill_atomic processing for HUGETLB vmas. Note that this routine is |
353 | * called with mmap_lock held, it will release mmap_lock before returning. |
354 | */ |
355 | static __always_inline ssize_t mfill_atomic_hugetlb( |
356 | struct vm_area_struct *dst_vma, |
357 | unsigned long dst_start, |
358 | unsigned long src_start, |
359 | unsigned long len, |
360 | uffd_flags_t flags) |
361 | { |
362 | struct mm_struct *dst_mm = dst_vma->vm_mm; |
363 | int vm_shared = dst_vma->vm_flags & VM_SHARED; |
364 | ssize_t err; |
365 | pte_t *dst_pte; |
366 | unsigned long src_addr, dst_addr; |
367 | long copied; |
368 | struct folio *folio; |
369 | unsigned long vma_hpagesize; |
370 | pgoff_t idx; |
371 | u32 hash; |
372 | struct address_space *mapping; |
373 | |
374 | /* |
375 | * There is no default zero huge page for all huge page sizes as |
376 | * supported by hugetlb. A PMD_SIZE huge pages may exist as used |
377 | * by THP. Since we can not reliably insert a zero page, this |
378 | * feature is not supported. |
379 | */ |
380 | if (uffd_flags_mode_is(flags, expected: MFILL_ATOMIC_ZEROPAGE)) { |
381 | mmap_read_unlock(mm: dst_mm); |
382 | return -EINVAL; |
383 | } |
384 | |
385 | src_addr = src_start; |
386 | dst_addr = dst_start; |
387 | copied = 0; |
388 | folio = NULL; |
389 | vma_hpagesize = vma_kernel_pagesize(vma: dst_vma); |
390 | |
391 | /* |
392 | * Validate alignment based on huge page size |
393 | */ |
394 | err = -EINVAL; |
395 | if (dst_start & (vma_hpagesize - 1) || len & (vma_hpagesize - 1)) |
396 | goto out_unlock; |
397 | |
398 | retry: |
399 | /* |
400 | * On routine entry dst_vma is set. If we had to drop mmap_lock and |
401 | * retry, dst_vma will be set to NULL and we must lookup again. |
402 | */ |
403 | if (!dst_vma) { |
404 | err = -ENOENT; |
405 | dst_vma = find_dst_vma(dst_mm, dst_start, len); |
406 | if (!dst_vma || !is_vm_hugetlb_page(vma: dst_vma)) |
407 | goto out_unlock; |
408 | |
409 | err = -EINVAL; |
410 | if (vma_hpagesize != vma_kernel_pagesize(vma: dst_vma)) |
411 | goto out_unlock; |
412 | |
413 | vm_shared = dst_vma->vm_flags & VM_SHARED; |
414 | } |
415 | |
416 | /* |
417 | * If not shared, ensure the dst_vma has a anon_vma. |
418 | */ |
419 | err = -ENOMEM; |
420 | if (!vm_shared) { |
421 | if (unlikely(anon_vma_prepare(dst_vma))) |
422 | goto out_unlock; |
423 | } |
424 | |
425 | while (src_addr < src_start + len) { |
426 | BUG_ON(dst_addr >= dst_start + len); |
427 | |
428 | /* |
429 | * Serialize via vma_lock and hugetlb_fault_mutex. |
430 | * vma_lock ensures the dst_pte remains valid even |
431 | * in the case of shared pmds. fault mutex prevents |
432 | * races with other faulting threads. |
433 | */ |
434 | idx = linear_page_index(vma: dst_vma, address: dst_addr); |
435 | mapping = dst_vma->vm_file->f_mapping; |
436 | hash = hugetlb_fault_mutex_hash(mapping, idx); |
437 | mutex_lock(&hugetlb_fault_mutex_table[hash]); |
438 | hugetlb_vma_lock_read(vma: dst_vma); |
439 | |
440 | err = -ENOMEM; |
441 | dst_pte = huge_pte_alloc(mm: dst_mm, vma: dst_vma, addr: dst_addr, sz: vma_hpagesize); |
442 | if (!dst_pte) { |
443 | hugetlb_vma_unlock_read(vma: dst_vma); |
444 | mutex_unlock(lock: &hugetlb_fault_mutex_table[hash]); |
