1 | // SPDX-License-Identifier: GPL-2.0 |
2 | /* |
3 | * linux/fs/pipe.c |
4 | * |
5 | * Copyright (C) 1991, 1992, 1999 Linus Torvalds |
6 | */ |
7 | |
8 | #include <linux/mm.h> |
9 | #include <linux/file.h> |
10 | #include <linux/poll.h> |
11 | #include <linux/slab.h> |
12 | #include <linux/module.h> |
13 | #include <linux/init.h> |
14 | #include <linux/fs.h> |
15 | #include <linux/log2.h> |
16 | #include <linux/mount.h> |
17 | #include <linux/pseudo_fs.h> |
18 | #include <linux/magic.h> |
19 | #include <linux/pipe_fs_i.h> |
20 | #include <linux/uio.h> |
21 | #include <linux/highmem.h> |
22 | #include <linux/pagemap.h> |
23 | #include <linux/audit.h> |
24 | #include <linux/syscalls.h> |
25 | #include <linux/fcntl.h> |
26 | #include <linux/memcontrol.h> |
27 | #include <linux/watch_queue.h> |
28 | #include <linux/sysctl.h> |
29 | |
30 | #include <linux/uaccess.h> |
31 | #include <asm/ioctls.h> |
32 | |
33 | #include "internal.h" |
34 | |
35 | /* |
36 | * New pipe buffers will be restricted to this size while the user is exceeding |
37 | * their pipe buffer quota. The general pipe use case needs at least two |
38 | * buffers: one for data yet to be read, and one for new data. If this is less |
39 | * than two, then a write to a non-empty pipe may block even if the pipe is not |
40 | * full. This can occur with GNU make jobserver or similar uses of pipes as |
41 | * semaphores: multiple processes may be waiting to write tokens back to the |
42 | * pipe before reading tokens: https://lore.kernel.org/lkml/1628086770.5rn8p04n6j.none@localhost/. |
43 | * |
44 | * Users can reduce their pipe buffers with F_SETPIPE_SZ below this at their |
45 | * own risk, namely: pipe writes to non-full pipes may block until the pipe is |
46 | * emptied. |
47 | */ |
48 | #define PIPE_MIN_DEF_BUFFERS 2 |
49 | |
50 | /* |
51 | * The max size that a non-root user is allowed to grow the pipe. Can |
52 | * be set by root in /proc/sys/fs/pipe-max-size |
53 | */ |
54 | static unsigned int pipe_max_size = 1048576; |
55 | |
56 | /* Maximum allocatable pages per user. Hard limit is unset by default, soft |
57 | * matches default values. |
58 | */ |
59 | static unsigned long pipe_user_pages_hard; |
60 | static unsigned long pipe_user_pages_soft = PIPE_DEF_BUFFERS * INR_OPEN_CUR; |
61 | |
62 | /* |
63 | * We use head and tail indices that aren't masked off, except at the point of |
64 | * dereference, but rather they're allowed to wrap naturally. This means there |
65 | * isn't a dead spot in the buffer, but the ring has to be a power of two and |
66 | * <= 2^31. |
67 | * -- David Howells 2019-09-23. |
68 | * |
69 | * Reads with count = 0 should always return 0. |
70 | * -- Julian Bradfield 1999-06-07. |
71 | * |
72 | * FIFOs and Pipes now generate SIGIO for both readers and writers. |
73 | * -- Jeremy Elson <jelson@circlemud.org> 2001-08-16 |
74 | * |
75 | * pipe_read & write cleanup |
76 | * -- Manfred Spraul <manfred@colorfullife.com> 2002-05-09 |
77 | */ |
78 | |
79 | #define cmp_int(l, r) ((l > r) - (l < r)) |
80 | |
81 | #ifdef CONFIG_PROVE_LOCKING |
82 | static int pipe_lock_cmp_fn(const struct lockdep_map *a, |
83 | const struct lockdep_map *b) |
84 | { |
85 | return cmp_int((unsigned long) a, (unsigned long) b); |
86 | } |
87 | #endif |
88 | |
89 | void pipe_lock(struct pipe_inode_info *pipe) |
90 | { |
91 | if (pipe->files) |
92 | mutex_lock(&pipe->mutex); |
93 | } |
94 | EXPORT_SYMBOL(pipe_lock); |
95 | |
96 | void pipe_unlock(struct pipe_inode_info *pipe) |
97 | { |
98 | if (pipe->files) |
99 | mutex_unlock(lock: &pipe->mutex); |
100 | } |
101 | EXPORT_SYMBOL(pipe_unlock); |
102 | |
103 | void pipe_double_lock(struct pipe_inode_info *pipe1, |
104 | struct pipe_inode_info *pipe2) |
105 | { |
106 | BUG_ON(pipe1 == pipe2); |
107 | |
108 | if (pipe1 > pipe2) |
109 | swap(pipe1, pipe2); |
110 | |
111 | pipe_lock(pipe1); |
112 | pipe_lock(pipe2); |
113 | } |
114 | |
115 | static void anon_pipe_buf_release(struct pipe_inode_info *pipe, |
116 | struct pipe_buffer *buf) |
117 | { |
118 | struct page *page = buf->page; |
119 | |
120 | /* |
121 | * If nobody else uses this page, and we don't already have a |
122 | * temporary page, let's keep track of it as a one-deep |
123 | * allocation cache. (Otherwise just release our reference to it) |
124 | */ |
125 | if (page_count(page) == 1 && !pipe->tmp_page) |
126 | pipe->tmp_page = page; |
127 | else |
128 | put_page(page); |
129 | } |
130 | |
131 | static bool anon_pipe_buf_try_steal(struct pipe_inode_info *pipe, |
132 | struct pipe_buffer *buf) |
133 | { |
134 | struct page *page = buf->page; |
135 | |
136 | if (page_count(page) != 1) |
137 | return false; |
138 | memcg_kmem_uncharge_page(page, order: 0); |
139 | __SetPageLocked(page); |
140 | return true; |
141 | } |
142 | |
143 | /** |
144 | * generic_pipe_buf_try_steal - attempt to take ownership of a &pipe_buffer |
145 | * @pipe: the pipe that the buffer belongs to |
146 | * @buf: the buffer to attempt to steal |
147 | * |
148 | * Description: |
149 | * This function attempts to steal the &struct page attached to |
150 | * @buf. If successful, this function returns 0 and returns with |
151 | * the page locked. The caller may then reuse the page for whatever |
152 | * he wishes; the typical use is insertion into a different file |
153 | * page cache. |
154 | */ |
155 | bool generic_pipe_buf_try_steal(struct pipe_inode_info *pipe, |
156 | struct pipe_buffer *buf) |
157 | { |
158 | struct page *page = buf->page; |
159 | |
160 | /* |
161 | * A reference of one is golden, that means that the owner of this |
162 | * page is the only one holding a reference to it. lock the page |
163 | * and return OK. |
164 | */ |
165 | if (page_count(page) == 1) { |
166 | lock_page(page); |
167 | return true; |
168 | } |
169 | return false; |
170 | } |
171 | EXPORT_SYMBOL(generic_pipe_buf_try_steal); |
172 | |
173 | /** |
174 | * generic_pipe_buf_get - get a reference to a &struct pipe_buffer |
175 | * @pipe: the pipe that the buffer belongs to |
176 | * @buf: the buffer to get a reference to |
177 | * |
178 | * Description: |
