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