445 | goto out_unlock; |
446 | } |
447 | |
448 | if (!uffd_flags_mode_is(flags, expected: MFILL_ATOMIC_CONTINUE) && |
449 | !huge_pte_none_mostly(pte: huge_ptep_get(ptep: dst_pte))) { |
450 | err = -EEXIST; |
451 | hugetlb_vma_unlock_read(vma: dst_vma); |
452 | mutex_unlock(lock: &hugetlb_fault_mutex_table[hash]); |
453 | goto out_unlock; |
454 | } |
455 | |
456 | err = hugetlb_mfill_atomic_pte(dst_pte, dst_vma, dst_addr, |
457 | src_addr, flags, foliop: &folio); |
458 | |
459 | hugetlb_vma_unlock_read(vma: dst_vma); |
460 | mutex_unlock(lock: &hugetlb_fault_mutex_table[hash]); |
461 | |
462 | cond_resched(); |
463 | |
464 | if (unlikely(err == -ENOENT)) { |
465 | mmap_read_unlock(mm: dst_mm); |
466 | BUG_ON(!folio); |
467 | |
468 | err = copy_folio_from_user(dst_folio: folio, |
469 | usr_src: (const void __user *)src_addr, allow_pagefault: true); |
470 | if (unlikely(err)) { |
471 | err = -EFAULT; |
472 | goto out; |
473 | } |
474 | mmap_read_lock(mm: dst_mm); |
475 | |
476 | dst_vma = NULL; |
477 | goto retry; |
478 | } else |
479 | BUG_ON(folio); |
480 | |
481 | if (!err) { |
482 | dst_addr += vma_hpagesize; |
483 | src_addr += vma_hpagesize; |
484 | copied += vma_hpagesize; |
485 | |
486 | if (fatal_signal_pending(current)) |
487 | err = -EINTR; |
488 | } |
489 | if (err) |
490 | break; |
491 | } |
492 | |
493 | out_unlock: |
494 | mmap_read_unlock(mm: dst_mm); |
495 | out: |
496 | if (folio) |
497 | folio_put(folio); |
498 | BUG_ON(copied < 0); |
499 | BUG_ON(err > 0); |
500 | BUG_ON(!copied && !err); |
501 | return copied ? copied : err; |
502 | } |
503 | #else /* !CONFIG_HUGETLB_PAGE */ |
504 | /* fail at build time if gcc attempts to use this */ |
505 | extern ssize_t mfill_atomic_hugetlb(struct vm_area_struct *dst_vma, |
506 | unsigned long dst_start, |
507 | unsigned long src_start, |
508 | unsigned long len, |
509 | uffd_flags_t flags); |
510 | #endif /* CONFIG_HUGETLB_PAGE */ |
511 | |
512 | static __always_inline ssize_t mfill_atomic_pte(pmd_t *dst_pmd, |
513 | struct vm_area_struct *dst_vma, |
514 | unsigned long dst_addr, |
515 | unsigned long src_addr, |
516 | uffd_flags_t flags, |
517 | struct folio **foliop) |
518 | { |
519 | ssize_t err; |
520 | |
521 | if (uffd_flags_mode_is(flags, expected: MFILL_ATOMIC_CONTINUE)) { |
522 | return mfill_atomic_pte_continue(dst_pmd, dst_vma, |
523 | dst_addr, flags); |
524 | } else if (uffd_flags_mode_is(flags, expected: MFILL_ATOMIC_POISON)) { |
525 | return mfill_atomic_pte_poison(dst_pmd, dst_vma, |
526 | dst_addr, flags); |
527 | } |
528 | |
529 | /* |
530 | * The normal page fault path for a shmem will invoke the |
531 | * fault, fill the hole in the file and COW it right away. The |
532 | * result generates plain anonymous memory. So when we are |
533 | * asked to fill an hole in a MAP_PRIVATE shmem mapping, we'll |
534 | * generate anonymous memory directly without actually filling |
535 | * the hole. For the MAP_PRIVATE case the robustness check |
536 | * only happens in the pagetable (to verify it's still none) |
537 | * and not in the radix tree. |
538 | */ |
539 | if (!(dst_vma->vm_flags & VM_SHARED)) { |
540 | if (uffd_flags_mode_is(flags, expected: MFILL_ATOMIC_COPY)) |
541 | err = mfill_atomic_pte_copy(dst_pmd, dst_vma, |