179 | * This function grabs an extra reference to @buf. It's used in |
180 | * the tee() system call, when we duplicate the buffers in one |
181 | * pipe into another. |
182 | */ |
183 | bool generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf) |
184 | { |
185 | return try_get_page(page: buf->page); |
186 | } |
187 | EXPORT_SYMBOL(generic_pipe_buf_get); |
188 | |
189 | /** |
190 | * generic_pipe_buf_release - put a reference to a &struct pipe_buffer |
191 | * @pipe: the pipe that the buffer belongs to |
192 | * @buf: the buffer to put a reference to |
193 | * |
194 | * Description: |
195 | * This function releases a reference to @buf. |
196 | */ |
197 | void generic_pipe_buf_release(struct pipe_inode_info *pipe, |
198 | struct pipe_buffer *buf) |
199 | { |
200 | put_page(page: buf->page); |
201 | } |
202 | EXPORT_SYMBOL(generic_pipe_buf_release); |
203 | |
204 | static const struct pipe_buf_operations anon_pipe_buf_ops = { |
205 | .release = anon_pipe_buf_release, |
206 | .try_steal = anon_pipe_buf_try_steal, |
207 | .get = generic_pipe_buf_get, |
208 | }; |
209 | |
210 | /* Done while waiting without holding the pipe lock - thus the READ_ONCE() */ |
211 | static inline bool pipe_readable(const struct pipe_inode_info *pipe) |
212 | { |
213 | unsigned int head = READ_ONCE(pipe->head); |
214 | unsigned int tail = READ_ONCE(pipe->tail); |
215 | unsigned int writers = READ_ONCE(pipe->writers); |
216 | |
217 | return !pipe_empty(head, tail) || !writers; |
218 | } |
219 | |
220 | static inline unsigned int pipe_update_tail(struct pipe_inode_info *pipe, |
221 | struct pipe_buffer *buf, |
222 | unsigned int tail) |
223 | { |
224 | pipe_buf_release(pipe, buf); |
225 | |
226 | /* |
227 | * If the pipe has a watch_queue, we need additional protection |
228 | * by the spinlock because notifications get posted with only |
229 | * this spinlock, no mutex |
230 | */ |
231 | if (pipe_has_watch_queue(pipe)) { |
232 | spin_lock_irq(lock: &pipe->rd_wait.lock); |
233 | #ifdef CONFIG_WATCH_QUEUE |
234 | if (buf->flags & PIPE_BUF_FLAG_LOSS) |
235 | pipe->note_loss = true; |
236 | #endif |
237 | pipe->tail = ++tail; |
238 | spin_unlock_irq(lock: &pipe->rd_wait.lock); |
239 | return tail; |
240 | } |
241 | |
242 | /* |
243 | * Without a watch_queue, we can simply increment the tail |
244 | * without the spinlock - the mutex is enough. |
245 | */ |
246 | pipe->tail = ++tail; |
247 | return tail; |
248 | } |
249 | |
250 | static ssize_t |
251 | pipe_read(struct kiocb *iocb, struct iov_iter *to) |
252 | { |
253 | size_t total_len = iov_iter_count(i: to); |
254 | struct file *filp = iocb->ki_filp; |
255 | struct pipe_inode_info *pipe = filp->private_data; |
256 | bool was_full, wake_next_reader = false; |
257 | ssize_t ret; |
258 | |
259 | /* Null read succeeds. */ |
260 | if (unlikely(total_len == 0)) |
261 | return 0; |
262 | |
263 | ret = 0; |
264 | mutex_lock(&pipe->mutex); |
265 | |
266 | /* |
267 | * We only wake up writers if the pipe was full when we started |
268 | * reading in order to avoid unnecessary wakeups. |
269 | * |
270 | * But when we do wake up writers, we do so using a sync wakeup |
271 | * (WF_SYNC), because we want them to get going and generate more |
272 | * data for us. |
273 | */ |
274 | was_full = pipe_full(head: pipe->head, tail: pipe->tail, limit: pipe->max_usage); |
275 | for (;;) { |
276 | /* Read ->head with a barrier vs post_one_notification() */ |
277 | unsigned int head = smp_load_acquire(&pipe->head); |
278 | unsigned int tail = pipe->tail; |
279 | unsigned int mask = pipe->ring_size - 1; |
280 | |
281 | #ifdef CONFIG_WATCH_QUEUE |
282 | if (pipe->note_loss) { |
283 | struct watch_notification n; |
284 | |
285 | if (total_len < 8) { |
286 | if (ret == 0) |
287 | ret = -ENOBUFS; |
288 | break; |
289 | } |
290 | |
291 | n.type = WATCH_TYPE_META; |
292 | n.subtype = WATCH_META_LOSS_NOTIFICATION; |
293 | n.info = watch_sizeof(n); |
294 | if (copy_to_iter(addr: &n, bytes: sizeof(n), i: to) != sizeof(n)) { |
295 | if (ret == 0) |
296 | ret = -EFAULT; |
297 | break; |
298 | } |
299 | ret += sizeof(n); |
300 | total_len -= sizeof(n); |
301 | pipe->note_loss = false; |
302 | } |
303 | #endif |
304 | |
305 | if (!pipe_empty(head, tail)) { |
306 | struct pipe_buffer *buf = &pipe->bufs[tail & mask]; |
307 | size_t chars = buf->len; |
308 | size_t written; |
309 | int error; |
310 | |
311 | if (chars > total_len) { |
312 | if (buf->flags & PIPE_BUF_FLAG_WHOLE) { |
313 | if (ret == 0) |
314 | ret = -ENOBUFS; |
315 | break; |
316 | } |
317 | chars = total_len; |
318 | } |
319 | |
320 | error = pipe_buf_confirm(pipe, buf); |
321 | if (error) { |
322 | if (!ret) |
323 | ret = error; |
324 | break; |
325 | } |
326 | |
327 | written = copy_page_to_iter(page: buf->page, offset: buf->offset, bytes: chars, i: to); |
328 | if (unlikely(written < chars)) { |
329 | if (!ret) |
330 | ret = -EFAULT; |
331 | break; |
332 | } |
333 | ret += chars; |
334 | buf->offset += chars; |
335 | buf->len -= chars; |
336 | |
337 | /* Was it a packet buffer? Clean up and exit */ |
338 | if (buf->flags & PIPE_BUF_FLAG_PACKET) { |
339 | total_len = chars; |
340 | buf->len = 0; |
341 | } |
342 | |
343 | if (!buf->len) |
344 | tail = pipe_update_tail(pipe, buf, tail); |
345 | total_len -= chars; |
346 | if (!total_len) |
347 | break; /* common path: read succeeded */ |
348 | if (!pipe_empty(head, tail)) /* More to do? */ |
349 | continue; |
350 | } |
351 | |
352 | if (!pipe->writers) |
353 | break; |
354 | if (ret) |
355 | break; |
356 | if ((filp->f_flags & O_NONBLOCK) || |
357 | (iocb->ki_flags & IOCB_NOWAIT)) { |
358 | ret = -EAGAIN; |
359 | break; |
360 | } |
361 | mutex_unlock(lock: &pipe->mutex); |
362 | |
363 | /* |
364 | * We only get here if we didn't actually read anything. |
365 | * |
366 | * However, we could have seen (and removed) a zero-sized |
367 | * pipe buffer, and might have made space in the buffers |
368 | * that way. |
369 | * |
370 | * You can't make zero-sized pipe buffers by doing an empty |
371 | * write (not even in packet mode), but they can happen if |
