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Merge tag 'io_uring-5.14-2021-07-09' of git://git.kernel.dk/linux-block
[mirror_ubuntu-jammy-kernel.git] / lib / iov_iter.c
1 // SPDX-License-Identifier: GPL-2.0-only
2 #include <crypto/hash.h>
3 #include <linux/export.h>
4 #include <linux/bvec.h>
5 #include <linux/fault-inject-usercopy.h>
6 #include <linux/uio.h>
7 #include <linux/pagemap.h>
8 #include <linux/highmem.h>
9 #include <linux/slab.h>
10 #include <linux/vmalloc.h>
11 #include <linux/splice.h>
12 #include <linux/compat.h>
13 #include <net/checksum.h>
14 #include <linux/scatterlist.h>
15 #include <linux/instrumented.h>
16
17 #define PIPE_PARANOIA /* for now */
18
19 /* covers iovec and kvec alike */
20 #define iterate_iovec(i, n, base, len, off, __p, STEP) { \
21 size_t off = 0; \
22 size_t skip = i->iov_offset; \
23 do { \
24 len = min(n, __p->iov_len - skip); \
25 if (likely(len)) { \
26 base = __p->iov_base + skip; \
27 len -= (STEP); \
28 off += len; \
29 skip += len; \
30 n -= len; \
31 if (skip < __p->iov_len) \
32 break; \
33 } \
34 __p++; \
35 skip = 0; \
36 } while (n); \
37 i->iov_offset = skip; \
38 n = off; \
39 }
40
41 #define iterate_bvec(i, n, base, len, off, p, STEP) { \
42 size_t off = 0; \
43 unsigned skip = i->iov_offset; \
44 while (n) { \
45 unsigned offset = p->bv_offset + skip; \
46 unsigned left; \
47 void *kaddr = kmap_local_page(p->bv_page + \
48 offset / PAGE_SIZE); \
49 base = kaddr + offset % PAGE_SIZE; \
50 len = min(min(n, (size_t)(p->bv_len - skip)), \
51 (size_t)(PAGE_SIZE - offset % PAGE_SIZE)); \
52 left = (STEP); \
53 kunmap_local(kaddr); \
54 len -= left; \
55 off += len; \
56 skip += len; \
57 if (skip == p->bv_len) { \
58 skip = 0; \
59 p++; \
60 } \
61 n -= len; \
62 if (left) \
63 break; \
64 } \
65 i->iov_offset = skip; \
66 n = off; \
67 }
68
69 #define iterate_xarray(i, n, base, len, __off, STEP) { \
70 __label__ __out; \
71 size_t __off = 0; \
72 struct page *head = NULL; \
73 loff_t start = i->xarray_start + i->iov_offset; \
74 unsigned offset = start % PAGE_SIZE; \
75 pgoff_t index = start / PAGE_SIZE; \
76 int j; \
77 \
78 XA_STATE(xas, i->xarray, index); \
79 \
80 rcu_read_lock(); \
81 xas_for_each(&xas, head, ULONG_MAX) { \
82 unsigned left; \
83 if (xas_retry(&xas, head)) \
84 continue; \
85 if (WARN_ON(xa_is_value(head))) \
86 break; \
87 if (WARN_ON(PageHuge(head))) \
88 break; \
89 for (j = (head->index < index) ? index - head->index : 0; \
90 j < thp_nr_pages(head); j++) { \
91 void *kaddr = kmap_local_page(head + j); \
92 base = kaddr + offset; \
93 len = PAGE_SIZE - offset; \
94 len = min(n, len); \
95 left = (STEP); \
96 kunmap_local(kaddr); \
97 len -= left; \
98 __off += len; \
99 n -= len; \
100 if (left || n == 0) \
101 goto __out; \
102 offset = 0; \
103 } \
104 } \
105 __out: \
106 rcu_read_unlock(); \
107 i->iov_offset += __off; \
108 n = __off; \
109 }
110
111 #define __iterate_and_advance(i, n, base, len, off, I, K) { \
112 if (unlikely(i->count < n)) \
113 n = i->count; \
114 if (likely(n)) { \
115 if (likely(iter_is_iovec(i))) { \
116 const struct iovec *iov = i->iov; \
117 void __user *base; \
118 size_t len; \
119 iterate_iovec(i, n, base, len, off, \
120 iov, (I)) \
121 i->nr_segs -= iov - i->iov; \
122 i->iov = iov; \
123 } else if (iov_iter_is_bvec(i)) { \
124 const struct bio_vec *bvec = i->bvec; \
125 void *base; \
126 size_t len; \
127 iterate_bvec(i, n, base, len, off, \
128 bvec, (K)) \
129 i->nr_segs -= bvec - i->bvec; \
130 i->bvec = bvec; \
131 } else if (iov_iter_is_kvec(i)) { \
132 const struct kvec *kvec = i->kvec; \
133 void *base; \
134 size_t len; \
135 iterate_iovec(i, n, base, len, off, \
136 kvec, (K)) \
137 i->nr_segs -= kvec - i->kvec; \
138 i->kvec = kvec; \
139 } else if (iov_iter_is_xarray(i)) { \
140 void *base; \
141 size_t len; \
142 iterate_xarray(i, n, base, len, off, \
143 (K)) \
144 } \
145 i->count -= n; \
146 } \
147 }
148 #define iterate_and_advance(i, n, base, len, off, I, K) \
149 __iterate_and_advance(i, n, base, len, off, I, ((void)(K),0))
150
151 static int copyout(void __user *to, const void *from, size_t n)
152 {
153 if (should_fail_usercopy())
154 return n;
155 if (access_ok(to, n)) {
156 instrument_copy_to_user(to, from, n);
157 n = raw_copy_to_user(to, from, n);
158 }
159 return n;
160 }
161
162 static int copyin(void *to, const void __user *from, size_t n)
163 {
164 if (should_fail_usercopy())
165 return n;
166 if (access_ok(from, n)) {
167 instrument_copy_from_user(to, from, n);
168 n = raw_copy_from_user(to, from, n);
169 }
170 return n;
171 }
172
173 static size_t copy_page_to_iter_iovec(struct page *page, size_t offset, size_t bytes,
174 struct iov_iter *i)
175 {
176 size_t skip, copy, left, wanted;
177 const struct iovec *iov;
178 char __user *buf;
179 void *kaddr, *from;
180
181 if (unlikely(bytes > i->count))
182 bytes = i->count;
183
184 if (unlikely(!bytes))
185 return 0;
186
187 might_fault();
188 wanted = bytes;
189 iov = i->iov;
190 skip = i->iov_offset;
191 buf = iov->iov_base + skip;
192 copy = min(bytes, iov->iov_len - skip);
193
194 if (IS_ENABLED(CONFIG_HIGHMEM) && !fault_in_pages_writeable(buf, copy)) {
195 kaddr = kmap_atomic(page);
196 from = kaddr + offset;
197
198 /* first chunk, usually the only one */
199 left = copyout(buf, from, copy);
200 copy -= left;
201 skip += copy;
202 from += copy;
203 bytes -= copy;
204
205 while (unlikely(!left && bytes)) {
206 iov++;
207 buf = iov->iov_base;
208 copy = min(bytes, iov->iov_len);
209 left = copyout(buf, from, copy);
210 copy -= left;
211 skip = copy;
212 from += copy;
213 bytes -= copy;
214 }
215 if (likely(!bytes)) {
216 kunmap_atomic(kaddr);
217 goto done;
218 }
219 offset = from - kaddr;
220 buf += copy;
221 kunmap_atomic(kaddr);
222 copy = min(bytes, iov->iov_len - skip);
223 }
224 /* Too bad - revert to non-atomic kmap */
225
226 kaddr = kmap(page);
227 from = kaddr + offset;
228 left = copyout(buf, from, copy);
229 copy -= left;
230 skip += copy;
231 from += copy;
232 bytes -= copy;
233 while (unlikely(!left && bytes)) {
234 iov++;
235 buf = iov->iov_base;
236 copy = min(bytes, iov->iov_len);
237 left = copyout(buf, from, copy);
238 copy -= left;
239 skip = copy;
240 from += copy;
241 bytes -= copy;
242 }
243 kunmap(page);
244
245 done:
246 if (skip == iov->iov_len) {
247 iov++;
248 skip = 0;
249 }
250 i->count -= wanted - bytes;
251 i->nr_segs -= iov - i->iov;
252 i->iov = iov;
253 i->iov_offset = skip;
254 return wanted - bytes;
255 }
256
257 static size_t copy_page_from_iter_iovec(struct page *page, size_t offset, size_t bytes,
258 struct iov_iter *i)
259 {
260 size_t skip, copy, left, wanted;
261 const struct iovec *iov;
262 char __user *buf;
263 void *kaddr, *to;
264
265 if (unlikely(bytes > i->count))
266 bytes = i->count;
267
268 if (unlikely(!bytes))
269 return 0;
270
271 might_fault();
272 wanted = bytes;
273 iov = i->iov;