542 | dst_addr, src_addr, |
543 | flags, foliop); |
544 | else |
545 | err = mfill_atomic_pte_zeropage(dst_pmd, |
546 | dst_vma, dst_addr); |
547 | } else { |
548 | err = shmem_mfill_atomic_pte(dst_pmd, dst_vma, |
549 | dst_addr, src_addr, |
550 | flags, foliop); |
551 | } |
552 | |
553 | return err; |
554 | } |
555 | |
556 | static __always_inline ssize_t mfill_atomic(struct mm_struct *dst_mm, |
557 | unsigned long dst_start, |
558 | unsigned long src_start, |
559 | unsigned long len, |
560 | atomic_t *mmap_changing, |
561 | uffd_flags_t flags) |
562 | { |
563 | struct vm_area_struct *dst_vma; |
564 | ssize_t err; |
565 | pmd_t *dst_pmd; |
566 | unsigned long src_addr, dst_addr; |
567 | long copied; |
568 | struct folio *folio; |
569 | |
570 | /* |
571 | * Sanitize the command parameters: |
572 | */ |
573 | BUG_ON(dst_start & ~PAGE_MASK); |
574 | BUG_ON(len & ~PAGE_MASK); |
575 | |
576 | /* Does the address range wrap, or is the span zero-sized? */ |
577 | BUG_ON(src_start + len <= src_start); |
578 | BUG_ON(dst_start + len <= dst_start); |
579 | |
580 | src_addr = src_start; |
581 | dst_addr = dst_start; |
582 | copied = 0; |
583 | folio = NULL; |
584 | retry: |
585 | mmap_read_lock(mm: dst_mm); |
586 | |
587 | /* |
588 | * If memory mappings are changing because of non-cooperative |
589 | * operation (e.g. mremap) running in parallel, bail out and |
590 | * request the user to retry later |
591 | */ |
592 | err = -EAGAIN; |
593 | if (mmap_changing && atomic_read(v: mmap_changing)) |
594 | goto out_unlock; |
595 | |
596 | /* |
597 | * Make sure the vma is not shared, that the dst range is |
598 | * both valid and fully within a single existing vma. |
599 | */ |
600 | err = -ENOENT; |
601 | dst_vma = find_dst_vma(dst_mm, dst_start, len); |
602 | if (!dst_vma) |
603 | goto out_unlock; |
604 | |
605 | err = -EINVAL; |
606 | /* |
607 | * shmem_zero_setup is invoked in mmap for MAP_ANONYMOUS|MAP_SHARED but |
608 | * it will overwrite vm_ops, so vma_is_anonymous must return false. |
609 | */ |
610 | if (WARN_ON_ONCE(vma_is_anonymous(dst_vma) && |
611 | dst_vma->vm_flags & VM_SHARED)) |
612 | goto out_unlock; |
613 | |
614 | /* |
615 | * validate 'mode' now that we know the dst_vma: don't allow |
616 | * a wrprotect copy if the userfaultfd didn't register as WP. |
617 | */ |
618 | if ((flags & MFILL_ATOMIC_WP) && !(dst_vma->vm_flags & VM_UFFD_WP)) |
619 | goto out_unlock; |
620 | |
621 | /* |
622 | * If this is a HUGETLB vma, pass off to appropriate routine |
623 | */ |
624 | if (is_vm_hugetlb_page(vma: dst_vma)) |
625 | return mfill_atomic_hugetlb(dst_vma, dst_start, |
626 | src_start, len, flags); |
627 | |
628 | if (!vma_is_anonymous(vma: dst_vma) && !vma_is_shmem(vma: dst_vma)) |
629 | goto out_unlock; |
630 | if (!vma_is_shmem(vma: dst_vma) && |
631 | uffd_flags_mode_is(flags, expected: MFILL_ATOMIC_CONTINUE)) |
632 | goto out_unlock; |
633 | |
634 | /* |
635 | * Ensure the dst_vma has a anon_vma or this page |
636 | * would get a NULL anon_vma when moved in the |
637 | * dst_vma. |
638 | */ |
639 | err = -ENOMEM; |
640 | if (!(dst_vma->vm_flags & VM_SHARED) && |
641 | unlikely(anon_vma_prepare(dst_vma))) |
642 | goto out_unlock; |
643 | |