372 | * the writer gets an EFAULT when trying to fill a buffer |
373 | * that already got allocated and inserted in the buffer |
374 | * array. |
375 | * |
376 | * So we still need to wake up any pending writers in the |
377 | * _very_ unlikely case that the pipe was full, but we got |
378 | * no data. |
379 | */ |
380 | if (unlikely(was_full)) |
381 | wake_up_interruptible_sync_poll(&pipe->wr_wait, EPOLLOUT | EPOLLWRNORM); |
382 | kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT); |
383 | |
384 | /* |
385 | * But because we didn't read anything, at this point we can |
386 | * just return directly with -ERESTARTSYS if we're interrupted, |
387 | * since we've done any required wakeups and there's no need |
388 | * to mark anything accessed. And we've dropped the lock. |
389 | */ |
390 | if (wait_event_interruptible_exclusive(pipe->rd_wait, pipe_readable(pipe)) < 0) |
391 | return -ERESTARTSYS; |
392 | |
393 | mutex_lock(&pipe->mutex); |
394 | was_full = pipe_full(head: pipe->head, tail: pipe->tail, limit: pipe->max_usage); |
395 | wake_next_reader = true; |
396 | } |
397 | if (pipe_empty(head: pipe->head, tail: pipe->tail)) |
398 | wake_next_reader = false; |
399 | mutex_unlock(lock: &pipe->mutex); |
400 | |
401 | if (was_full) |
402 | wake_up_interruptible_sync_poll(&pipe->wr_wait, EPOLLOUT | EPOLLWRNORM); |
403 | if (wake_next_reader) |
404 | wake_up_interruptible_sync_poll(&pipe->rd_wait, EPOLLIN | EPOLLRDNORM); |
405 | kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT); |
406 | if (ret > 0) |
407 | file_accessed(file: filp); |
408 | return ret; |
409 | } |
410 | |
411 | static inline int is_packetized(struct file *file) |
412 | { |
413 | return (file->f_flags & O_DIRECT) != 0; |
414 | } |
415 | |
416 | /* Done while waiting without holding the pipe lock - thus the READ_ONCE() */ |
417 | static inline bool pipe_writable(const struct pipe_inode_info *pipe) |
418 | { |
419 | unsigned int head = READ_ONCE(pipe->head); |
420 | unsigned int tail = READ_ONCE(pipe->tail); |
421 | unsigned int max_usage = READ_ONCE(pipe->max_usage); |
422 | |
423 | return !pipe_full(head, tail, limit: max_usage) || |
424 | !READ_ONCE(pipe->readers); |
425 | } |
426 | |
427 | static ssize_t |
428 | pipe_write(struct kiocb *iocb, struct iov_iter *from) |
429 | { |
430 | struct file *filp = iocb->ki_filp; |
431 | struct pipe_inode_info *pipe = filp->private_data; |
432 | unsigned int head; |
433 | ssize_t ret = 0; |
434 | size_t total_len = iov_iter_count(i: from); |
435 | ssize_t chars; |
436 | bool was_empty = false; |
437 | bool wake_next_writer = false; |
438 | |
439 | /* |
440 | * Reject writing to watch queue pipes before the point where we lock |
441 | * the pipe. |
442 | * Otherwise, lockdep would be unhappy if the caller already has another |
443 | * pipe locked. |
444 | * If we had to support locking a normal pipe and a notification pipe at |
445 | * the same time, we could set up lockdep annotations for that, but |
446 | * since we don't actually need that, it's simpler to just bail here. |
447 | */ |
448 | if (pipe_has_watch_queue(pipe)) |
449 | return -EXDEV; |
450 | |
451 | /* Null write succeeds. */ |
452 | if (unlikely(total_len == 0)) |
453 | return 0; |
454 | |
455 | mutex_lock(&pipe->mutex); |
456 | |
457 | if (!pipe->readers) { |
458 | send_sig(SIGPIPE, current, 0); |
459 | ret = -EPIPE; |
460 | goto out; |
461 | } |
462 | |
463 | /* |
464 | * If it wasn't empty we try to merge new data into |
465 | * the last buffer. |
466 | * |
467 | * That naturally merges small writes, but it also |
468 | * page-aligns the rest of the writes for large writes |
469 | * spanning multiple pages. |
470 | */ |
471 | head = pipe->head; |
472 | was_empty = pipe_empty(head, tail: pipe->tail); |
473 | chars = total_len & (PAGE_SIZE-1); |
474 | if (chars && !was_empty) { |
475 | unsigned int mask = pipe->ring_size - 1; |
476 | struct pipe_buffer *buf = &pipe->bufs[(head - 1) & mask]; |
477 | int offset = buf->offset + buf->len; |
478 | |
479 | if ((buf->flags & PIPE_BUF_FLAG_CAN_MERGE) && |
480 | offset + chars <= PAGE_SIZE) { |
481 | ret = pipe_buf_confirm(pipe, buf); |
482 | if (ret) |
483 | goto out; |
484 | |
485 | ret = copy_page_from_iter(page: buf->page, offset, bytes: chars, i: from); |
486 | if (unlikely(ret < chars)) { |
487 | ret = -EFAULT; |
488 | goto out; |
489 | } |
490 | |
491 | buf->len += ret; |
492 | if (!iov_iter_count(i: from)) |
493 | goto out; |
494 | } |
495 | } |
496 | |
497 | for (;;) { |
498 | if (!pipe->readers) { |
499 | send_sig(SIGPIPE, current, 0); |
500 | if (!ret) |
501 | ret = -EPIPE; |
502 | break; |
503 | } |
504 | |
505 | head = pipe->head; |
506 | if (!pipe_full(head, tail: pipe->tail, limit: pipe->max_usage)) { |
507 | unsigned int mask = pipe->ring_size - 1; |
508 | struct pipe_buffer *buf; |
509 | struct page *page = pipe->tmp_page; |
510 | int copied; |
511 | |
512 | if (!page) { |
513 | page = alloc_page(GFP_HIGHUSER | __GFP_ACCOUNT); |
514 | if (unlikely(!page)) { |
515 | ret = ret ? : -ENOMEM; |
516 | break; |
517 | } |
518 | pipe->tmp_page = page; |
519 | } |
520 | |
521 | /* Allocate a slot in the ring in advance and attach an |
522 | * empty buffer. If we fault or otherwise fail to use |
523 | * it, either the reader will consume it or it'll still |
524 | * be there for the next write. |
525 | */ |
526 | pipe->head = head + 1; |
527 | |
528 | /* Insert it into the buffer array */ |
529 | buf = &pipe->bufs[head & mask]; |
530 | buf->page = page; |
531 | buf->ops = &anon_pipe_buf_ops; |
532 | buf->offset = 0; |
533 | buf->len = 0; |
534 | if (is_packetized(file: filp)) |
535 | buf->flags = PIPE_BUF_FLAG_PACKET; |
536 | else |
537 | buf->flags = PIPE_BUF_FLAG_CAN_MERGE; |
538 | pipe->tmp_page = NULL; |
539 | |
540 | copied = copy_page_from_iter(page, offset: 0, PAGE_SIZE, i: from); |
541 | if (unlikely(copied < PAGE_SIZE && iov_iter_count(from))) { |
542 | if (!ret) |
543 | ret = -EFAULT; |
544 | break; |
545 | } |
546 | ret += copied; |
547 | buf->len = copied; |
548 | |
549 | if (!iov_iter_count(i: from)) |
550 | break; |
551 | } |
552 | |
