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