274 skip = i->iov_offset;
275 buf = iov->iov_base + skip;
276 copy = min(bytes, iov->iov_len - skip);
277
278 if (IS_ENABLED(CONFIG_HIGHMEM) && !fault_in_pages_readable(buf, copy)) {
279 kaddr = kmap_atomic(page);
280 to = kaddr + offset;
281
282 /* first chunk, usually the only one */
283 left = copyin(to, buf, copy);
284 copy -= left;
285 skip += copy;
286 to += copy;
287 bytes -= copy;
288
289 while (unlikely(!left && bytes)) {
290 iov++;
291 buf = iov->iov_base;
292 copy = min(bytes, iov->iov_len);
293 left = copyin(to, buf, copy);
294 copy -= left;
295 skip = copy;
296 to += copy;
297 bytes -= copy;
298 }
299 if (likely(!bytes)) {
300 kunmap_atomic(kaddr);
301 goto done;
302 }
303 offset = to - kaddr;
304 buf += copy;
305 kunmap_atomic(kaddr);
306 copy = min(bytes, iov->iov_len - skip);
307 }
308 /* Too bad - revert to non-atomic kmap */
309
310 kaddr = kmap(page);
311 to = kaddr + offset;
312 left = copyin(to, buf, copy);
313 copy -= left;
314 skip += copy;
315 to += copy;
316 bytes -= copy;
317 while (unlikely(!left && bytes)) {
318 iov++;
319 buf = iov->iov_base;
320 copy = min(bytes, iov->iov_len);
321 left = copyin(to, buf, copy);
322 copy -= left;
323 skip = copy;
324 to += copy;
325 bytes -= copy;
326 }
327 kunmap(page);
328
329 done:
330 if (skip == iov->iov_len) {
331 iov++;
332 skip = 0;
333 }
334 i->count -= wanted - bytes;
335 i->nr_segs -= iov - i->iov;
336 i->iov = iov;
337 i->iov_offset = skip;
338 return wanted - bytes;
339 }
340
341 #ifdef PIPE_PARANOIA
342 static bool sanity(const struct iov_iter *i)
343 {
344 struct pipe_inode_info *pipe = i->pipe;
345 unsigned int p_head = pipe->head;
346 unsigned int p_tail = pipe->tail;
347 unsigned int p_mask = pipe->ring_size - 1;
348 unsigned int p_occupancy = pipe_occupancy(p_head, p_tail);
349 unsigned int i_head = i->head;
350 unsigned int idx;
351
352 if (i->iov_offset) {
353 struct pipe_buffer *p;
354 if (unlikely(p_occupancy == 0))
355 goto Bad; // pipe must be non-empty
356 if (unlikely(i_head != p_head - 1))
357 goto Bad; // must be at the last buffer...
358
359 p = &pipe->bufs[i_head & p_mask];
360 if (unlikely(p->offset + p->len != i->iov_offset))
361 goto Bad; // ... at the end of segment
362 } else {
363 if (i_head != p_head)
364 goto Bad; // must be right after the last buffer
365 }
366 return true;
367 Bad:
368 printk(KERN_ERR "idx = %d, offset = %zd\n", i_head, i->iov_offset);
369 printk(KERN_ERR "head = %d, tail = %d, buffers = %d\n",
370 p_head, p_tail, pipe->ring_size);
371 for (idx = 0; idx < pipe->ring_size; idx++)
372 printk(KERN_ERR "[%p %p %d %d]\n",
373 pipe->bufs[idx].ops,
374 pipe->bufs[idx].page,
375 pipe->bufs[idx].offset,
376 pipe->bufs[idx].len);
377 WARN_ON(1);
378 return false;
379 }
380 #else
381 #define sanity(i) true
382 #endif
383
384 static size_t copy_page_to_iter_pipe(struct page *page, size_t offset, size_t bytes,
385 struct iov_iter *i)
386 {
387 struct pipe_inode_info *pipe = i->pipe;
388 struct pipe_buffer *buf;
389 unsigned int p_tail = pipe->tail;
390 unsigned int p_mask = pipe->ring_size - 1;
391 unsigned int i_head = i->head;
392 size_t off;
393
394 if (unlikely(bytes > i->count))
395 bytes = i->count;
396
397 if (unlikely(!bytes))
398 return 0;
399
400 if (!sanity(i))
401 return 0;
402
403 off = i->iov_offset;
404 buf = &pipe->bufs[i_head & p_mask];
405 if (off) {
406 if (offset == off && buf->page == page) {
407 /* merge with the last one */
408 buf->len += bytes;
409 i->iov_offset += bytes;
410 goto out;
411 }
412 i_head++;
413 buf = &pipe->bufs[i_head & p_mask];
414 }
415 if (pipe_full(i_head, p_tail, pipe->max_usage))
416 return 0;
417
418 buf->ops = &page_cache_pipe_buf_ops;
419 get_page(page);
420 buf->page = page;
421 buf->offset = offset;
422 buf->len = bytes;
423
424 pipe->head = i_head + 1;
425 i->iov_offset = offset + bytes;
426 i->head = i_head;
427 out:
428 i->count -= bytes;
429 return bytes;
430 }
431
432 /*
433 * Fault in one or more iovecs of the given iov_iter, to a maximum length of
434 * bytes. For each iovec, fault in each page that constitutes the iovec.
435 *
436 * Return 0 on success, or non-zero if the memory could not be accessed (i.e.
437 * because it is an invalid address).
438 */
439 int iov_iter_fault_in_readable(const struct iov_iter *i, size_t bytes)
440 {
441 if (iter_is_iovec(i)) {
442 const struct iovec *p;
443 size_t skip;
444
445 if (bytes > i->count)
446 bytes = i->count;
447 for (p = i->iov, skip = i->iov_offset; bytes; p++, skip = 0) {
448 size_t len = min(bytes, p->iov_len - skip);
449 int err;
450
451 if (unlikely(!len))
452 continue;
453 err = fault_in_pages_readable(p->iov_base + skip, len);
454 if (unlikely(err))
455 return err;
456 bytes -= len;
457 }
458 }
459 return 0;
460 }
461 EXPORT_SYMBOL(iov_iter_fault_in_readable);
462
463 void iov_iter_init(struct iov_iter *i, unsigned int direction,
464 const struct iovec *iov, unsigned long nr_segs,
465 size_t count)
466 {
467 WARN_ON(direction & ~(READ | WRITE));
468 *i = (struct iov_iter) {
469 .iter_type = ITER_IOVEC,
470 .data_source = direction,
471 .iov = iov,
472 .nr_segs = nr_segs,
473 .iov_offset = 0,
474 .count = count
475 };
476 }
477 EXPORT_SYMBOL(iov_iter_init);
478
479 static inline bool allocated(struct pipe_buffer *buf)
480 {
481 return buf->ops == &default_pipe_buf_ops;
482 }
483
484 static inline void data_start(const struct iov_iter *i,
485 unsigned int *iter_headp, size_t *offp)
486 {
487 unsigned int p_mask = i->pipe->ring_size - 1;
488 unsigned int iter_head = i->head;
489 size_t off = i->iov_offset;
490
491 if (off && (!allocated(&i->pipe->bufs[iter_head & p_mask]) ||
492 off == PAGE_SIZE)) {
493 iter_head++;
494 off = 0;
495 }
496 *iter_headp = iter_head;
497 *offp = off;
498 }
499
500 static size_t push_pipe(struct iov_iter *i, size_t size,
501 int *iter_headp, size_t *offp)
502 {
503 struct pipe_inode_info *pipe = i->pipe;
504 unsigned int p_tail = pipe->tail;
505 unsigned int p_mask = pipe->ring_size - 1;
506 unsigned int iter_head;
507 size_t off;
508 ssize_t left;
509
510 if (unlikely(size > i->count))
511 size = i->count;
512 if (unlikely(!size))
513 return 0;
514
515 left = size;
516 data_start(i, &iter_head, &off);
517 *iter_headp = iter_head;
518 *offp = off;
519 if (off) {
520 left -= PAGE_SIZE - off;
521 if (left <= 0) {
522 pipe->bufs[iter_head & p_mask].len += size;
523 return size;
524 }
525 pipe->bufs[iter_head & p_mask].len = PAGE_SIZE;
526 iter_head++;
527 }
528 while (!pipe_full(iter_head, p_tail, pipe->max_usage)) {
529 struct pipe_buffer *buf = &pipe->bufs[iter_head & p_mask];
530 struct page *page = alloc_page(GFP_USER);
531 if (!page)
532 break;
533
534 buf->ops = &default_pipe_buf_ops;
535 buf->page = page;
536 buf->offset = 0;
537 buf->len = min_t(ssize_t, left, PAGE_SIZE);
538 left -= buf->len;
539 iter_head++;
540 pipe->head = iter_head;
541
542 if (left == 0)
543 return size;