553 | if (!pipe_full(head, tail: pipe->tail, limit: pipe->max_usage)) |
554 | continue; |
555 | |
556 | /* Wait for buffer space to become available. */ |
557 | if ((filp->f_flags & O_NONBLOCK) || |
558 | (iocb->ki_flags & IOCB_NOWAIT)) { |
559 | if (!ret) |
560 | ret = -EAGAIN; |
561 | break; |
562 | } |
563 | if (signal_pending(current)) { |
564 | if (!ret) |
565 | ret = -ERESTARTSYS; |
566 | break; |
567 | } |
568 | |
569 | /* |
570 | * We're going to release the pipe lock and wait for more |
571 | * space. We wake up any readers if necessary, and then |
572 | * after waiting we need to re-check whether the pipe |
573 | * become empty while we dropped the lock. |
574 | */ |
575 | mutex_unlock(lock: &pipe->mutex); |
576 | if (was_empty) |
577 | wake_up_interruptible_sync_poll(&pipe->rd_wait, EPOLLIN | EPOLLRDNORM); |
578 | kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN); |
579 | wait_event_interruptible_exclusive(pipe->wr_wait, pipe_writable(pipe)); |
580 | mutex_lock(&pipe->mutex); |
581 | was_empty = pipe_empty(head: pipe->head, tail: pipe->tail); |
582 | wake_next_writer = true; |
583 | } |
584 | out: |
585 | if (pipe_full(head: pipe->head, tail: pipe->tail, limit: pipe->max_usage)) |
586 | wake_next_writer = false; |
587 | mutex_unlock(lock: &pipe->mutex); |
588 | |
589 | /* |
590 | * If we do do a wakeup event, we do a 'sync' wakeup, because we |
591 | * want the reader to start processing things asap, rather than |
592 | * leave the data pending. |
593 | * |
594 | * This is particularly important for small writes, because of |
595 | * how (for example) the GNU make jobserver uses small writes to |
596 | * wake up pending jobs |
597 | * |
598 | * Epoll nonsensically wants a wakeup whether the pipe |
599 | * was already empty or not. |
600 | */ |
601 | if (was_empty || pipe->poll_usage) |
602 | wake_up_interruptible_sync_poll(&pipe->rd_wait, EPOLLIN | EPOLLRDNORM); |
603 | kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN); |
604 | if (wake_next_writer) |
605 | wake_up_interruptible_sync_poll(&pipe->wr_wait, EPOLLOUT | EPOLLWRNORM); |
606 | if (ret > 0 && sb_start_write_trylock(sb: file_inode(f: filp)->i_sb)) { |
607 | int err = file_update_time(file: filp); |
608 | if (err) |
609 | ret = err; |
610 | sb_end_write(sb: file_inode(f: filp)->i_sb); |
611 | } |
612 | return ret; |
613 | } |
614 | |
615 | static long pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) |
616 | { |
617 | struct pipe_inode_info *pipe = filp->private_data; |
618 | unsigned int count, head, tail, mask; |
619 | |
620 | switch (cmd) { |
621 | case FIONREAD: |
622 | mutex_lock(&pipe->mutex); |
623 | count = 0; |
624 | head = pipe->head; |
625 | tail = pipe->tail; |
626 | mask = pipe->ring_size - 1; |
627 | |
628 | while (tail != head) { |
629 | count += pipe->bufs[tail & mask].len; |
630 | tail++; |
631 | } |
632 | mutex_unlock(lock: &pipe->mutex); |
633 | |
634 | return put_user(count, (int __user *)arg); |
635 | |
636 | #ifdef CONFIG_WATCH_QUEUE |
637 | case IOC_WATCH_QUEUE_SET_SIZE: { |
638 | int ret; |
639 | mutex_lock(&pipe->mutex); |
640 | ret = watch_queue_set_size(pipe, arg); |
641 | mutex_unlock(lock: &pipe->mutex); |
642 | return ret; |
643 | } |
644 | |
645 | case IOC_WATCH_QUEUE_SET_FILTER: |
646 | return watch_queue_set_filter( |
647 | pipe, (struct watch_notification_filter __user *)arg); |
648 | #endif |
649 | |
650 | default: |
651 | return -ENOIOCTLCMD; |
652 | } |
653 | } |
654 | |
655 | /* No kernel lock held - fine */ |
656 | static __poll_t |
657 | pipe_poll(struct file *filp, poll_table *wait) |
658 | { |
659 | __poll_t mask; |
660 | struct pipe_inode_info *pipe = filp->private_data; |
661 | unsigned int head, tail; |
662 | |
663 | /* Epoll has some historical nasty semantics, this enables them */ |
664 | WRITE_ONCE(pipe->poll_usage, true); |
665 | |
666 | /* |
667 | * Reading pipe state only -- no need for acquiring the semaphore. |
668 | * |
669 | * But because this is racy, the code has to add the |
670 | * entry to the poll table _first_ .. |
671 | */ |
672 | if (filp->f_mode & FMODE_READ) |
673 | poll_wait(filp, wait_address: &pipe->rd_wait, p: wait); |
674 | if (filp->f_mode & FMODE_WRITE) |
675 | poll_wait(filp, wait_address: &pipe->wr_wait, p: wait); |
676 | |
677 | /* |
678 | * .. and only then can you do the racy tests. That way, |
679 | * if something changes and you got it wrong, the poll |
680 | * table entry will wake you up and fix it. |
681 | */ |
682 | head = READ_ONCE(pipe->head); |
683 | tail = READ_ONCE(pipe->tail); |
684 | |
685 | mask = 0; |
686 | if (filp->f_mode & FMODE_READ) { |
687 | if (!pipe_empty(head, tail)) |
688 | mask |= EPOLLIN | EPOLLRDNORM; |
689 | if (!pipe->writers && filp->f_version != pipe->w_counter) |
690 | mask |= EPOLLHUP; |
691 | } |
692 | |
693 | if (filp->f_mode & FMODE_WRITE) { |
694 | if (!pipe_full(head, tail, limit: pipe->max_usage)) |
695 | mask |= EPOLLOUT | EPOLLWRNORM; |
696 | /* |
697 | * Most Unices do not set EPOLLERR for FIFOs but on Linux they |
698 | * behave exactly like pipes for poll(). |
699 | */ |
700 | if (!pipe->readers) |
701 | mask |= EPOLLERR; |
702 | } |
703 | |
704 | return mask; |
705 | } |
706 | |
707 | static void put_pipe_info(struct inode *inode, struct pipe_inode_info *pipe) |
708 | { |
709 | int kill = 0; |
710 | |
711 | spin_lock(lock: &inode->i_lock); |
712 | if (!--pipe->files) { |
713 | inode->i_pipe = NULL; |
714 | kill = 1; |
715 | } |
716 | spin_unlock(lock: &inode->i_lock); |
717 | |
718 | if (kill) |
719 | free_pipe_info(pipe); |
720 | } |
721 | |
722 | static int |
723 | pipe_release(struct inode *inode, struct file *file) |
724 | { |
725 | struct pipe_inode_info *pipe = file->private_data; |
726 | |
727 | mutex_lock(&pipe->mutex); |
728 | if (file->f_mode & FMODE_READ) |
729 | pipe->readers--; |
730 | if (file->f_mode & FMODE_WRITE) |
731 | pipe->writers--; |
732 | |
733 | /* Was that the last reader or writer, but not the other side? */ |
734 | if (!pipe->readers != !pipe->writers) { |
735 | wake_up_interruptible_all(&pipe->rd_wait); |
736 | wake_up_interruptible_all(&pipe->wr_wait); |
