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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
29#include <linux/uaccess.h>
30#include <asm/ioctls.h>
31
32#include "internal.h"
33
34/*
35 * The max size that a non-root user is allowed to grow the pipe. Can
36 * be set by root in /proc/sys/fs/pipe-max-size
37 */
38unsigned int pipe_max_size = 1048576;
39
40/* Maximum allocatable pages per user. Hard limit is unset by default, soft
41 * matches default values.
42 */
43unsigned long pipe_user_pages_hard;
44unsigned long pipe_user_pages_soft = PIPE_DEF_BUFFERS * INR_OPEN_CUR;
45
46/*
47 * We use head and tail indices that aren't masked off, except at the point of
48 * dereference, but rather they're allowed to wrap naturally. This means there
49 * isn't a dead spot in the buffer, but the ring has to be a power of two and
50 * <= 2^31.
51 * -- David Howells 2019-09-23.
52 *
53 * Reads with count = 0 should always return 0.
54 * -- Julian Bradfield 1999-06-07.
55 *
56 * FIFOs and Pipes now generate SIGIO for both readers and writers.
57 * -- Jeremy Elson <jelson@circlemud.org> 2001-08-16
58 *
59 * pipe_read & write cleanup
60 * -- Manfred Spraul <manfred@colorfullife.com> 2002-05-09
61 */
62
63static void pipe_lock_nested(struct pipe_inode_info *pipe, int subclass)
64{
65 if (pipe->files)
66 mutex_lock_nested(&pipe->mutex, subclass);
67}
68
69void pipe_lock(struct pipe_inode_info *pipe)
70{
71 /*
72 * pipe_lock() nests non-pipe inode locks (for writing to a file)
73 */
74 pipe_lock_nested(pipe, I_MUTEX_PARENT);
75}
76EXPORT_SYMBOL(pipe_lock);
77
78void pipe_unlock(struct pipe_inode_info *pipe)
79{
80 if (pipe->files)
81 mutex_unlock(&pipe->mutex);
82}
83EXPORT_SYMBOL(pipe_unlock);
84
85static inline void __pipe_lock(struct pipe_inode_info *pipe)
86{
87 mutex_lock_nested(&pipe->mutex, I_MUTEX_PARENT);
88}
89
90static inline void __pipe_unlock(struct pipe_inode_info *pipe)
91{
92 mutex_unlock(&pipe->mutex);
93}
94
95void pipe_double_lock(struct pipe_inode_info *pipe1,
96 struct pipe_inode_info *pipe2)
97{
98 BUG_ON(pipe1 == pipe2);
99
100 if (pipe1 < pipe2) {
101 pipe_lock_nested(pipe1, I_MUTEX_PARENT);
102 pipe_lock_nested(pipe2, I_MUTEX_CHILD);
103 } else {
104 pipe_lock_nested(pipe2, I_MUTEX_PARENT);
105 pipe_lock_nested(pipe1, I_MUTEX_CHILD);
106 }
107}
108
109static void anon_pipe_buf_release(struct pipe_inode_info *pipe,
110 struct pipe_buffer *buf)
111{
112 struct page *page = buf->page;
113
114 /*
115 * If nobody else uses this page, and we don't already have a
116 * temporary page, let's keep track of it as a one-deep
117 * allocation cache. (Otherwise just release our reference to it)
118 */
119 if (page_count(page) == 1 && !pipe->tmp_page)
120 pipe->tmp_page = page;
121 else
122 put_page(page);
123}
124
125static bool anon_pipe_buf_try_steal(struct pipe_inode_info *pipe,
126 struct pipe_buffer *buf)
127{
128 struct page *page = buf->page;
129
130 if (page_count(page) != 1)
131 return false;
132 memcg_kmem_uncharge_page(page, 0);
133 __SetPageLocked(page);
134 return true;
135}
136
137/**
138 * generic_pipe_buf_try_steal - attempt to take ownership of a &pipe_buffer
139 * @pipe: the pipe that the buffer belongs to
140 * @buf: the buffer to attempt to steal
141 *
142 * Description:
143 * This function attempts to steal the &struct page attached to
144 * @buf. If successful, this function returns 0 and returns with
145 * the page locked. The caller may then reuse the page for whatever
146 * he wishes; the typical use is insertion into a different file
147 * page cache.