544 }
545 return size - left;
546 }
547
548 static size_t copy_pipe_to_iter(const void *addr, size_t bytes,
549 struct iov_iter *i)
550 {
551 struct pipe_inode_info *pipe = i->pipe;
552 unsigned int p_mask = pipe->ring_size - 1;
553 unsigned int i_head;
554 size_t n, off;
555
556 if (!sanity(i))
557 return 0;
558
559 bytes = n = push_pipe(i, bytes, &i_head, &off);
560 if (unlikely(!n))
561 return 0;
562 do {
563 size_t chunk = min_t(size_t, n, PAGE_SIZE - off);
564 memcpy_to_page(pipe->bufs[i_head & p_mask].page, off, addr, chunk);
565 i->head = i_head;
566 i->iov_offset = off + chunk;
567 n -= chunk;
568 addr += chunk;
569 off = 0;
570 i_head++;
571 } while (n);
572 i->count -= bytes;
573 return bytes;
574 }
575
576 static __wsum csum_and_memcpy(void *to, const void *from, size_t len,
577 __wsum sum, size_t off)
578 {
579 __wsum next = csum_partial_copy_nocheck(from, to, len);
580 return csum_block_add(sum, next, off);
581 }
582
583 static size_t csum_and_copy_to_pipe_iter(const void *addr, size_t bytes,
584 struct iov_iter *i, __wsum *sump)
585 {
586 struct pipe_inode_info *pipe = i->pipe;
587 unsigned int p_mask = pipe->ring_size - 1;
588 __wsum sum = *sump;
589 size_t off = 0;
590 unsigned int i_head;
591 size_t r;
592
593 if (!sanity(i))
594 return 0;
595
596 bytes = push_pipe(i, bytes, &i_head, &r);
597 while (bytes) {
598 size_t chunk = min_t(size_t, bytes, PAGE_SIZE - r);
599 char *p = kmap_local_page(pipe->bufs[i_head & p_mask].page);
600 sum = csum_and_memcpy(p + r, addr + off, chunk, sum, off);
601 kunmap_local(p);
602 i->head = i_head;
603 i->iov_offset = r + chunk;
604 bytes -= chunk;
605 off += chunk;
606 r = 0;
607 i_head++;
608 }
609 *sump = sum;
610 i->count -= off;
611 return off;
612 }
613
614 size_t _copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
615 {
616 if (unlikely(iov_iter_is_pipe(i)))
617 return copy_pipe_to_iter(addr, bytes, i);
618 if (iter_is_iovec(i))
619 might_fault();
620 iterate_and_advance(i, bytes, base, len, off,
621 copyout(base, addr + off, len),
622 memcpy(base, addr + off, len)
623 )
624
625 return bytes;
626 }
627 EXPORT_SYMBOL(_copy_to_iter);
628
629 #ifdef CONFIG_ARCH_HAS_COPY_MC
630 static int copyout_mc(void __user *to, const void *from, size_t n)
631 {
632 if (access_ok(to, n)) {
633 instrument_copy_to_user(to, from, n);
634 n = copy_mc_to_user((__force void *) to, from, n);
635 }
636 return n;
637 }
638
639 static size_t copy_mc_pipe_to_iter(const void *addr, size_t bytes,
640 struct iov_iter *i)
641 {
642 struct pipe_inode_info *pipe = i->pipe;
643 unsigned int p_mask = pipe->ring_size - 1;
644 unsigned int i_head;
645 size_t n, off, xfer = 0;
646
647 if (!sanity(i))
648 return 0;
649
650 n = push_pipe(i, bytes, &i_head, &off);
651 while (n) {
652 size_t chunk = min_t(size_t, n, PAGE_SIZE - off);
653 char *p = kmap_local_page(pipe->bufs[i_head & p_mask].page);
654 unsigned long rem;
655 rem = copy_mc_to_kernel(p + off, addr + xfer, chunk);
656 chunk -= rem;
657 kunmap_local(p);
658 i->head = i_head;
659 i->iov_offset = off + chunk;
660 xfer += chunk;
661 if (rem)
662 break;
663 n -= chunk;
664 off = 0;
665 i_head++;
666 }
667 i->count -= xfer;
668 return xfer;
669 }
670
671 /**
672 * _copy_mc_to_iter - copy to iter with source memory error exception handling
673 * @addr: source kernel address
674 * @bytes: total transfer length
675 * @iter: destination iterator
676 *
677 * The pmem driver deploys this for the dax operation
678 * (dax_copy_to_iter()) for dax reads (bypass page-cache and the
679 * block-layer). Upon #MC read(2) aborts and returns EIO or the bytes
680 * successfully copied.
681 *
682 * The main differences between this and typical _copy_to_iter().
683 *
684 * * Typical tail/residue handling after a fault retries the copy
685 * byte-by-byte until the fault happens again. Re-triggering machine
686 * checks is potentially fatal so the implementation uses source
687 * alignment and poison alignment assumptions to avoid re-triggering
688 * hardware exceptions.
689 *
690 * * ITER_KVEC, ITER_PIPE, and ITER_BVEC can return short copies.
691 * Compare to copy_to_iter() where only ITER_IOVEC attempts might return
692 * a short copy.
693 */
694 size_t _copy_mc_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
695 {
696 if (unlikely(iov_iter_is_pipe(i)))
697 return copy_mc_pipe_to_iter(addr, bytes, i);
698 if (iter_is_iovec(i))
699 might_fault();
700 __iterate_and_advance(i, bytes, base, len, off,
701 copyout_mc(base, addr + off, len),
702 copy_mc_to_kernel(base, addr + off, len)
703 )
704
705 return bytes;
706 }
707 EXPORT_SYMBOL_GPL(_copy_mc_to_iter);
708 #endif /* CONFIG_ARCH_HAS_COPY_MC */
709
710 size_t _copy_from_iter(void *addr, size_t bytes, struct iov_iter *i)
711 {
712 if (unlikely(iov_iter_is_pipe(i))) {
713 WARN_ON(1);
714 return 0;
715 }
716 if (iter_is_iovec(i))
717 might_fault();
718 iterate_and_advance(i, bytes, base, len, off,
719 copyin(addr + off, base, len),
720 memcpy(addr + off, base, len)
721 )
722
723 return bytes;
724 }
725 EXPORT_SYMBOL(_copy_from_iter);
726
727 size_t _copy_from_iter_nocache(void *addr, size_t bytes, struct iov_iter *i)
728 {
729 if (unlikely(iov_iter_is_pipe(i))) {
730 WARN_ON(1);
731 return 0;
732 }
733 iterate_and_advance(i, bytes, base, len, off,
734 __copy_from_user_inatomic_nocache(addr + off, base, len),
735 memcpy(addr + off, base, len)
736 )
737
738 return bytes;
739 }
740 EXPORT_SYMBOL(_copy_from_iter_nocache);
741
742 #ifdef CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE
743 /**
744 * _copy_from_iter_flushcache - write destination through cpu cache
745 * @addr: destination kernel address
746 * @bytes: total transfer length
747 * @iter: source iterator
748 *
749 * The pmem driver arranges for filesystem-dax to use this facility via
750 * dax_copy_from_iter() for ensuring that writes to persistent memory
751 * are flushed through the CPU cache. It is differentiated from
752 * _copy_from_iter_nocache() in that guarantees all data is flushed for
753 * all iterator types. The _copy_from_iter_nocache() only attempts to
754 * bypass the cache for the ITER_IOVEC case, and on some archs may use
755 * instructions that strand dirty-data in the cache.
756 */
757 size_t _copy_from_iter_flushcache(void *addr, size_t bytes, struct iov_iter *i)
758 {
759 if (unlikely(iov_iter_is_pipe(i))) {
760 WARN_ON(1);
761 return 0;
762 }
763 iterate_and_advance(i, bytes, base, len, off,
764 __copy_from_user_flushcache(addr + off, base, len),
765 memcpy_flushcache(addr + off, base, len)
766 )
767
768 return bytes;
769 }
770 EXPORT_SYMBOL_GPL(_copy_from_iter_flushcache);
771 #endif
772
773 static inline bool page_copy_sane(struct page *page, size_t offset, size_t n)
774 {
775 struct page *head;
776 size_t v = n + offset;
777
778 /*
779 * The general case needs to access the page order in order
780 * to compute the page size.