737 | kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN); |
738 | kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT); |
739 | } |
740 | mutex_unlock(lock: &pipe->mutex); |
741 | |
742 | put_pipe_info(inode, pipe); |
743 | return 0; |
744 | } |
745 | |
746 | static int |
747 | pipe_fasync(int fd, struct file *filp, int on) |
748 | { |
749 | struct pipe_inode_info *pipe = filp->private_data; |
750 | int retval = 0; |
751 | |
752 | mutex_lock(&pipe->mutex); |
753 | if (filp->f_mode & FMODE_READ) |
754 | retval = fasync_helper(fd, filp, on, &pipe->fasync_readers); |
755 | if ((filp->f_mode & FMODE_WRITE) && retval >= 0) { |
756 | retval = fasync_helper(fd, filp, on, &pipe->fasync_writers); |
757 | if (retval < 0 && (filp->f_mode & FMODE_READ)) |
758 | /* this can happen only if on == T */ |
759 | fasync_helper(-1, filp, 0, &pipe->fasync_readers); |
760 | } |
761 | mutex_unlock(lock: &pipe->mutex); |
762 | return retval; |
763 | } |
764 | |
765 | unsigned long account_pipe_buffers(struct user_struct *user, |
766 | unsigned long old, unsigned long new) |
767 | { |
768 | return atomic_long_add_return(i: new - old, v: &user->pipe_bufs); |
769 | } |
770 | |
771 | bool too_many_pipe_buffers_soft(unsigned long user_bufs) |
772 | { |
773 | unsigned long soft_limit = READ_ONCE(pipe_user_pages_soft); |
774 | |
775 | return soft_limit && user_bufs > soft_limit; |
776 | } |
777 | |
778 | bool too_many_pipe_buffers_hard(unsigned long user_bufs) |
779 | { |
780 | unsigned long hard_limit = READ_ONCE(pipe_user_pages_hard); |
781 | |
782 | return hard_limit && user_bufs > hard_limit; |
783 | } |
784 | |
785 | bool pipe_is_unprivileged_user(void) |
786 | { |
787 | return !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN); |
788 | } |
789 | |
790 | struct pipe_inode_info *alloc_pipe_info(void) |
791 | { |
792 | struct pipe_inode_info *pipe; |
793 | unsigned long pipe_bufs = PIPE_DEF_BUFFERS; |
794 | struct user_struct *user = get_current_user(); |
795 | unsigned long user_bufs; |
796 | unsigned int max_size = READ_ONCE(pipe_max_size); |
797 | |
798 | pipe = kzalloc(size: sizeof(struct pipe_inode_info), GFP_KERNEL_ACCOUNT); |
799 | if (pipe == NULL) |
800 | goto out_free_uid; |
801 | |
802 | if (pipe_bufs * PAGE_SIZE > max_size && !capable(CAP_SYS_RESOURCE)) |
803 | pipe_bufs = max_size >> PAGE_SHIFT; |
804 | |
805 | user_bufs = account_pipe_buffers(user, old: 0, new: pipe_bufs); |
806 | |
807 | if (too_many_pipe_buffers_soft(user_bufs) && pipe_is_unprivileged_user()) { |
808 | user_bufs = account_pipe_buffers(user, old: pipe_bufs, PIPE_MIN_DEF_BUFFERS); |
809 | pipe_bufs = PIPE_MIN_DEF_BUFFERS; |
810 | } |
811 | |
812 | if (too_many_pipe_buffers_hard(user_bufs) && pipe_is_unprivileged_user()) |
813 | goto out_revert_acct; |
814 | |
815 | pipe->bufs = kcalloc(n: pipe_bufs, size: sizeof(struct pipe_buffer), |
816 | GFP_KERNEL_ACCOUNT); |
817 | |
818 | if (pipe->bufs) { |
819 | init_waitqueue_head(&pipe->rd_wait); |
820 | init_waitqueue_head(&pipe->wr_wait); |
821 | pipe->r_counter = pipe->w_counter = 1; |
822 | pipe->max_usage = pipe_bufs; |
823 | pipe->ring_size = pipe_bufs; |
824 | pipe->nr_accounted = pipe_bufs; |
825 | pipe->user = user; |
826 | mutex_init(&pipe->mutex); |
827 | lock_set_cmp_fn(&pipe->mutex, pipe_lock_cmp_fn, NULL); |
828 | return pipe; |
829 | } |
830 | |
831 | out_revert_acct: |
832 | (void) account_pipe_buffers(user, old: pipe_bufs, new: 0); |
833 | kfree(objp: pipe); |
834 | out_free_uid: |
835 | free_uid(user); |
836 | return NULL; |
837 | } |
838 | |
839 | void free_pipe_info(struct pipe_inode_info *pipe) |
840 | { |
841 | unsigned int i; |
842 | |
843 | #ifdef CONFIG_WATCH_QUEUE |
844 | if (pipe->watch_queue) |
845 | watch_queue_clear(pipe->watch_queue); |
846 | #endif |
847 | |
848 | (void) account_pipe_buffers(user: pipe->user, old: pipe->nr_accounted, new: 0); |
849 | free_uid(pipe->user); |
850 | for (i = 0; i < pipe->ring_size; i++) { |
851 | struct pipe_buffer *buf = pipe->bufs + i; |
852 | if (buf->ops) |
853 | pipe_buf_release(pipe, buf); |
854 | } |
855 | #ifdef CONFIG_WATCH_QUEUE |
856 | if (pipe->watch_queue) |
857 | put_watch_queue(pipe->watch_queue); |
858 | #endif |
859 | if (pipe->tmp_page) |
860 | __free_page(pipe->tmp_page); |
861 | kfree(objp: pipe->bufs); |
862 | kfree(objp: pipe); |
863 | } |
864 | |
865 | static struct vfsmount *pipe_mnt __ro_after_init; |
866 | |
867 | /* |
868 | * pipefs_dname() is called from d_path(). |
869 | */ |
870 | static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen) |
871 | { |
872 | return dynamic_dname(buffer, buflen, "pipe:[%lu]" , |
873 | d_inode(dentry)->i_ino); |
874 | } |
875 | |
876 | static const struct dentry_operations pipefs_dentry_operations = { |
877 | .d_dname = pipefs_dname, |
878 | }; |
879 | |
880 | static struct inode * get_pipe_inode(void) |
881 | { |
882 | struct inode *inode = new_inode_pseudo(sb: pipe_mnt->mnt_sb); |
883 | struct pipe_inode_info *pipe; |
884 | |
885 | if (!inode) |
886 | goto fail_inode; |
887 | |
888 | inode->i_ino = get_next_ino(); |
889 | |
890 | pipe = alloc_pipe_info(); |
891 | if (!pipe) |
892 | goto fail_iput; |
893 | |
894 | inode->i_pipe = pipe; |
895 | pipe->files = 2; |
896 | pipe->readers = pipe->writers = 1; |
897 | inode->i_fop = &pipefifo_fops; |
898 | |
899 | /* |
900 | * Mark the inode dirty from the very beginning, |
901 | * that way it will never be moved to the dirty |
902 | * list because "mark_inode_dirty()" will think |
903 | * that it already _is_ on the dirty list. |
904 | */ |
905 | inode->i_state = I_DIRTY; |
906 | inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR; |
907 | inode->i_uid = current_fsuid(); |
908 | inode->i_gid = current_fsgid(); |
909 | simple_inode_init_ts(inode); |
910 | |
911 | return inode; |
912 | |
913 | fail_iput: |
914 | iput(inode); |
915 | |
916 | fail_inode: |
917 | return NULL; |
918 | } |
919 | |
920 | int create_pipe_files(struct file **res, int flags) |
921 | { |
922 | struct inode *inode = get_pipe_inode(); |
923 | struct file *f; |
924 | int error; |
925 | |
926 | if (!inode) |