148 */
149bool generic_pipe_buf_try_steal(struct pipe_inode_info *pipe,
150 struct pipe_buffer *buf)
151{
152 struct page *page = buf->page;
153
154 /*
155 * A reference of one is golden, that means that the owner of this
156 * page is the only one holding a reference to it. lock the page
157 * and return OK.
158 */
159 if (page_count(page) == 1) {
160 lock_page(page);
161 return true;
162 }
163 return false;
164}
165EXPORT_SYMBOL(generic_pipe_buf_try_steal);
166
167/**
168 * generic_pipe_buf_get - get a reference to a &struct pipe_buffer
169 * @pipe: the pipe that the buffer belongs to
170 * @buf: the buffer to get a reference to
171 *
172 * Description:
173 * This function grabs an extra reference to @buf. It's used in
174 * in the tee() system call, when we duplicate the buffers in one
175 * pipe into another.
176 */
177bool generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
178{
179 return try_get_page(buf->page);
180}
181EXPORT_SYMBOL(generic_pipe_buf_get);
182
183/**
184 * generic_pipe_buf_release - put a reference to a &struct pipe_buffer
185 * @pipe: the pipe that the buffer belongs to
186 * @buf: the buffer to put a reference to
187 *
188 * Description:
189 * This function releases a reference to @buf.
190 */
191void generic_pipe_buf_release(struct pipe_inode_info *pipe,
192 struct pipe_buffer *buf)
193{
194 put_page(buf->page);
195}
196EXPORT_SYMBOL(generic_pipe_buf_release);
197
198static const struct pipe_buf_operations anon_pipe_buf_ops = {
199 .release = anon_pipe_buf_release,
200 .try_steal = anon_pipe_buf_try_steal,
201 .get = generic_pipe_buf_get,
202};
203
204/* Done while waiting without holding the pipe lock - thus the READ_ONCE() */
205static inline bool pipe_readable(const struct pipe_inode_info *pipe)
206{
207 unsigned int head = READ_ONCE(pipe->head);
208 unsigned int tail = READ_ONCE(pipe->tail);
209 unsigned int writers = READ_ONCE(pipe->writers);
210
211 return !pipe_empty(head, tail) || !writers;
212}
213
214static ssize_t
215pipe_read(struct kiocb *iocb, struct iov_iter *to)
216{
217 size_t total_len = iov_iter_count(to);
218 struct file *filp = iocb->ki_filp;
219 struct pipe_inode_info *pipe = filp->private_data;
220 bool was_full, wake_next_reader = false;
221 ssize_t ret;
222
223 /* Null read succeeds. */
224 if (unlikely(total_len == 0))
225 return 0;
226
227 ret = 0;
228 __pipe_lock(pipe);
229
230 /*
231 * We only wake up writers if the pipe was full when we started
232 * reading in order to avoid unnecessary wakeups.
233 *
234 * But when we do wake up writers, we do so using a sync wakeup
235 * (WF_SYNC), because we want them to get going and generate more
236 * data for us.