781 * However, we mostly deal with order-0 pages and thus can
782 * avoid a possible cache line miss for requests that fit all
783 * page orders.
784 */
785 if (n <= v && v <= PAGE_SIZE)
786 return true;
787
788 head = compound_head(page);
789 v += (page - head) << PAGE_SHIFT;
790
791 if (likely(n <= v && v <= (page_size(head))))
792 return true;
793 WARN_ON(1);
794 return false;
795 }
796
797 static size_t __copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
798 struct iov_iter *i)
799 {
800 if (likely(iter_is_iovec(i)))
801 return copy_page_to_iter_iovec(page, offset, bytes, i);
802 if (iov_iter_is_bvec(i) || iov_iter_is_kvec(i) || iov_iter_is_xarray(i)) {
803 void *kaddr = kmap_local_page(page);
804 size_t wanted = _copy_to_iter(kaddr + offset, bytes, i);
805 kunmap_local(kaddr);
806 return wanted;
807 }
808 if (iov_iter_is_pipe(i))
809 return copy_page_to_iter_pipe(page, offset, bytes, i);
810 if (unlikely(iov_iter_is_discard(i))) {
811 if (unlikely(i->count < bytes))
812 bytes = i->count;
813 i->count -= bytes;
814 return bytes;
815 }
816 WARN_ON(1);
817 return 0;
818 }
819
820 size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
821 struct iov_iter *i)
822 {
823 size_t res = 0;
824 if (unlikely(!page_copy_sane(page, offset, bytes)))
825 return 0;
826 page += offset / PAGE_SIZE; // first subpage
827 offset %= PAGE_SIZE;
828 while (1) {
829 size_t n = __copy_page_to_iter(page, offset,
830 min(bytes, (size_t)PAGE_SIZE - offset), i);
831 res += n;
832 bytes -= n;
833 if (!bytes || !n)
834 break;
835 offset += n;
836 if (offset == PAGE_SIZE) {
837 page++;
838 offset = 0;
839 }
840 }
841 return res;
842 }
843 EXPORT_SYMBOL(copy_page_to_iter);
844
845 size_t copy_page_from_iter(struct page *page, size_t offset, size_t bytes,
846 struct iov_iter *i)
847 {
848 if (unlikely(!page_copy_sane(page, offset, bytes)))
849 return 0;
850 if (likely(iter_is_iovec(i)))
851 return copy_page_from_iter_iovec(page, offset, bytes, i);
852 if (iov_iter_is_bvec(i) || iov_iter_is_kvec(i) || iov_iter_is_xarray(i)) {
853 void *kaddr = kmap_local_page(page);
854 size_t wanted = _copy_from_iter(kaddr + offset, bytes, i);
855 kunmap_local(kaddr);
856 return wanted;
857 }
858 WARN_ON(1);
859 return 0;
860 }
861 EXPORT_SYMBOL(copy_page_from_iter);
862
863 static size_t pipe_zero(size_t bytes, struct iov_iter *i)
864 {
865 struct pipe_inode_info *pipe = i->pipe;
866 unsigned int p_mask = pipe->ring_size - 1;
867 unsigned int i_head;
868 size_t n, off;
869
870 if (!sanity(i))
871 return 0;
872
873 bytes = n = push_pipe(i, bytes, &i_head, &off);
874 if (unlikely(!n))
875 return 0;
876
877 do {
878 size_t chunk = min_t(size_t, n, PAGE_SIZE - off);
879 char *p = kmap_local_page(pipe->bufs[i_head & p_mask].page);
880 memset(p + off, 0, chunk);
881 kunmap_local(p);
882 i->head = i_head;
883 i->iov_offset = off + chunk;
884 n -= chunk;
885 off = 0;
886 i_head++;
887 } while (n);
888 i->count -= bytes;
889 return bytes;
890 }
891
892 size_t iov_iter_zero(size_t bytes, struct iov_iter *i)
893 {
894 if (unlikely(iov_iter_is_pipe(i)))
895 return pipe_zero(bytes, i);
896 iterate_and_advance(i, bytes, base, len, count,
897 clear_user(base, len),
898 memset(base, 0, len)
899 )
900
901 return bytes;
902 }
903 EXPORT_SYMBOL(iov_iter_zero);
904
905 size_t copy_page_from_iter_atomic(struct page *page, unsigned offset, size_t bytes,
906 struct iov_iter *i)
907 {
908 char *kaddr = kmap_atomic(page), *p = kaddr + offset;
909 if (unlikely(!page_copy_sane(page, offset, bytes))) {
910 kunmap_atomic(kaddr);
911 return 0;
912 }
913 if (unlikely(iov_iter_is_pipe(i) || iov_iter_is_discard(i))) {
914 kunmap_atomic(kaddr);
915 WARN_ON(1);
916 return 0;
917 }
918 iterate_and_advance(i, bytes, base, len, off,
919 copyin(p + off, base, len),
920 memcpy(p + off, base, len)
921 )
922 kunmap_atomic(kaddr);
923 return bytes;
924 }
925 EXPORT_SYMBOL(copy_page_from_iter_atomic);
926
927 static inline void pipe_truncate(struct iov_iter *i)
928 {
929 struct pipe_inode_info *pipe = i->pipe;
930 unsigned int p_tail = pipe->tail;
931 unsigned int p_head = pipe->head;
932 unsigned int p_mask = pipe->ring_size - 1;
933
934 if (!pipe_empty(p_head, p_tail)) {
935 struct pipe_buffer *buf;
936 unsigned int i_head = i->head;
937 size_t off = i->iov_offset;
938
939 if (off) {
940 buf = &pipe->bufs[i_head & p_mask];
941 buf->len = off - buf->offset;
942 i_head++;
943 }
944 while (p_head != i_head) {
945 p_head--;
946 pipe_buf_release(pipe, &pipe->bufs[p_head & p_mask]);
947 }
948
949 pipe->head = p_head;
950 }
951 }
952
953 static void pipe_advance(struct iov_iter *i, size_t size)
954 {
955 struct pipe_inode_info *pipe = i->pipe;
956 if (size) {
957 struct pipe_buffer *buf;
958 unsigned int p_mask = pipe->ring_size - 1;
959 unsigned int i_head = i->head;
960 size_t off = i->iov_offset, left = size;
961
962 if (off) /* make it relative to the beginning of buffer */
963 left += off - pipe->bufs[i_head & p_mask].offset;
964 while (1) {
965 buf = &pipe->bufs[i_head & p_mask];
966 if (left <= buf->len)
967 break;
968 left -= buf->len;
969 i_head++;
970 }
971 i->head = i_head;
972 i->iov_offset = buf->offset + left;
973 }
974 i->count -= size;
975 /* ... and discard everything past that point */
976 pipe_truncate(i);
977 }
978
979 static void iov_iter_bvec_advance(struct iov_iter *i, size_t size)
980 {
981 struct bvec_iter bi;
982
983 bi.bi_size = i->count;
984 bi.bi_bvec_done = i->iov_offset;
985 bi.bi_idx = 0;
986 bvec_iter_advance(i->bvec, &bi, size);
987
988 i->bvec += bi.bi_idx;
989 i->nr_segs -= bi.bi_idx;
990 i->count = bi.bi_size;
991 i->iov_offset = bi.bi_bvec_done;
992 }
993
994 static void iov_iter_iovec_advance(struct iov_iter *i, size_t size)
995 {
996 const struct iovec *iov, *end;
997
998 if (!i->count)
999 return;
1000 i->count -= size;
1001
1002 size += i->iov_offset; // from beginning of current segment
1003 for (iov = i->iov, end = iov + i->nr_segs; iov < end; iov++) {
1004 if (likely(size < iov->iov_len))
1005 break;
1006 size -= iov->iov_len;
1007 }
1008 i->iov_offset = size;
1009 i->nr_segs -= iov - i->iov;
1010 i->iov = iov;
1011 }
1012
1013 void iov_iter_advance(struct iov_iter *i, size_t size)
1014 {
1015 if (unlikely(i->count < size))
1016 size = i->count;
1017 if (likely(iter_is_iovec(i) || iov_iter_is_kvec(i))) {
1018 /* iovec and kvec have identical layouts */
1019 iov_iter_iovec_advance(i, size);
1020 } else if (iov_iter_is_bvec(i)) {
1021 iov_iter_bvec_advance(i, size);
1022 } else if (iov_iter_is_pipe(i)) {
1023 pipe_advance(i, size);
1024 } else if (unlikely(iov_iter_is_xarray(i))) {
1025 i->iov_offset += size;
1026 i->count -= size;
1027 } else if (iov_iter_is_discard(i)) {
1028 i->count -= size;
1029 }
1030 }
1031 EXPORT_SYMBOL(iov_iter_advance);
1032
1033 void iov_iter_revert(struct iov_iter *i, size_t unroll)
1034 {
1035 if (!unroll)
1036 return;
1037 if (WARN_ON(unroll > MAX_RW_COUNT))
1038 return;
1039 i->count += unroll;
1040 if (unlikely(iov_iter_is_pipe(i))) {
1041 struct pipe_inode_info *pipe = i->pipe;
1042 unsigned int p_mask = pipe->ring_size - 1;
1043 unsigned int i_head = i->head;
1044 size_t off = i->iov_offset;
1045 while (1) {
1046 struct pipe_buffer *b = &pipe->bufs[i_head & p_mask];
1047 size_t n = off - b->offset;
1048 if (unroll < n) {
1049 off -= unroll;
1050 break;
1051 }
1052 unroll -= n;
1053 if (!unroll && i_head == i->start_head) {
1054 off = 0;
1055 break;
1056 }
1057 i_head--;
1058 b = &pipe->bufs[i_head & p_mask];
1059 off = b->offset + b->len;
1060 }
1061 i->iov_offset = off;
1062 i->head = i_head;
1063 pipe_truncate(i);
1064 return;
1065 }
1066 if (unlikely(iov_iter_is_discard(i)))
1067 return;
1068 if (unroll <= i->iov_offset) {
1069 i->iov_offset -= unroll;
1070 return;
1071 }
1072 unroll -= i->iov_offset;
1073 if (iov_iter_is_xarray(i)) {
1074 BUG(); /* We should never go beyond the start of the specified
1075 * range since we might then be straying into pages that
1076 * aren't pinned.