927 | return -ENFILE; |
928 | |
929 | if (flags & O_NOTIFICATION_PIPE) { |
930 | error = watch_queue_init(inode->i_pipe); |
931 | if (error) { |
932 | free_pipe_info(pipe: inode->i_pipe); |
933 | iput(inode); |
934 | return error; |
935 | } |
936 | } |
937 | |
938 | f = alloc_file_pseudo(inode, pipe_mnt, "" , |
939 | O_WRONLY | (flags & (O_NONBLOCK | O_DIRECT)), |
940 | &pipefifo_fops); |
941 | if (IS_ERR(ptr: f)) { |
942 | free_pipe_info(pipe: inode->i_pipe); |
943 | iput(inode); |
944 | return PTR_ERR(ptr: f); |
945 | } |
946 | |
947 | f->private_data = inode->i_pipe; |
948 | |
949 | res[0] = alloc_file_clone(f, O_RDONLY | (flags & O_NONBLOCK), |
950 | &pipefifo_fops); |
951 | if (IS_ERR(ptr: res[0])) { |
952 | put_pipe_info(inode, pipe: inode->i_pipe); |
953 | fput(f); |
954 | return PTR_ERR(ptr: res[0]); |
955 | } |
956 | res[0]->private_data = inode->i_pipe; |
957 | res[1] = f; |
958 | stream_open(inode, filp: res[0]); |
959 | stream_open(inode, filp: res[1]); |
960 | return 0; |
961 | } |
962 | |
963 | static int __do_pipe_flags(int *fd, struct file **files, int flags) |
964 | { |
965 | int error; |
966 | int fdw, fdr; |
967 | |
968 | if (flags & ~(O_CLOEXEC | O_NONBLOCK | O_DIRECT | O_NOTIFICATION_PIPE)) |
969 | return -EINVAL; |
970 | |
971 | error = create_pipe_files(res: files, flags); |
972 | if (error) |
973 | return error; |
974 | |
975 | error = get_unused_fd_flags(flags); |
976 | if (error < 0) |
977 | goto err_read_pipe; |
978 | fdr = error; |
979 | |
980 | error = get_unused_fd_flags(flags); |
981 | if (error < 0) |
982 | goto err_fdr; |
983 | fdw = error; |
984 | |
985 | audit_fd_pair(fd1: fdr, fd2: fdw); |
986 | fd[0] = fdr; |
987 | fd[1] = fdw; |
988 | /* pipe groks IOCB_NOWAIT */ |
989 | files[0]->f_mode |= FMODE_NOWAIT; |
990 | files[1]->f_mode |= FMODE_NOWAIT; |
991 | return 0; |
992 | |
993 | err_fdr: |
994 | put_unused_fd(fd: fdr); |
995 | err_read_pipe: |
996 | fput(files[0]); |
997 | fput(files[1]); |
998 | return error; |
999 | } |
1000 | |
1001 | int do_pipe_flags(int *fd, int flags) |
1002 | { |
1003 | struct file *files[2]; |
1004 | int error = __do_pipe_flags(fd, files, flags); |
1005 | if (!error) { |
1006 | fd_install(fd: fd[0], file: files[0]); |
1007 | fd_install(fd: fd[1], file: files[1]); |
1008 | } |
1009 | return error; |
1010 | } |
1011 | |
1012 | /* |
1013 | * sys_pipe() is the normal C calling standard for creating |
1014 | * a pipe. It's not the way Unix traditionally does this, though. |
1015 | */ |
1016 | static int do_pipe2(int __user *fildes, int flags) |
1017 | { |
1018 | struct file *files[2]; |
1019 | int fd[2]; |
1020 | int error; |
1021 | |
1022 | error = __do_pipe_flags(fd, files, flags); |
1023 | if (!error) { |
1024 | if (unlikely(copy_to_user(fildes, fd, sizeof(fd)))) { |
1025 | fput(files[0]); |
1026 | fput(files[1]); |
1027 | put_unused_fd(fd: fd[0]); |
1028 | put_unused_fd(fd: fd[1]); |
1029 | error = -EFAULT; |
1030 | } else { |
1031 | fd_install(fd: fd[0], file: files[0]); |
1032 | fd_install(fd: fd[1], file: files[1]); |
1033 | } |
1034 | } |
1035 | return error; |
1036 | } |
1037 | |
1038 | SYSCALL_DEFINE2(pipe2, int __user *, fildes, int, flags) |
1039 | { |
1040 | return do_pipe2(fildes, flags); |
1041 | } |
1042 | |
1043 | SYSCALL_DEFINE1(pipe, int __user *, fildes) |
1044 | { |
1045 | return do_pipe2(fildes, flags: 0); |
1046 | } |
1047 | |
1048 | /* |
1049 | * This is the stupid "wait for pipe to be readable or writable" |
1050 | * model. |
1051 | * |
1052 | * See pipe_read/write() for the proper kind of exclusive wait, |
1053 | * but that requires that we wake up any other readers/writers |
1054 | * if we then do not end up reading everything (ie the whole |
1055 | * "wake_next_reader/writer" logic in pipe_read/write()). |
1056 | */ |
1057 | void pipe_wait_readable(struct pipe_inode_info *pipe) |
1058 | { |
1059 | pipe_unlock(pipe); |
1060 | wait_event_interruptible(pipe->rd_wait, pipe_readable(pipe)); |
1061 | pipe_lock(pipe); |
1062 | } |
1063 | |
1064 | void pipe_wait_writable(struct pipe_inode_info *pipe) |
1065 | { |
1066 | pipe_unlock(pipe); |
1067 | wait_event_interruptible(pipe->wr_wait, pipe_writable(pipe)); |
1068 | pipe_lock(pipe); |
1069 | } |
1070 | |
1071 | /* |
1072 | * This depends on both the wait (here) and the wakeup (wake_up_partner) |
1073 | * holding the pipe lock, so "*cnt" is stable and we know a wakeup cannot |
1074 | * race with the count check and waitqueue prep. |
1075 | * |
1076 | * Normally in order to avoid races, you'd do the prepare_to_wait() first, |
1077 | * then check the condition you're waiting for, and only then sleep. But |
1078 | * because of the pipe lock, we can check the condition before being on |
1079 | * the wait queue. |
1080 | * |
1081 | * We use the 'rd_wait' waitqueue for pipe partner waiting. |
1082 | */ |
1083 | static int wait_for_partner(struct pipe_inode_info *pipe, unsigned int *cnt) |
1084 | { |
1085 | DEFINE_WAIT(rdwait); |
1086 | int cur = *cnt; |
1087 | |
1088 | while (cur == *cnt) { |
1089 | prepare_to_wait(wq_head: &pipe->rd_wait, wq_entry: &rdwait, TASK_INTERRUPTIBLE); |
1090 | pipe_unlock(pipe); |
1091 | schedule(); |
1092 | finish_wait(wq_head: &pipe->rd_wait, wq_entry: &rdwait); |
1093 | pipe_lock(pipe); |
1094 | if (signal_pending(current)) |
1095 | break; |
1096 | } |
1097 | return cur == *cnt ? -ERESTARTSYS : 0; |
1098 | } |
1099 | |
1100 | static void wake_up_partner(struct pipe_inode_info *pipe) |
1101 | { |
1102 | wake_up_interruptible_all(&pipe->rd_wait); |
1103 | } |
1104 | |
1105 | static int fifo_open(struct inode *inode, struct file *filp) |
1106 | { |
1107 | struct pipe_inode_info *pipe; |
1108 | bool is_pipe = inode->i_sb->s_magic == PIPEFS_MAGIC; |
1109 | int ret; |
1110 | |
1111 | filp->f_version = 0; |
1112 | |
1113 | spin_lock(lock: &inode->i_lock); |
1114 | if (inode->i_pipe) { |
1115 | pipe = inode->i_pipe; |
1116 | pipe->files++; |
1117 | spin_unlock(lock: &inode->i_lock); |
1118 | } else { |
1119 | spin_unlock(lock: &inode->i_lock); |
1120 | pipe = alloc_pipe_info(); |
1121 | if (!pipe) |
1122 | return -ENOMEM; |