237 */
238 was_full = pipe_full(pipe->head, pipe->tail, pipe->max_usage);
239 for (;;) {
240 unsigned int head = pipe->head;
241 unsigned int tail = pipe->tail;
242 unsigned int mask = pipe->ring_size - 1;
243
244#ifdef CONFIG_WATCH_QUEUE
245 if (pipe->note_loss) {
246 struct watch_notification n;
247
248 if (total_len < 8) {
249 if (ret == 0)
250 ret = -ENOBUFS;
251 break;
252 }
253
254 n.type = WATCH_TYPE_META;
255 n.subtype = WATCH_META_LOSS_NOTIFICATION;
256 n.info = watch_sizeof(n);
257 if (copy_to_iter(&n, sizeof(n), to) != sizeof(n)) {
258 if (ret == 0)
259 ret = -EFAULT;
260 break;
261 }
262 ret += sizeof(n);
263 total_len -= sizeof(n);
264 pipe->note_loss = false;
265 }
266#endif
267
268 if (!pipe_empty(head, tail)) {
269 struct pipe_buffer *buf = &pipe->bufs[tail & mask];
270 size_t chars = buf->len;
271 size_t written;
272 int error;
273
274 if (chars > total_len) {
275 if (buf->flags & PIPE_BUF_FLAG_WHOLE) {
276 if (ret == 0)
277 ret = -ENOBUFS;
278 break;
279 }
280 chars = total_len;
281 }
282
283 error = pipe_buf_confirm(pipe, buf);
284 if (error) {
285 if (!ret)
286 ret = error;
287 break;
288 }
289
290 written = copy_page_to_iter(buf->page, buf->offset, chars, to);
291 if (unlikely(written < chars)) {
292 if (!ret)
293 ret = -EFAULT;
294 break;
295 }
296 ret += chars;
297 buf->offset += chars;
298 buf->len -= chars;
299
300 /* Was it a packet buffer? Clean up and exit */
301 if (buf->flags & PIPE_BUF_FLAG_PACKET) {
302 total_len = chars;
303 buf->len = 0;
304 }
305
306 if (!buf->len) {
307 pipe_buf_release(pipe, buf);
308 spin_lock_irq(&pipe->rd_wait.lock);
309#ifdef CONFIG_WATCH_QUEUE
310 if (buf->flags & PIPE_BUF_FLAG_LOSS)
311 pipe->note_loss = true;
312#endif
313 tail++;
314 pipe->tail = tail;
315 spin_unlock_irq(&pipe->rd_wait.lock);
316 }
317 total_len -= chars;
318 if (!total_len)
319 break; /* common path: read succeeded */
320 if (!pipe_empty(head, tail)) /* More to do? */
321 continue;
322 }
323
324 if (!pipe->writers)
325 break;
326 if (ret)
327 break;
328 if (filp->f_flags & O_NONBLOCK) {
329 ret = -EAGAIN;
330 break;
331 }
332 __pipe_unlock(pipe);
333
334 /*
335 * We only get here if we didn't actually read anything.
336 *
337 * However, we could have seen (and removed) a zero-sized
338 * pipe buffer, and might have made space in the buffers
339 * that way.
340 *
341 * You can't make zero-sized pipe buffers by doing an empty
342 * write (not even in packet mode), but they can happen if
343 * the writer gets an EFAULT when trying to fill a buffer
344 * that already got allocated and inserted in the buffer
345 * array.
346 *
347 * So we still need to wake up any pending writers in the
348 * _very_ unlikely case that the pipe was full, but we got
349 * no data.
350 */
351 if (unlikely(was_full)) {
352 wake_up_interruptible_sync_poll(&pipe->wr_wait, EPOLLOUT | EPOLLWRNORM);
353 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
354 }
355
356 /*
357 * But because we didn't read anything, at this point we can
358 * just return directly with -ERESTARTSYS if we're interrupted,
359 * since we've done any required wakeups and there's no need
360 * to mark anything accessed. And we've dropped the lock.