1077 */
1078 } else if (iov_iter_is_bvec(i)) {
1079 const struct bio_vec *bvec = i->bvec;
1080 while (1) {
1081 size_t n = (--bvec)->bv_len;
1082 i->nr_segs++;
1083 if (unroll <= n) {
1084 i->bvec = bvec;
1085 i->iov_offset = n - unroll;
1086 return;
1087 }
1088 unroll -= n;
1089 }
1090 } else { /* same logics for iovec and kvec */
1091 const struct iovec *iov = i->iov;
1092 while (1) {
1093 size_t n = (--iov)->iov_len;
1094 i->nr_segs++;
1095 if (unroll <= n) {
1096 i->iov = iov;
1097 i->iov_offset = n - unroll;
1098 return;
1099 }
1100 unroll -= n;
1101 }
1102 }
1103 }
1104 EXPORT_SYMBOL(iov_iter_revert);
1105
1106 /*
1107 * Return the count of just the current iov_iter segment.
1108 */
1109 size_t iov_iter_single_seg_count(const struct iov_iter *i)
1110 {
1111 if (i->nr_segs > 1) {
1112 if (likely(iter_is_iovec(i) || iov_iter_is_kvec(i)))
1113 return min(i->count, i->iov->iov_len - i->iov_offset);
1114 if (iov_iter_is_bvec(i))
1115 return min(i->count, i->bvec->bv_len - i->iov_offset);
1116 }
1117 return i->count;
1118 }
1119 EXPORT_SYMBOL(iov_iter_single_seg_count);
1120
1121 void iov_iter_kvec(struct iov_iter *i, unsigned int direction,
1122 const struct kvec *kvec, unsigned long nr_segs,
1123 size_t count)
1124 {
1125 WARN_ON(direction & ~(READ | WRITE));
1126 *i = (struct iov_iter){
1127 .iter_type = ITER_KVEC,
1128 .data_source = direction,
1129 .kvec = kvec,
1130 .nr_segs = nr_segs,
1131 .iov_offset = 0,
1132 .count = count
1133 };
1134 }
1135 EXPORT_SYMBOL(iov_iter_kvec);
1136
1137 void iov_iter_bvec(struct iov_iter *i, unsigned int direction,
1138 const struct bio_vec *bvec, unsigned long nr_segs,
1139 size_t count)
1140 {
1141 WARN_ON(direction & ~(READ | WRITE));
1142 *i = (struct iov_iter){
1143 .iter_type = ITER_BVEC,
1144 .data_source = direction,
1145 .bvec = bvec,
1146 .nr_segs = nr_segs,
1147 .iov_offset = 0,
1148 .count = count
1149 };
1150 }
1151 EXPORT_SYMBOL(iov_iter_bvec);
1152
1153 void iov_iter_pipe(struct iov_iter *i, unsigned int direction,
1154 struct pipe_inode_info *pipe,
1155 size_t count)
1156 {
1157 BUG_ON(direction != READ);
1158 WARN_ON(pipe_full(pipe->head, pipe->tail, pipe->ring_size));
1159 *i = (struct iov_iter){
1160 .iter_type = ITER_PIPE,
1161 .data_source = false,
1162 .pipe = pipe,
1163 .head = pipe->head,
1164 .start_head = pipe->head,
1165 .iov_offset = 0,
1166 .count = count
1167 };
1168 }
1169 EXPORT_SYMBOL(iov_iter_pipe);
1170
1171 /**
1172 * iov_iter_xarray - Initialise an I/O iterator to use the pages in an xarray
1173 * @i: The iterator to initialise.
1174 * @direction: The direction of the transfer.
1175 * @xarray: The xarray to access.
1176 * @start: The start file position.
1177 * @count: The size of the I/O buffer in bytes.
1178 *
1179 * Set up an I/O iterator to either draw data out of the pages attached to an
1180 * inode or to inject data into those pages. The pages *must* be prevented
1181 * from evaporation, either by taking a ref on them or locking them by the
1182 * caller.
1183 */
1184 void iov_iter_xarray(struct iov_iter *i, unsigned int direction,
1185 struct xarray *xarray, loff_t start, size_t count)
1186 {
1187 BUG_ON(direction & ~1);
1188 *i = (struct iov_iter) {
1189 .iter_type = ITER_XARRAY,
1190 .data_source = direction,
1191 .xarray = xarray,
1192 .xarray_start = start,
1193 .count = count,
1194 .iov_offset = 0
1195 };
1196 }
1197 EXPORT_SYMBOL(iov_iter_xarray);
1198
1199 /**
1200 * iov_iter_discard - Initialise an I/O iterator that discards data
1201 * @i: The iterator to initialise.
1202 * @direction: The direction of the transfer.
1203 * @count: The size of the I/O buffer in bytes.
1204 *
1205 * Set up an I/O iterator that just discards everything that's written to it.
1206 * It's only available as a READ iterator.