1123 | pipe->files = 1; |
1124 | spin_lock(lock: &inode->i_lock); |
1125 | if (unlikely(inode->i_pipe)) { |
1126 | inode->i_pipe->files++; |
1127 | spin_unlock(lock: &inode->i_lock); |
1128 | free_pipe_info(pipe); |
1129 | pipe = inode->i_pipe; |
1130 | } else { |
1131 | inode->i_pipe = pipe; |
1132 | spin_unlock(lock: &inode->i_lock); |
1133 | } |
1134 | } |
1135 | filp->private_data = pipe; |
1136 | /* OK, we have a pipe and it's pinned down */ |
1137 | |
1138 | mutex_lock(&pipe->mutex); |
1139 | |
1140 | /* We can only do regular read/write on fifos */ |
1141 | stream_open(inode, filp); |
1142 | |
1143 | switch (filp->f_mode & (FMODE_READ | FMODE_WRITE)) { |
1144 | case FMODE_READ: |
1145 | /* |
1146 | * O_RDONLY |
1147 | * POSIX.1 says that O_NONBLOCK means return with the FIFO |
1148 | * opened, even when there is no process writing the FIFO. |
1149 | */ |
1150 | pipe->r_counter++; |
1151 | if (pipe->readers++ == 0) |
1152 | wake_up_partner(pipe); |
1153 | |
1154 | if (!is_pipe && !pipe->writers) { |
1155 | if ((filp->f_flags & O_NONBLOCK)) { |
1156 | /* suppress EPOLLHUP until we have |
1157 | * seen a writer */ |
1158 | filp->f_version = pipe->w_counter; |
1159 | } else { |
1160 | if (wait_for_partner(pipe, cnt: &pipe->w_counter)) |
1161 | goto err_rd; |
1162 | } |
1163 | } |
1164 | break; |
1165 | |
1166 | case FMODE_WRITE: |
1167 | /* |
1168 | * O_WRONLY |
1169 | * POSIX.1 says that O_NONBLOCK means return -1 with |
1170 | * errno=ENXIO when there is no process reading the FIFO. |
1171 | */ |
1172 | ret = -ENXIO; |
1173 | if (!is_pipe && (filp->f_flags & O_NONBLOCK) && !pipe->readers) |
1174 | goto err; |
1175 | |
1176 | pipe->w_counter++; |
1177 | if (!pipe->writers++) |
1178 | wake_up_partner(pipe); |
1179 | |
1180 | if (!is_pipe && !pipe->readers) { |
1181 | if (wait_for_partner(pipe, cnt: &pipe->r_counter)) |
1182 | goto err_wr; |
1183 | } |
1184 | break; |
1185 | |
1186 | case FMODE_READ | FMODE_WRITE: |
1187 | /* |
1188 | * O_RDWR |
1189 | * POSIX.1 leaves this case "undefined" when O_NONBLOCK is set. |
1190 | * This implementation will NEVER block on a O_RDWR open, since |
1191 | * the process can at least talk to itself. |
1192 | */ |
1193 | |
1194 | pipe->readers++; |
1195 | pipe->writers++; |
1196 | pipe->r_counter++; |
1197 | pipe->w_counter++; |
1198 | if (pipe->readers == 1 || pipe->writers == 1) |
1199 | wake_up_partner(pipe); |
1200 | break; |
1201 | |
1202 | default: |
1203 | ret = -EINVAL; |
1204 | goto err; |
1205 | } |
1206 | |
1207 | /* Ok! */ |
1208 | mutex_unlock(lock: &pipe->mutex); |
1209 | return 0; |
1210 | |
1211 | err_rd: |
1212 | if (!--pipe->readers) |
1213 | wake_up_interruptible(&pipe->wr_wait); |
1214 | ret = -ERESTARTSYS; |
1215 | goto err; |
1216 | |
1217 | err_wr: |
1218 | if (!--pipe->writers) |
1219 | wake_up_interruptible_all(&pipe->rd_wait); |
1220 | ret = -ERESTARTSYS; |
1221 | goto err; |
1222 | |
1223 | err: |
1224 | mutex_unlock(lock: &pipe->mutex); |
1225 | |
1226 | put_pipe_info(inode, pipe); |
1227 | return ret; |
1228 | } |
1229 | |
1230 | const struct file_operations pipefifo_fops = { |
1231 | .open = fifo_open, |
1232 | .llseek = no_llseek, |
1233 | .read_iter = pipe_read, |
1234 | .write_iter = pipe_write, |
1235 | .poll = pipe_poll, |
1236 | .unlocked_ioctl = pipe_ioctl, |
1237 | .release = pipe_release, |
1238 | .fasync = pipe_fasync, |
1239 | .splice_write = iter_file_splice_write, |
1240 | }; |
1241 | |
1242 | /* |
1243 | * Currently we rely on the pipe array holding a power-of-2 number |
1244 | * of pages. Returns 0 on error. |
1245 | */ |
1246 | unsigned int round_pipe_size(unsigned int size) |
1247 | { |
1248 | if (size > (1U << 31)) |
1249 | return 0; |
1250 | |
1251 | /* Minimum pipe size, as required by POSIX */ |
1252 | if (size < PAGE_SIZE) |
1253 | return PAGE_SIZE; |
1254 | |
1255 | return roundup_pow_of_two(size); |
1256 | } |
1257 | |
1258 | /* |
1259 | * Resize the pipe ring to a number of slots. |
1260 | * |
1261 | * Note the pipe can be reduced in capacity, but only if the current |
1262 | * occupancy doesn't exceed nr_slots; if it does, EBUSY will be |
1263 | * returned instead. |
1264 | */ |
1265 | int pipe_resize_ring(struct pipe_inode_info *pipe, unsigned int nr_slots) |
1266 | { |
1267 | struct pipe_buffer *bufs; |
1268 | unsigned int head, tail, mask, n; |
1269 | |
1270 | bufs = kcalloc(n: nr_slots, size: sizeof(*bufs), |
1271 | GFP_KERNEL_ACCOUNT | __GFP_NOWARN); |
1272 | if (unlikely(!bufs)) |
1273 | return -ENOMEM; |
1274 | |
1275 | spin_lock_irq(lock: &pipe->rd_wait.lock); |
1276 | mask = pipe->ring_size - 1; |
1277 | head = pipe->head; |
1278 | tail = pipe->tail; |
1279 | |
1280 | n = pipe_occupancy(head, tail); |
1281 | if (nr_slots < n) { |
1282 | spin_unlock_irq(lock: &pipe->rd_wait.lock); |
1283 | kfree(objp: bufs); |
1284 | return -EBUSY; |
1285 | } |
1286 | |
1287 | /* |
1288 | * The pipe array wraps around, so just start the new one at zero |
1289 | * and adjust the indices. |
1290 | */ |
1291 | if (n > 0) { |
1292 | unsigned int h = head & mask; |
1293 | unsigned int t = tail & mask; |
1294 | if (h > t) { |
1295 | memcpy(bufs, pipe->bufs + t, |
1296 | n * sizeof(struct pipe_buffer)); |
1297 | } else { |
1298 | unsigned int tsize = pipe->ring_size - t; |
1299 | if (h > 0) |
1300 | memcpy(bufs + tsize, pipe->bufs, |
1301 | h * sizeof(struct pipe_buffer)); |
1302 | memcpy(bufs, pipe->bufs + t, |
1303 | tsize * sizeof(struct pipe_buffer)); |
1304 | } |
1305 | } |
1306 | |
1307 | head = n; |
1308 | tail = 0; |
1309 | |
1310 | kfree(objp: pipe->bufs); |
1311 | pipe->bufs = bufs; |
1312 | pipe->ring_size = nr_slots; |
1313 | if (pipe->max_usage > nr_slots) |
1314 | pipe->max_usage = nr_slots; |
1315 | pipe->tail = tail; |
1316 | pipe->head = head; |
1317 | |
1318 | if (!pipe_has_watch_queue(pipe)) { |
1319 | pipe->max_usage = nr_slots; |
1320 | pipe->nr_accounted = nr_slots; |
1321 | } |
1322 | |
1323 | spin_unlock_irq(lock: &pipe->rd_wait.lock); |
1324 | |
1325 | /* This might have made more room for writers */ |
1326 | wake_up_interruptible(&pipe->wr_wait); |
1327 | return 0; |