361 */
362 if (wait_event_interruptible_exclusive(pipe->rd_wait, pipe_readable(pipe)) < 0)
363 return -ERESTARTSYS;
364
365 __pipe_lock(pipe);
366 was_full = pipe_full(pipe->head, pipe->tail, pipe->max_usage);
367 wake_next_reader = true;
368 }
369 if (pipe_empty(pipe->head, pipe->tail))
370 wake_next_reader = false;
371 __pipe_unlock(pipe);
372
373 if (was_full) {
374 wake_up_interruptible_sync_poll(&pipe->wr_wait, EPOLLOUT | EPOLLWRNORM);
375 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
376 }
377 if (wake_next_reader)
378 wake_up_interruptible_sync_poll(&pipe->rd_wait, EPOLLIN | EPOLLRDNORM);
379 if (ret > 0)
380 file_accessed(filp);
381 return ret;
382}
383
384static inline int is_packetized(struct file *file)
385{
386 return (file->f_flags & O_DIRECT) != 0;
387}
388
389/* Done while waiting without holding the pipe lock - thus the READ_ONCE() */
390static inline bool pipe_writable(const struct pipe_inode_info *pipe)
391{
392 unsigned int head = READ_ONCE(pipe->head);
393 unsigned int tail = READ_ONCE(pipe->tail);
394 unsigned int max_usage = READ_ONCE(pipe->max_usage);
395
396 return !pipe_full(head, tail, max_usage) ||
397 !READ_ONCE(pipe->readers);
398}
399
400static ssize_t
401pipe_write(struct kiocb *iocb, struct iov_iter *from)
402{
403 struct file *filp = iocb->ki_filp;
404 struct pipe_inode_info *pipe = filp->private_data;
405 unsigned int head;
406 ssize_t ret = 0;
407 size_t total_len = iov_iter_count(from);
408 ssize_t chars;
409 bool was_empty = false;
410 bool wake_next_writer = false;
411
412 /* Null write succeeds. */
413 if (unlikely(total_len == 0))
414 return 0;
415
416 __pipe_lock(pipe);
417
418 if (!pipe->readers) {
419 send_sig(SIGPIPE, current, 0);
420 ret = -EPIPE;
421 goto out;
422 }
423
424#ifdef CONFIG_WATCH_QUEUE
425 if (pipe->watch_queue) {
426 ret = -EXDEV;
427 goto out;
428 }
429#endif
430
431 /*
432 * Only wake up if the pipe started out empty, since
433 * otherwise there should be no readers waiting.
434 *
435 * If it wasn't empty we try to merge new data into
436 * the last buffer.
437 *
438 * That naturally merges small writes, but it also
439 * page-aligs the rest of the writes for large writes
440 * spanning multiple pages.
441 */
442 head = pipe->head;
443 was_empty = pipe_empty(head, pipe->tail);
444 chars = total_len & (PAGE_SIZE-1);
445 if (chars && !was_empty) {
446 unsigned int mask = pipe->ring_size - 1;
447 struct pipe_buffer *buf = &pipe->bufs[(head - 1) & mask];
448 int offset = buf->offset + buf->len;
449
450 if ((buf->flags & PIPE_BUF_FLAG_CAN_MERGE) &&
451 offset + chars <= PAGE_SIZE) {
452 ret = pipe_buf_confirm(pipe, buf);
453 if (ret)
454 goto out;
455
456 ret = copy_page_from_iter(buf->page, offset, chars, from);
457 if (unlikely(ret < chars)) {
458 ret = -EFAULT;
459 goto out;
460 }
461
462 buf->len += ret;
463 if (!iov_iter_count(from))
464 goto out;
465 }
466 }
467
468 for (;;) {
469 if (!pipe->readers) {
470 send_sig(SIGPIPE, current, 0);
471 if (!ret)
472 ret = -EPIPE;
473 break;
474 }
475
476 head = pipe->head;
477 if (!pipe_full(head, pipe->tail, pipe->max_usage)) {
478 unsigned int mask = pipe->ring_size - 1;
479 struct pipe_buffer *buf = &pipe->bufs[head & mask];
480 struct page *page = pipe->tmp_page;
481 int copied;
482
483 if (!page) {
484 page = alloc_page(GFP_HIGHUSER | __GFP_ACCOUNT);
485 if (unlikely(!page)) {
486 ret = ret ? : -ENOMEM;
487 break;
488 }
489 pipe->tmp_page = page;
490 }
491
492 /* Allocate a slot in the ring in advance and attach an
493 * empty buffer. If we fault or otherwise fail to use
494 * it, either the reader will consume it or it'll still
495 * be there for the next write.