1207 */
1208 void iov_iter_discard(struct iov_iter *i, unsigned int direction, size_t count)
1209 {
1210 BUG_ON(direction != READ);
1211 *i = (struct iov_iter){
1212 .iter_type = ITER_DISCARD,
1213 .data_source = false,
1214 .count = count,
1215 .iov_offset = 0
1216 };
1217 }
1218 EXPORT_SYMBOL(iov_iter_discard);
1219
1220 static unsigned long iov_iter_alignment_iovec(const struct iov_iter *i)
1221 {
1222 unsigned long res = 0;
1223 size_t size = i->count;
1224 size_t skip = i->iov_offset;
1225 unsigned k;
1226
1227 for (k = 0; k < i->nr_segs; k++, skip = 0) {
1228 size_t len = i->iov[k].iov_len - skip;
1229 if (len) {
1230 res |= (unsigned long)i->iov[k].iov_base + skip;
1231 if (len > size)
1232 len = size;
1233 res |= len;
1234 size -= len;
1235 if (!size)
1236 break;
1237 }
1238 }
1239 return res;
1240 }
1241
1242 static unsigned long iov_iter_alignment_bvec(const struct iov_iter *i)
1243 {
1244 unsigned res = 0;
1245 size_t size = i->count;
1246 unsigned skip = i->iov_offset;
1247 unsigned k;
1248
1249 for (k = 0; k < i->nr_segs; k++, skip = 0) {
1250 size_t len = i->bvec[k].bv_len - skip;
1251 res |= (unsigned long)i->bvec[k].bv_offset + skip;
1252 if (len > size)
1253 len = size;
1254 res |= len;
1255 size -= len;
1256 if (!size)
1257 break;
1258 }
1259 return res;
1260 }
1261
1262 unsigned long iov_iter_alignment(const struct iov_iter *i)
1263 {
1264 /* iovec and kvec have identical layouts */
1265 if (likely(iter_is_iovec(i) || iov_iter_is_kvec(i)))
1266 return iov_iter_alignment_iovec(i);
1267
1268 if (iov_iter_is_bvec(i))
1269 return iov_iter_alignment_bvec(i);
1270
1271 if (iov_iter_is_pipe(i)) {
1272 unsigned int p_mask = i->pipe->ring_size - 1;
1273 size_t size = i->count;
1274
1275 if (size && i->iov_offset && allocated(&i->pipe->bufs[i->head & p_mask]))
1276 return size | i->iov_offset;
1277 return size;
1278 }
1279
1280 if (iov_iter_is_xarray(i))
1281 return (i->xarray_start + i->iov_offset) | i->count;
1282
1283 return 0;
1284 }
1285 EXPORT_SYMBOL(iov_iter_alignment);
1286
1287 unsigned long iov_iter_gap_alignment(const struct iov_iter *i)
1288 {
1289 unsigned long res = 0;
1290 unsigned long v = 0;
1291 size_t size = i->count;
1292 unsigned k;
1293
1294 if (WARN_ON(!iter_is_iovec(i)))
1295 return ~0U;
1296
1297 for (k = 0; k < i->nr_segs; k++) {
1298 if (i->iov[k].iov_len) {
1299 unsigned long base = (unsigned long)i->iov[k].iov_base;
1300 if (v) // if not the first one
1301 res |= base | v; // this start | previous end
1302 v = base + i->iov[k].iov_len;
1303 if (size <= i->iov[k].iov_len)
1304 break;
1305 size -= i->iov[k].iov_len;
1306 }
1307 }
1308 return res;
1309 }
1310 EXPORT_SYMBOL(iov_iter_gap_alignment);
1311
1312 static inline ssize_t __pipe_get_pages(struct iov_iter *i,
1313 size_t maxsize,
1314 struct page **pages,
1315 int iter_head,
1316 size_t *start)
1317 {
1318 struct pipe_inode_info *pipe = i->pipe;
1319 unsigned int p_mask = pipe->ring_size - 1;
1320 ssize_t n = push_pipe(i, maxsize, &iter_head, start);
1321 if (!n)
1322 return -EFAULT;
1323
1324 maxsize = n;
1325 n += *start;
1326 while (n > 0) {
1327 get_page(*pages++ = pipe->bufs[iter_head & p_mask].page);
1328 iter_head++;
1329 n -= PAGE_SIZE;
1330 }
1331
1332 return maxsize;
1333 }
1334
1335 static ssize_t pipe_get_pages(struct iov_iter *i,
1336 struct page **pages, size_t maxsize, unsigned maxpages,
1337 size_t *start)
1338 {
1339 unsigned int iter_head, npages;
1340 size_t capacity;
1341
1342 if (!sanity(i))
1343 return -EFAULT;
1344
1345 data_start(i, &iter_head, start);
1346 /* Amount of free space: some of this one + all after this one */
1347 npages = pipe_space_for_user(iter_head, i->pipe->tail, i->pipe);
1348 capacity = min(npages, maxpages) * PAGE_SIZE - *start;
1349
1350 return __pipe_get_pages(i, min(maxsize, capacity), pages, iter_head, start);
1351 }
1352
1353 static ssize_t iter_xarray_populate_pages(struct page **pages, struct xarray *xa,
1354 pgoff_t index, unsigned int nr_pages)
1355 {
1356 XA_STATE(xas, xa, index);
1357 struct page *page;
1358 unsigned int ret = 0;
1359
1360 rcu_read_lock();
1361 for (page = xas_load(&xas); page; page = xas_next(&xas)) {
1362 if (xas_retry(&xas, page))
1363 continue;
1364
1365 /* Has the page moved or been split? */
1366 if (unlikely(page != xas_reload(&xas))) {
1367 xas_reset(&xas);
1368 continue;
1369 }
1370
1371 pages[ret] = find_subpage(page, xas.xa_index);
1372 get_page(pages[ret]);
1373 if (++ret == nr_pages)
1374 break;
1375 }
1376 rcu_read_unlock();
1377 return ret;
1378 }
1379
1380 static ssize_t iter_xarray_get_pages(struct iov_iter *i,
1381 struct page **pages, size_t maxsize,
1382 unsigned maxpages, size_t *_start_offset)
1383 {
1384 unsigned nr, offset;
1385 pgoff_t index, count;
1386 size_t size = maxsize, actual;
1387 loff_t pos;
1388
1389 if (!size || !maxpages)
1390 return 0;
1391
1392 pos = i->xarray_start + i->iov_offset;
1393 index = pos >> PAGE_SHIFT;
1394 offset = pos & ~PAGE_MASK;
1395 *_start_offset = offset;
1396
1397 count = 1;
1398 if (size > PAGE_SIZE - offset) {
1399 size -= PAGE_SIZE - offset;
1400 count += size >> PAGE_SHIFT;
1401 size &= ~PAGE_MASK;
1402 if (size)
1403 count++;
1404 }
1405
1406 if (count > maxpages)
1407 count = maxpages;
1408
1409 nr = iter_xarray_populate_pages(pages, i->xarray, index, count);
1410 if (nr == 0)
1411 return 0;
1412
1413 actual = PAGE_SIZE * nr;
1414 actual -= offset;
1415 if (nr == count && size > 0) {
1416 unsigned last_offset = (nr > 1) ? 0 : offset;
1417 actual -= PAGE_SIZE - (last_offset + size);
1418 }
1419 return actual;
1420 }
1421
1422 /* must be done on non-empty ITER_IOVEC one */
1423 static unsigned long first_iovec_segment(const struct iov_iter *i,
1424 size_t *size, size_t *start,
1425 size_t maxsize, unsigned maxpages)
1426 {
1427 size_t skip;
1428 long k;
1429
1430 for (k = 0, skip = i->iov_offset; k < i->nr_segs; k++, skip = 0) {
1431 unsigned long addr = (unsigned long)i->iov[k].iov_base + skip;
1432 size_t len = i->iov[k].iov_len - skip;
1433
1434 if (unlikely(!len))
1435 continue;
1436 if (len > maxsize)
1437 len = maxsize;
1438 len += (*start = addr % PAGE_SIZE);
1439 if (len > maxpages * PAGE_SIZE)
1440 len = maxpages * PAGE_SIZE;
1441 *size = len;
1442 return addr & PAGE_MASK;
1443 }
1444 BUG(); // if it had been empty, we wouldn't get called
1445 }
1446
1447 /* must be done on non-empty ITER_BVEC one */
1448 static struct page *first_bvec_segment(const struct iov_iter *i,
1449 size_t *size, size_t *start,
1450 size_t maxsize, unsigned maxpages)
1451 {
1452 struct page *page;
1453 size_t skip = i->iov_offset, len;
1454
1455 len = i->bvec->bv_len - skip;
1456 if (len > maxsize)
1457 len = maxsize;
1458 skip += i->bvec->bv_offset;
1459 page = i->bvec->bv_page + skip / PAGE_SIZE;
1460 len += (*start = skip % PAGE_SIZE);
1461 if (len > maxpages * PAGE_SIZE)
1462 len = maxpages * PAGE_SIZE;
1463 *size = len;
1464 return page;
1465 }
1466
1467 ssize_t iov_iter_get_pages(struct iov_iter *i,
1468 struct page **pages, size_t maxsize, unsigned maxpages,
1469 size_t *start)
1470 {
1471 size_t len;
1472 int n, res;
1473
1474 if (maxsize > i->count)
