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