496 */
497 spin_lock_irq(&pipe->rd_wait.lock);
498
499 head = pipe->head;
500 if (pipe_full(head, pipe->tail, pipe->max_usage)) {
501 spin_unlock_irq(&pipe->rd_wait.lock);
502 continue;
503 }
504
505 pipe->head = head + 1;
506 spin_unlock_irq(&pipe->rd_wait.lock);
507
508 /* Insert it into the buffer array */
509 buf = &pipe->bufs[head & mask];
510 buf->page = page;
511 buf->ops = &anon_pipe_buf_ops;
512 buf->offset = 0;
513 buf->len = 0;
514 if (is_packetized(filp))
515 buf->flags = PIPE_BUF_FLAG_PACKET;
516 else
517 buf->flags = PIPE_BUF_FLAG_CAN_MERGE;
518 pipe->tmp_page = NULL;
519
520 copied = copy_page_from_iter(page, 0, PAGE_SIZE, from);
521 if (unlikely(copied < PAGE_SIZE && iov_iter_count(from))) {
522 if (!ret)
523 ret = -EFAULT;
524 break;
525 }
526 ret += copied;
527 buf->offset = 0;
528 buf->len = copied;
529
530 if (!iov_iter_count(from))
531 break;
532 }
533
534 if (!pipe_full(head, pipe->tail, pipe->max_usage))
535 continue;
536
537 /* Wait for buffer space to become available. */
538 if (filp->f_flags & O_NONBLOCK) {
539 if (!ret)
540 ret = -EAGAIN;
541 break;
542 }
543 if (signal_pending(current)) {
544 if (!ret)
545 ret = -ERESTARTSYS;
546 break;
547 }
548
549 /*
550 * We're going to release the pipe lock and wait for more
551 * space. We wake up any readers if necessary, and then
552 * after waiting we need to re-check whether the pipe
553 * become empty while we dropped the lock.
554 */
555 __pipe_unlock(pipe);
556 if (was_empty) {
557 wake_up_interruptible_sync_poll(&pipe->rd_wait, EPOLLIN | EPOLLRDNORM);
558 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
559 }
560 wait_event_interruptible_exclusive(pipe->wr_wait, pipe_writable(pipe));
561 __pipe_lock(pipe);
562 was_empty = pipe_empty(pipe->head, pipe->tail);
563 wake_next_writer = true;
564 }
565out:
566 if (pipe_full(pipe->head, pipe->tail, pipe->max_usage))
567 wake_next_writer = false;
568 __pipe_unlock(pipe);
569
570 /*
571 * If we do do a wakeup event, we do a 'sync' wakeup, because we
572 * want the reader to start processing things asap, rather than
573 * leave the data pending.
574 *
575 * This is particularly important for small writes, because of
576 * how (for example) the GNU make jobserver uses small writes to
577 * wake up pending jobs
578 */
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 }
583 if (wake_next_writer)
584 wake_up_interruptible_sync_poll(&pipe->wr_wait, EPOLLOUT | EPOLLWRNORM);
585 if (ret > 0 && sb_start_write_trylock(file_inode(filp)->i_sb)) {
586 int err = file_update_time(filp);
587 if (err)
588 ret = err;
589 sb_end_write(file_inode(filp)->i_sb);
590 }
591 return ret;
592}
593
594static long pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
595{
596 struct pipe_inode_info *pipe = filp->private_data;
597 int count, head, tail, mask;
598
599 switch (cmd) {
600 case FIONREAD:
601 __pipe_lock(pipe);
602 count = 0;
603 head = pipe->head;
604 tail = pipe->tail;
605 mask = pipe->ring_size - 1;
606
607 while (tail != head) {
608 count += pipe->bufs[tail & mask].len;
609 tail++;
610 }
611 __pipe_unlock(pipe);
612
613 return put_user(count, (int __user *)arg);
614
615#ifdef CONFIG_WATCH_QUEUE
616 case IOC_WATCH_QUEUE_SET_SIZE: {
617 int ret;
618 __pipe_lock(pipe);
619 ret = watch_queue_set_size(pipe, arg);
620 __pipe_unlock(pipe);
621 return ret;
622 }
623
624 case IOC_WATCH_QUEUE_SET_FILTER:
625 return watch_queue_set_filter(
626 pipe, (struct watch_notification_filter __user *)arg);
627#endif
628
629 default:
630 return -ENOIOCTLCMD;
631 }
632}
633
634/* No kernel lock held - fine */
635static __poll_t
636pipe_poll(struct file *filp, poll_table *wait)
637{
638 __poll_t mask;
639 struct pipe_inode_info *pipe = filp->private_data;
640 unsigned int head, tail;
641
642 /*
643 * Reading pipe state only -- no need for acquiring the semaphore.