1475 maxsize = i->count;
1476 if (!maxsize)
1477 return 0;
1478
1479 if (likely(iter_is_iovec(i))) {
1480 unsigned long addr;
1481
1482 addr = first_iovec_segment(i, &len, start, maxsize, maxpages);
1483 n = DIV_ROUND_UP(len, PAGE_SIZE);
1484 res = get_user_pages_fast(addr, n,
1485 iov_iter_rw(i) != WRITE ? FOLL_WRITE : 0,
1486 pages);
1487 if (unlikely(res < 0))
1488 return res;
1489 return (res == n ? len : res * PAGE_SIZE) - *start;
1490 }
1491 if (iov_iter_is_bvec(i)) {
1492 struct page *page;
1493
1494 page = first_bvec_segment(i, &len, start, maxsize, maxpages);
1495 n = DIV_ROUND_UP(len, PAGE_SIZE);
1496 while (n--)
1497 get_page(*pages++ = page++);
1498 return len - *start;
1499 }
1500 if (iov_iter_is_pipe(i))
1501 return pipe_get_pages(i, pages, maxsize, maxpages, start);
1502 if (iov_iter_is_xarray(i))
1503 return iter_xarray_get_pages(i, pages, maxsize, maxpages, start);
1504 return -EFAULT;
1505 }
1506 EXPORT_SYMBOL(iov_iter_get_pages);
1507
1508 static struct page **get_pages_array(size_t n)
1509 {
1510 return kvmalloc_array(n, sizeof(struct page *), GFP_KERNEL);
1511 }
1512
1513 static ssize_t pipe_get_pages_alloc(struct iov_iter *i,
1514 struct page ***pages, size_t maxsize,
1515 size_t *start)
1516 {
1517 struct page **p;
1518 unsigned int iter_head, npages;
1519 ssize_t n;
1520
1521 if (!sanity(i))
1522 return -EFAULT;
1523
1524 data_start(i, &iter_head, start);
1525 /* Amount of free space: some of this one + all after this one */
1526 npages = pipe_space_for_user(iter_head, i->pipe->tail, i->pipe);
1527 n = npages * PAGE_SIZE - *start;
1528 if (maxsize > n)
1529 maxsize = n;
1530 else
1531 npages = DIV_ROUND_UP(maxsize + *start, PAGE_SIZE);
1532 p = get_pages_array(npages);
1533 if (!p)
1534 return -ENOMEM;
1535 n = __pipe_get_pages(i, maxsize, p, iter_head, start);
1536 if (n > 0)
1537 *pages = p;
1538 else
1539 kvfree(p);
1540 return n;
1541 }
1542
1543 static ssize_t iter_xarray_get_pages_alloc(struct iov_iter *i,
1544 struct page ***pages, size_t maxsize,
1545 size_t *_start_offset)
1546 {
1547 struct page **p;
1548 unsigned nr, offset;
1549 pgoff_t index, count;
1550 size_t size = maxsize, actual;
1551 loff_t pos;
1552
1553 if (!size)
1554 return 0;
1555
1556 pos = i->xarray_start + i->iov_offset;
1557 index = pos >> PAGE_SHIFT;
1558 offset = pos & ~PAGE_MASK;
1559 *_start_offset = offset;
1560
1561 count = 1;
1562 if (size > PAGE_SIZE - offset) {
1563 size -= PAGE_SIZE - offset;
1564 count += size >> PAGE_SHIFT;
1565 size &= ~PAGE_MASK;
1566 if (size)
1567 count++;
1568 }
1569
1570 p = get_pages_array(count);
1571 if (!p)
1572 return -ENOMEM;
1573 *pages = p;
1574
1575 nr = iter_xarray_populate_pages(p, i->xarray, index, count);
1576 if (nr == 0)
1577 return 0;
1578
1579 actual = PAGE_SIZE * nr;
1580 actual -= offset;
1581 if (nr == count && size > 0) {
1582 unsigned last_offset = (nr > 1) ? 0 : offset;
1583 actual -= PAGE_SIZE - (last_offset + size);
1584 }
1585 return actual;
1586 }
1587
1588 ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,
1589 struct page ***pages, size_t maxsize,
1590 size_t *start)
1591 {
1592 struct page **p;
1593 size_t len;
1594 int n, res;
1595
1596 if (maxsize > i->count)
1597 maxsize = i->count;
1598 if (!maxsize)
1599 return 0;
1600
1601 if (likely(iter_is_iovec(i))) {
1602 unsigned long addr;
1603
1604 addr = first_iovec_segment(i, &len, start, maxsize, ~0U);
1605 n = DIV_ROUND_UP(len, PAGE_SIZE);
1606 p = get_pages_array(n);
1607 if (!p)
1608 return -ENOMEM;
1609 res = get_user_pages_fast(addr, n,
1610 iov_iter_rw(i) != WRITE ? FOLL_WRITE : 0, p);
1611 if (unlikely(res < 0)) {
1612 kvfree(p);
1613 return res;
1614 }
1615 *pages = p;
1616 return (res == n ? len : res * PAGE_SIZE) - *start;
1617 }
1618 if (iov_iter_is_bvec(i)) {
1619 struct page *page;
1620
1621 page = first_bvec_segment(i, &len, start, maxsize, ~0U);
1622 n = DIV_ROUND_UP(len, PAGE_SIZE);
1623 *pages = p = get_pages_array(n);
1624 if (!p)
1625 return -ENOMEM;
1626 while (n--)
1627 get_page(*p++ = page++);
1628 return len - *start;
1629 }
1630 if (iov_iter_is_pipe(i))
1631 return pipe_get_pages_alloc(i, pages, maxsize, start);
1632 if (iov_iter_is_xarray(i))
1633 return iter_xarray_get_pages_alloc(i, pages, maxsize, start);
1634 return -EFAULT;
1635 }
1636 EXPORT_SYMBOL(iov_iter_get_pages_alloc);
1637
1638 size_t csum_and_copy_from_iter(void *addr, size_t bytes, __wsum *csum,
1639 struct iov_iter *i)
1640 {
1641 __wsum sum, next;
1642 sum = *csum;
1643 if (unlikely(iov_iter_is_pipe(i) || iov_iter_is_discard(i))) {
1644 WARN_ON(1);
1645 return 0;
1646 }
1647 iterate_and_advance(i, bytes, base, len, off, ({
1648 next = csum_and_copy_from_user(base, addr + off, len);
1649 sum = csum_block_add(sum, next, off);
1650 next ? 0 : len;
1651 }), ({
1652 sum = csum_and_memcpy(addr + off, base, len, sum, off);
1653 })
1654 )
1655 *csum = sum;
1656 return bytes;
1657 }
1658 EXPORT_SYMBOL(csum_and_copy_from_iter);
1659
1660 size_t csum_and_copy_to_iter(const void *addr, size_t bytes, void *_csstate,
1661 struct iov_iter *i)
1662 {
1663 struct csum_state *csstate = _csstate;
1664 __wsum sum, next;
1665
1666 if (unlikely(iov_iter_is_discard(i))) {
1667 WARN_ON(1); /* for now */
1668 return 0;
1669 }
1670
1671 sum = csum_shift(csstate->csum, csstate->off);
1672 if (unlikely(iov_iter_is_pipe(i)))
1673 bytes = csum_and_copy_to_pipe_iter(addr, bytes, i, &sum);
1674 else iterate_and_advance(i, bytes, base, len, off, ({
1675 next = csum_and_copy_to_user(addr + off, base, len);
1676 sum = csum_block_add(sum, next, off);
1677 next ? 0 : len;
1678 }), ({
1679 sum = csum_and_memcpy(base, addr + off, len, sum, off);
1680 })
1681 )
1682 csstate->csum = csum_shift(sum, csstate->off);
1683 csstate->off += bytes;
1684 return bytes;
1685 }
1686 EXPORT_SYMBOL(csum_and_copy_to_iter);
1687
1688 size_t hash_and_copy_to_iter(const void *addr, size_t bytes, void *hashp,
1689 struct iov_iter *i)
1690 {
1691 #ifdef CONFIG_CRYPTO_HASH
1692 struct ahash_request *hash = hashp;
1693 struct scatterlist sg;
1694 size_t copied;
1695
1696 copied = copy_to_iter(addr, bytes, i);
1697 sg_init_one(&sg, addr, copied);
1698 ahash_request_set_crypt(hash, &sg, NULL, copied);
1699 crypto_ahash_update(hash);
1700 return copied;
1701 #else
1702 return 0;
1703 #endif
1704 }
1705 EXPORT_SYMBOL(hash_and_copy_to_iter);
1706
1707 static int iov_npages(const struct iov_iter *i, int maxpages)
1708 {
1709 size_t skip = i->iov_offset, size = i->count;
1710 const struct iovec *p;
1711 int npages = 0;
1712
1713 for (p = i->iov; size; skip = 0, p++) {
1714 unsigned offs = offset_in_page(p->iov_base + skip);
1715 size_t len = min(p->iov_len - skip, size);
1716
1717 if (len) {
1718 size -= len;
1719 npages += DIV_ROUND_UP(offs + len, PAGE_SIZE);
1720 if (unlikely(npages > maxpages))
1721 return maxpages;
1722 }
1723 }
1724 return npages;
1725 }
1726
1727 static int bvec_npages(const struct iov_iter *i, int maxpages)
1728 {
1729 size_t skip = i->iov_offset, size = i->count;
1730 const struct bio_vec *p;
1731 int npages = 0;
1732
1733 for (p = i->bvec; size; skip = 0, p++) {
1734 unsigned offs = (p->bv_offset + skip) % PAGE_SIZE;