644 | while (src_addr < src_start + len) { |
645 | pmd_t dst_pmdval; |
646 | |
647 | BUG_ON(dst_addr >= dst_start + len); |
648 | |
649 | dst_pmd = mm_alloc_pmd(mm: dst_mm, address: dst_addr); |
650 | if (unlikely(!dst_pmd)) { |
651 | err = -ENOMEM; |
652 | break; |
653 | } |
654 | |
655 | dst_pmdval = pmdp_get_lockless(pmdp: dst_pmd); |
656 | /* |
657 | * If the dst_pmd is mapped as THP don't |
658 | * override it and just be strict. |
659 | */ |
660 | if (unlikely(pmd_trans_huge(dst_pmdval))) { |
661 | err = -EEXIST; |
662 | break; |
663 | } |
664 | if (unlikely(pmd_none(dst_pmdval)) && |
665 | unlikely(__pte_alloc(dst_mm, dst_pmd))) { |
666 | err = -ENOMEM; |
667 | break; |
668 | } |
669 | /* If an huge pmd materialized from under us fail */ |
670 | if (unlikely(pmd_trans_huge(*dst_pmd))) { |
671 | err = -EFAULT; |
672 | break; |
673 | } |
674 | |
675 | BUG_ON(pmd_none(*dst_pmd)); |
676 | BUG_ON(pmd_trans_huge(*dst_pmd)); |
677 | |
678 | err = mfill_atomic_pte(dst_pmd, dst_vma, dst_addr, |
679 | src_addr, flags, foliop: &folio); |
680 | cond_resched(); |
681 | |
682 | if (unlikely(err == -ENOENT)) { |
683 | void *kaddr; |
684 | |
685 | mmap_read_unlock(mm: dst_mm); |
686 | BUG_ON(!folio); |
687 | |
688 | kaddr = kmap_local_folio(folio, offset: 0); |
689 | err = copy_from_user(to: kaddr, |
690 | from: (const void __user *) src_addr, |
691 | PAGE_SIZE); |
692 | kunmap_local(kaddr); |
693 | if (unlikely(err)) { |
694 | err = -EFAULT; |
695 | goto out; |
696 | } |
697 | flush_dcache_folio(folio); |
698 | goto retry; |
699 | } else |
700 | BUG_ON(folio); |
701 | |
702 | if (!err) { |
703 | dst_addr += PAGE_SIZE; |
704 | src_addr += PAGE_SIZE; |
705 | copied += PAGE_SIZE; |
706 | |
707 | if (fatal_signal_pending(current)) |
708 | err = -EINTR; |
709 | } |
710 | if (err) |
711 | break; |
712 | } |
713 | |
714 | out_unlock: |
715 | mmap_read_unlock(mm: dst_mm); |
716 | out: |
717 | if (folio) |
718 | folio_put(folio); |
719 | BUG_ON(copied < 0); |
720 | BUG_ON(err > 0); |
721 | BUG_ON(!copied && !err); |
722 | return copied ? copied : err; |
723 | } |
724 | |
725 | ssize_t mfill_atomic_copy(struct mm_struct *dst_mm, unsigned long dst_start, |
726 | unsigned long src_start, unsigned long len, |
727 | atomic_t *mmap_changing, uffd_flags_t flags) |
728 | { |
729 | return mfill_atomic(dst_mm, dst_start, src_start, len, mmap_changing, |
730 | flags: uffd_flags_set_mode(flags, mode: MFILL_ATOMIC_COPY)); |
731 | } |
732 | |
733 | ssize_t mfill_atomic_zeropage(struct mm_struct *dst_mm, unsigned long start, |
734 | unsigned long len, atomic_t *mmap_changing) |
735 | { |
736 | return mfill_atomic(dst_mm, dst_start: start, src_start: 0, len, mmap_changing, |
737 | flags: uffd_flags_set_mode(flags: 0, mode: MFILL_ATOMIC_ZEROPAGE)); |
738 | } |
739 | |
740 | ssize_t mfill_atomic_continue(struct mm_struct *dst_mm, unsigned long start, |
741 | unsigned long len, atomic_t *mmap_changing, |
742 | uffd_flags_t flags) |
743 | { |
744 | return mfill_atomic(dst_mm, dst_start: start, src_start: 0, len, mmap_changing, |
745 | flags: uffd_flags_set_mode(flags, mode: MFILL_ATOMIC_CONTINUE)); |
746 | } |
747 | |
748 | ssize_t mfill_atomic_poison(struct mm_struct *dst_mm, unsigned long start, |