644 *
645 * But because this is racy, the code has to add the
646 * entry to the poll table _first_ ..
647 */
648 if (filp->f_mode & FMODE_READ)
649 poll_wait(filp, &pipe->rd_wait, wait);
650 if (filp->f_mode & FMODE_WRITE)
651 poll_wait(filp, &pipe->wr_wait, wait);
652
653 /*
654 * .. and only then can you do the racy tests. That way,
655 * if something changes and you got it wrong, the poll
656 * table entry will wake you up and fix it.
657 */
658 head = READ_ONCE(pipe->head);
659 tail = READ_ONCE(pipe->tail);
660
661 mask = 0;
662 if (filp->f_mode & FMODE_READ) {
663 if (!pipe_empty(head, tail))
664 mask |= EPOLLIN | EPOLLRDNORM;
665 if (!pipe->writers && filp->f_version != pipe->w_counter)
666 mask |= EPOLLHUP;
667 }
668
669 if (filp->f_mode & FMODE_WRITE) {
670 if (!pipe_full(head, tail, pipe->max_usage))
671 mask |= EPOLLOUT | EPOLLWRNORM;
672 /*
673 * Most Unices do not set EPOLLERR for FIFOs but on Linux they
674 * behave exactly like pipes for poll().
675 */
676 if (!pipe->readers)
677 mask |= EPOLLERR;
678 }
679
680 return mask;
681}
682
683static void put_pipe_info(struct inode *inode, struct pipe_inode_info *pipe)
684{
685 int kill = 0;
686
687 spin_lock(&inode->i_lock);
688 if (!--pipe->files) {
689 inode->i_pipe = NULL;
690 kill = 1;
691 }
692 spin_unlock(&inode->i_lock);
693
694 if (kill)
695 free_pipe_info(pipe);
696}
697
698static int
699pipe_release(struct inode *inode, struct file *file)
700{
701 struct pipe_inode_info *pipe = file->private_data;
702
703 __pipe_lock(pipe);
704 if (file->f_mode & FMODE_READ)
705 pipe->readers--;
706 if (file->f_mode & FMODE_WRITE)
707 pipe->writers--;
708
709 /* Was that the last reader or writer, but not the other side? */
710 if (!pipe->readers != !pipe->writers) {
711 wake_up_interruptible_all(&pipe->rd_wait);
712 wake_up_interruptible_all(&pipe->wr_wait);
713 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
714 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
715 }
716 __pipe_unlock(pipe);
717
718 put_pipe_info(inode, pipe);
719 return 0;
720}
721
722static int
723pipe_fasync(int fd, struct file *filp, int on)
724{
725 struct pipe_inode_info *pipe = filp->private_data;
726 int retval = 0;
727
728 __pipe_lock(pipe);
729 if (filp->f_mode & FMODE_READ)
730 retval = fasync_helper(fd, filp, on, &pipe->fasync_readers);
731 if ((filp->f_mode & FMODE_WRITE) && retval >= 0) {
732 retval = fasync_helper(fd, filp, on, &pipe->fasync_writers);
733 if (retval < 0 && (filp->f_mode & FMODE_READ))
734 /* this can happen only if on == T */
735 fasync_helper(-1, filp, 0, &pipe->fasync_readers);
736 }
737 __pipe_unlock(pipe);
738 return retval;
739}
740
741unsigned long account_pipe_buffers(struct user_struct *user,
742 unsigned long old, unsigned long new)
743{
744 return atomic_long_add_return(new - old, &user->pipe_bufs);
745}
746
747bool too_many_pipe_buffers_soft(unsigned long user_bufs)
748{
749 unsigned long soft_limit = READ_ONCE(pipe_user_pages_soft);
750
751 return soft_limit && user_bufs > soft_limit;
752}
753
754bool too_many_pipe_buffers_hard(unsigned long user_bufs)
755{
756 unsigned long hard_limit = READ_ONCE(pipe_user_pages_hard);
757
758 return hard_limit && user_bufs > hard_limit;
759}
760
761bool pipe_is_unprivileged_user(void)
762{
763 return !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN);
764}
765