1735 size_t len = min(p->bv_len - skip, size);
1736
1737 size -= len;
1738 npages += DIV_ROUND_UP(offs + len, PAGE_SIZE);
1739 if (unlikely(npages > maxpages))
1740 return maxpages;
1741 }
1742 return npages;
1743 }
1744
1745 int iov_iter_npages(const struct iov_iter *i, int maxpages)
1746 {
1747 if (unlikely(!i->count))
1748 return 0;
1749 /* iovec and kvec have identical layouts */
1750 if (likely(iter_is_iovec(i) || iov_iter_is_kvec(i)))
1751 return iov_npages(i, maxpages);
1752 if (iov_iter_is_bvec(i))
1753 return bvec_npages(i, maxpages);
1754 if (iov_iter_is_pipe(i)) {
1755 unsigned int iter_head;
1756 int npages;
1757 size_t off;
1758
1759 if (!sanity(i))
1760 return 0;
1761
1762 data_start(i, &iter_head, &off);
1763 /* some of this one + all after this one */
1764 npages = pipe_space_for_user(iter_head, i->pipe->tail, i->pipe);
1765 return min(npages, maxpages);
1766 }
1767 if (iov_iter_is_xarray(i)) {
1768 unsigned offset = (i->xarray_start + i->iov_offset) % PAGE_SIZE;
1769 int npages = DIV_ROUND_UP(offset + i->count, PAGE_SIZE);
1770 return min(npages, maxpages);
1771 }
1772 return 0;
1773 }
1774 EXPORT_SYMBOL(iov_iter_npages);
1775
1776 const void *dup_iter(struct iov_iter *new, struct iov_iter *old, gfp_t flags)
1777 {
1778 *new = *old;
1779 if (unlikely(iov_iter_is_pipe(new))) {
1780 WARN_ON(1);
1781 return NULL;
1782 }
1783 if (unlikely(iov_iter_is_discard(new) || iov_iter_is_xarray(new)))
1784 return NULL;
1785 if (iov_iter_is_bvec(new))
1786 return new->bvec = kmemdup(new->bvec,
1787 new->nr_segs * sizeof(struct bio_vec),
1788 flags);
1789 else
1790 /* iovec and kvec have identical layout */
1791 return new->iov = kmemdup(new->iov,
1792 new->nr_segs * sizeof(struct iovec),
1793 flags);
1794 }
1795 EXPORT_SYMBOL(dup_iter);
1796
1797 static int copy_compat_iovec_from_user(struct iovec *iov,
1798 const struct iovec __user *uvec, unsigned long nr_segs)
1799 {
1800 const struct compat_iovec __user *uiov =
1801 (const struct compat_iovec __user *)uvec;
1802 int ret = -EFAULT, i;
1803
1804 if (!user_access_begin(uiov, nr_segs * sizeof(*uiov)))
1805 return -EFAULT;
1806
1807 for (i = 0; i < nr_segs; i++) {
1808 compat_uptr_t buf;
1809 compat_ssize_t len;
1810
1811 unsafe_get_user(len, &uiov[i].iov_len, uaccess_end);
1812 unsafe_get_user(buf, &uiov[i].iov_base, uaccess_end);
1813
1814 /* check for compat_size_t not fitting in compat_ssize_t .. */
1815 if (len < 0) {
1816 ret = -EINVAL;
1817 goto uaccess_end;
1818 }
1819 iov[i].iov_base = compat_ptr(buf);
1820 iov[i].iov_len = len;
1821 }
1822
1823 ret = 0;
1824 uaccess_end:
1825 user_access_end();
1826 return ret;
1827 }
1828
1829 static int copy_iovec_from_user(struct iovec *iov,
1830 const struct iovec __user *uvec, unsigned long nr_segs)
1831 {
1832 unsigned long seg;
1833
1834 if (copy_from_user(iov, uvec, nr_segs * sizeof(*uvec)))
1835 return -EFAULT;
1836 for (seg = 0; seg < nr_segs; seg++) {
1837 if ((ssize_t)iov[seg].iov_len < 0)
1838 return -EINVAL;
1839 }
1840
1841 return 0;
1842 }
1843
1844 struct iovec *iovec_from_user(const struct iovec __user *uvec,
1845 unsigned long nr_segs, unsigned long fast_segs,
1846 struct iovec *fast_iov, bool compat)
1847 {
1848 struct iovec *iov = fast_iov;
1849 int ret;
1850
1851 /*
1852 * SuS says "The readv() function *may* fail if the iovcnt argument was
1853 * less than or equal to 0, or greater than {IOV_MAX}. Linux has
1854 * traditionally returned zero for zero segments, so...
1855 */
1856 if (nr_segs == 0)
1857 return iov;
1858 if (nr_segs > UIO_MAXIOV)
1859 return ERR_PTR(-EINVAL);
1860 if (nr_segs > fast_segs) {
1861 iov = kmalloc_array(nr_segs, sizeof(struct iovec), GFP_KERNEL);
1862 if (!iov)
1863 return ERR_PTR(-ENOMEM);
1864 }
1865
1866 if (compat)
1867 ret = copy_compat_iovec_from_user(iov, uvec, nr_segs);
1868 else
1869 ret = copy_iovec_from_user(iov, uvec, nr_segs);
1870 if (ret) {
1871 if (iov != fast_iov)
1872 kfree(iov);
1873 return ERR_PTR(ret);
1874 }
1875
1876 return iov;
1877 }
1878
1879 ssize_t __import_iovec(int type, const struct iovec __user *uvec,
1880 unsigned nr_segs, unsigned fast_segs, struct iovec **iovp,
1881 struct iov_iter *i, bool compat)
1882 {
1883 ssize_t total_len = 0;
1884 unsigned long seg;
1885 struct iovec *iov;
1886
1887 iov = iovec_from_user(uvec, nr_segs, fast_segs, *iovp, compat);
1888 if (IS_ERR(iov)) {
1889 *iovp = NULL;
1890 return PTR_ERR(iov);
1891 }
1892
1893 /*
1894 * According to the Single Unix Specification we should return EINVAL if
1895 * an element length is < 0 when cast to ssize_t or if the total length
1896 * would overflow the ssize_t return value of the system call.
1897 *
1898 * Linux caps all read/write calls to MAX_RW_COUNT, and avoids the
1899 * overflow case.
1900 */
1901 for (seg = 0; seg < nr_segs; seg++) {
1902 ssize_t len = (ssize_t)iov[seg].iov_len;
1903
1904 if (!access_ok(iov[seg].iov_base, len)) {
1905 if (iov != *iovp)
1906 kfree(iov);
1907 *iovp = NULL;
1908 return -EFAULT;
1909 }
1910
1911 if (len > MAX_RW_COUNT - total_len) {
1912 len = MAX_RW_COUNT - total_len;
1913 iov[seg].iov_len = len;
1914 }
1915 total_len += len;
1916 }
1917
1918 iov_iter_init(i, type, iov, nr_segs, total_len);
1919 if (iov == *iovp)
1920 *iovp = NULL;
1921 else
1922 *iovp = iov;
1923 return total_len;
1924 }
1925
1926 /**
1927 * import_iovec() - Copy an array of &struct iovec from userspace
1928 * into the kernel, check that it is valid, and initialize a new
1929 * &struct iov_iter iterator to access it.
1930 *
1931 * @type: One of %READ or %WRITE.
1932 * @uvec: Pointer to the userspace array.
1933 * @nr_segs: Number of elements in userspace array.
1934 * @fast_segs: Number of elements in @iov.
1935 * @iovp: (input and output parameter) Pointer to pointer to (usually small
1936 * on-stack) kernel array.
1937 * @i: Pointer to iterator that will be initialized on success.
1938 *
1939 * If the array pointed to by *@iov is large enough to hold all @nr_segs,
1940 * then this function places %NULL in *@iov on return. Otherwise, a new
1941 * array will be allocated and the result placed in *@iov. This means that
1942 * the caller may call kfree() on *@iov regardless of whether the small
1943 * on-stack array was used or not (and regardless of whether this function
1944 * returns an error or not).
1945 *
1946 * Return: Negative error code on error, bytes imported on success
1947 */
1948 ssize_t import_iovec(int type, const struct iovec __user *uvec,
1949 unsigned nr_segs, unsigned fast_segs,
1950 struct iovec **iovp, struct iov_iter *i)
1951 {
1952 return __import_iovec(type, uvec, nr_segs, fast_segs, iovp, i,
1953 in_compat_syscall());
1954 }
1955 EXPORT_SYMBOL(import_iovec);
1956
1957 int import_single_range(int rw, void __user *buf, size_t len,
1958 struct iovec *iov, struct iov_iter *i)
1959 {
1960 if (len > MAX_RW_COUNT)
1961 len = MAX_RW_COUNT;
1962 if (unlikely(!access_ok(buf, len)))
1963 return -EFAULT;
1964
1965 iov->iov_base = buf;
1966 iov->iov_len = len;
1967 iov_iter_init(i, rw, iov, 1, len);
1968 return 0;
1969 }
1970 EXPORT_SYMBOL(import_single_range);
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