1328 | } |
1329 | |
1330 | /* |
1331 | * Allocate a new array of pipe buffers and copy the info over. Returns the |
1332 | * pipe size if successful, or return -ERROR on error. |
1333 | */ |
1334 | static long pipe_set_size(struct pipe_inode_info *pipe, unsigned int arg) |
1335 | { |
1336 | unsigned long user_bufs; |
1337 | unsigned int nr_slots, size; |
1338 | long ret = 0; |
1339 | |
1340 | if (pipe_has_watch_queue(pipe)) |
1341 | return -EBUSY; |
1342 | |
1343 | size = round_pipe_size(size: arg); |
1344 | nr_slots = size >> PAGE_SHIFT; |
1345 | |
1346 | if (!nr_slots) |
1347 | return -EINVAL; |
1348 | |
1349 | /* |
1350 | * If trying to increase the pipe capacity, check that an |
1351 | * unprivileged user is not trying to exceed various limits |
1352 | * (soft limit check here, hard limit check just below). |
1353 | * Decreasing the pipe capacity is always permitted, even |
1354 | * if the user is currently over a limit. |
1355 | */ |
1356 | if (nr_slots > pipe->max_usage && |
1357 | size > pipe_max_size && !capable(CAP_SYS_RESOURCE)) |
1358 | return -EPERM; |
1359 | |
1360 | user_bufs = account_pipe_buffers(user: pipe->user, old: pipe->nr_accounted, new: nr_slots); |
1361 | |
1362 | if (nr_slots > pipe->max_usage && |
1363 | (too_many_pipe_buffers_hard(user_bufs) || |
1364 | too_many_pipe_buffers_soft(user_bufs)) && |
1365 | pipe_is_unprivileged_user()) { |
1366 | ret = -EPERM; |
1367 | goto out_revert_acct; |
1368 | } |
1369 | |
1370 | ret = pipe_resize_ring(pipe, nr_slots); |
1371 | if (ret < 0) |
1372 | goto out_revert_acct; |
1373 | |
1374 | return pipe->max_usage * PAGE_SIZE; |
1375 | |
1376 | out_revert_acct: |
1377 | (void) account_pipe_buffers(user: pipe->user, old: nr_slots, new: pipe->nr_accounted); |
1378 | return ret; |
1379 | } |
1380 | |
1381 | /* |
1382 | * Note that i_pipe and i_cdev share the same location, so checking ->i_pipe is |
1383 | * not enough to verify that this is a pipe. |
1384 | */ |
1385 | struct pipe_inode_info *get_pipe_info(struct file *file, bool for_splice) |
1386 | { |
1387 | struct pipe_inode_info *pipe = file->private_data; |
1388 | |
1389 | if (file->f_op != &pipefifo_fops || !pipe) |
1390 | return NULL; |
1391 | if (for_splice && pipe_has_watch_queue(pipe)) |
1392 | return NULL; |
1393 | return pipe; |
1394 | } |
1395 | |
1396 | long pipe_fcntl(struct file *file, unsigned int cmd, unsigned int arg) |
1397 | { |
1398 | struct pipe_inode_info *pipe; |
1399 | long ret; |
1400 | |
1401 | pipe = get_pipe_info(file, for_splice: false); |
1402 | if (!pipe) |
1403 | return -EBADF; |
1404 | |
1405 | mutex_lock(&pipe->mutex); |
1406 | |
1407 | switch (cmd) { |
1408 | case F_SETPIPE_SZ: |
1409 | ret = pipe_set_size(pipe, arg); |
1410 | break; |
1411 | case F_GETPIPE_SZ: |
1412 | ret = pipe->max_usage * PAGE_SIZE; |
1413 | break; |
1414 | default: |
1415 | ret = -EINVAL; |
1416 | break; |
1417 | } |
1418 | |
1419 | mutex_unlock(lock: &pipe->mutex); |
1420 | return ret; |
1421 | } |
1422 | |
1423 | static const struct super_operations pipefs_ops = { |
1424 | .destroy_inode = free_inode_nonrcu, |
1425 | .statfs = simple_statfs, |
1426 | }; |
1427 | |
1428 | /* |
1429 | * pipefs should _never_ be mounted by userland - too much of security hassle, |
1430 | * no real gain from having the whole whorehouse mounted. So we don't need |
1431 | * any operations on the root directory. However, we need a non-trivial |
1432 | * d_name - pipe: will go nicely and kill the special-casing in procfs. |
1433 | */ |
1434 | |
1435 | static int pipefs_init_fs_context(struct fs_context *fc) |
1436 | { |
1437 | struct pseudo_fs_context *ctx = init_pseudo(fc, PIPEFS_MAGIC); |
1438 | if (!ctx) |
1439 | return -ENOMEM; |
1440 | ctx->ops = &pipefs_ops; |
1441 | ctx->dops = &pipefs_dentry_operations; |
1442 | return 0; |
1443 | } |
1444 | |
1445 | static struct file_system_type pipe_fs_type = { |
1446 | .name = "pipefs" , |
1447 | .init_fs_context = pipefs_init_fs_context, |
1448 | .kill_sb = kill_anon_super, |
1449 | }; |
1450 | |
1451 | #ifdef CONFIG_SYSCTL |
1452 | static int do_proc_dopipe_max_size_conv(unsigned long *lvalp, |
1453 | unsigned int *valp, |
1454 | int write, void *data) |
1455 | { |
1456 | if (write) { |
1457 | unsigned int val; |
1458 | |
1459 | val = round_pipe_size(size: *lvalp); |
1460 | if (val == 0) |
1461 | return -EINVAL; |
1462 | |
1463 | *valp = val; |
1464 | } else { |
1465 | unsigned int val = *valp; |
1466 | *lvalp = (unsigned long) val; |
1467 | } |
1468 | |
1469 | return 0; |
1470 | } |
1471 | |
1472 | static int proc_dopipe_max_size(struct ctl_table *table, int write, |
1473 | void *buffer, size_t *lenp, loff_t *ppos) |
1474 | { |
1475 | return do_proc_douintvec(table, write, buffer, lenp, ppos, |
1476 | conv: do_proc_dopipe_max_size_conv, NULL); |
1477 | } |
1478 | |
1479 | static struct ctl_table fs_pipe_sysctls[] = { |
1480 | { |
1481 | .procname = "pipe-max-size" , |
1482 | .data = &pipe_max_size, |
1483 | .maxlen = sizeof(pipe_max_size), |
1484 | .mode = 0644, |
1485 | .proc_handler = proc_dopipe_max_size, |
1486 | }, |
1487 | { |
1488 | .procname = "pipe-user-pages-hard" , |
1489 | .data = &pipe_user_pages_hard, |
1490 | .maxlen = sizeof(pipe_user_pages_hard), |
1491 | .mode = 0644, |
1492 | .proc_handler = proc_doulongvec_minmax, |
1493 | }, |
1494 | { |
1495 | .procname = "pipe-user-pages-soft" , |
1496 | .data = &pipe_user_pages_soft, |
1497 | .maxlen = sizeof(pipe_user_pages_soft), |
1498 | .mode = 0644, |
1499 | .proc_handler = proc_doulongvec_minmax, |
1500 | }, |
1501 | }; |
1502 | #endif |
1503 | |
1504 | static int __init init_pipe_fs(void) |
1505 | { |
1506 | int err = register_filesystem(&pipe_fs_type); |
1507 | |
1508 | if (!err) { |
1509 | pipe_mnt = kern_mount(&pipe_fs_type); |
1510 | if (IS_ERR(ptr: pipe_mnt)) { |
1511 | err = PTR_ERR(ptr: pipe_mnt); |
1512 | unregister_filesystem(&pipe_fs_type); |
1513 | } |
1514 | } |
1515 | #ifdef CONFIG_SYSCTL |
1516 | register_sysctl_init("fs" , fs_pipe_sysctls); |
1517 | #endif |
1518 | return err; |
1519 | } |
1520 | |
1521 | fs_initcall(init_pipe_fs); |
1522 | |