749 | unsigned long len, atomic_t *mmap_changing, |
750 | uffd_flags_t flags) |
751 | { |
752 | return mfill_atomic(dst_mm, dst_start: start, src_start: 0, len, mmap_changing, |
753 | flags: uffd_flags_set_mode(flags, mode: MFILL_ATOMIC_POISON)); |
754 | } |
755 | |
756 | long uffd_wp_range(struct vm_area_struct *dst_vma, |
757 | unsigned long start, unsigned long len, bool enable_wp) |
758 | { |
759 | unsigned int mm_cp_flags; |
760 | struct mmu_gather tlb; |
761 | long ret; |
762 | |
763 | VM_WARN_ONCE(start < dst_vma->vm_start || start + len > dst_vma->vm_end, |
764 | "The address range exceeds VMA boundary.\n" ); |
765 | if (enable_wp) |
766 | mm_cp_flags = MM_CP_UFFD_WP; |
767 | else |
768 | mm_cp_flags = MM_CP_UFFD_WP_RESOLVE; |
769 | |
770 | /* |
771 | * vma->vm_page_prot already reflects that uffd-wp is enabled for this |
772 | * VMA (see userfaultfd_set_vm_flags()) and that all PTEs are supposed |
773 | * to be write-protected as default whenever protection changes. |
774 | * Try upgrading write permissions manually. |
775 | */ |
776 | if (!enable_wp && vma_wants_manual_pte_write_upgrade(vma: dst_vma)) |
777 | mm_cp_flags |= MM_CP_TRY_CHANGE_WRITABLE; |
778 | tlb_gather_mmu(tlb: &tlb, mm: dst_vma->vm_mm); |
779 | ret = change_protection(tlb: &tlb, vma: dst_vma, start, end: start + len, cp_flags: mm_cp_flags); |
780 | tlb_finish_mmu(tlb: &tlb); |
781 | |
782 | return ret; |
783 | } |
784 | |
785 | int mwriteprotect_range(struct mm_struct *dst_mm, unsigned long start, |
786 | unsigned long len, bool enable_wp, |
787 | atomic_t *mmap_changing) |
788 | { |
789 | unsigned long end = start + len; |
790 | unsigned long _start, _end; |
791 | struct vm_area_struct *dst_vma; |
792 | unsigned long page_mask; |
793 | long err; |
794 | VMA_ITERATOR(vmi, dst_mm, start); |
795 | |
796 | /* |
797 | * Sanitize the command parameters: |
798 | */ |
799 | BUG_ON(start & ~PAGE_MASK); |
800 | BUG_ON(len & ~PAGE_MASK); |
801 | |
802 | /* Does the address range wrap, or is the span zero-sized? */ |
803 | BUG_ON(start + len <= start); |
804 | |
805 | mmap_read_lock(mm: dst_mm); |
806 | |
807 | /* |
808 | * If memory mappings are changing because of non-cooperative |
809 | * operation (e.g. mremap) running in parallel, bail out and |
810 | * request the user to retry later |
811 | */ |
812 | err = -EAGAIN; |
813 | if (mmap_changing && atomic_read(v: mmap_changing)) |
814 | goto out_unlock; |
815 | |
816 | err = -ENOENT; |
817 | for_each_vma_range(vmi, dst_vma, end) { |
818 | |
819 | if (!userfaultfd_wp(vma: dst_vma)) { |
820 | err = -ENOENT; |
821 | break; |
822 | } |
823 | |
824 | if (is_vm_hugetlb_page(vma: dst_vma)) { |
825 | err = -EINVAL; |
826 | page_mask = vma_kernel_pagesize(vma: dst_vma) - 1; |
827 | if ((start & page_mask) || (len & page_mask)) |
828 | break; |
829 | } |
830 | |
831 | _start = max(dst_vma->vm_start, start); |
832 | _end = min(dst_vma->vm_end, end); |
833 | |
834 | err = uffd_wp_range(dst_vma, start: _start, len: _end - _start, enable_wp); |
835 | |
836 | /* Return 0 on success, <0 on failures */ |
837 | if (err < 0) |
838 | break; |
839 | err = 0; |
840 | } |
841 | out_unlock: |
842 | mmap_read_unlock(mm: dst_mm); |
843 | return err; |
844 | } |
845 | |