766struct pipe_inode_info *alloc_pipe_info(void)
767{
768 struct pipe_inode_info *pipe;
769 unsigned long pipe_bufs = PIPE_DEF_BUFFERS;
770 struct user_struct *user = get_current_user();
771 unsigned long user_bufs;
772 unsigned int max_size = READ_ONCE(pipe_max_size);
773
774 pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL_ACCOUNT);
775 if (pipe == NULL)
776 goto out_free_uid;
777
778 if (pipe_bufs * PAGE_SIZE > max_size && !capable(CAP_SYS_RESOURCE))
779 pipe_bufs = max_size >> PAGE_SHIFT;
780
781 user_bufs = account_pipe_buffers(user, 0, pipe_bufs);
782
783 if (too_many_pipe_buffers_soft(user_bufs) && pipe_is_unprivileged_user()) {
784 user_bufs = account_pipe_buffers(user, pipe_bufs, 1);
785 pipe_bufs = 1;
786 }
787
788 if (too_many_pipe_buffers_hard(user_bufs) && pipe_is_unprivileged_user())
789 goto out_revert_acct;
790
791 pipe->bufs = kcalloc(pipe_bufs, sizeof(struct pipe_buffer),
792 GFP_KERNEL_ACCOUNT);
793
794 if (pipe->bufs) {
795 init_waitqueue_head(&pipe->rd_wait);
796 init_waitqueue_head(&pipe->wr_wait);
797 pipe->r_counter = pipe->w_counter = 1;
798 pipe->max_usage = pipe_bufs;
799 pipe->ring_size = pipe_bufs;
800 pipe->nr_accounted = pipe_bufs;
801 pipe->user = user;
802 mutex_init(&pipe->mutex);
803 return pipe;
804 }
805
806out_revert_acct:
807 (void) account_pipe_buffers(user, pipe_bufs, 0);
808 kfree(pipe);
809out_free_uid:
810 free_uid(user);
811 return NULL;
812}
813
814void free_pipe_info(struct pipe_inode_info *pipe)
815{
816 int i;
817
818#ifdef CONFIG_WATCH_QUEUE
819 if (pipe->watch_queue) {
820 watch_queue_clear(pipe->watch_queue);
821 put_watch_queue(pipe->watch_queue);
822 }
823#endif
824
825 (void) account_pipe_buffers(pipe->user, pipe->nr_accounted, 0);
826 free_uid(pipe->user);
827 for (i = 0; i < pipe->ring_size; i++) {
828 struct pipe_buffer *buf = pipe->bufs + i;
829 if (buf->ops)
830 pipe_buf_release(pipe, buf);
831 }
832 if (pipe->tmp_page)
833 __free_page(pipe->tmp_page);
834 kfree(pipe->bufs);
835 kfree(pipe);
836}
837
838static struct vfsmount *pipe_mnt __read_mostly;
839
840/*
841 * pipefs_dname() is called from d_path().
842 */
843static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen)
844{
845 return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]",
846 d_inode(dentry)->i_ino);
847}
848
849static const struct dentry_operations pipefs_dentry_operations = {
850 .d_dname = pipefs_dname,
851};
852
853static struct inode * get_pipe_inode(void)
854{
855 struct inode *inode = new_inode_pseudo(pipe_mnt->mnt_sb);
856 struct pipe_inode_info *pipe;
857
858 if (!inode)
859 goto fail_inode;
860
861 inode->i_ino = get_next_ino();
862
863 pipe = alloc_pipe_info();
864 if (!pipe)
865 goto fail_iput;
866
867 inode->i_pipe = pipe;
868 pipe->files = 2;
869 pipe->readers = pipe->writers = 1;
870 inode->i_fop = &pipefifo_fops;
871
872 /*
873 * Mark the inode dirty from the very beginning,
874 * that way it will never be moved to the dirty
875 * list because "mark_inode_dirty()" will think
876 * that it already _is_ on the dirty list.
877 */
878 inode->i_state = I_DIRTY;
879 inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR;
880 inode->i_uid = current_fsuid();
881 inode->i_gid = current_fsgid();
882 inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
883
884 return inode;
885
886fail_iput:
887 iput(inode);
888
889fail_inode:
890 return NULL;
891}
892
893int create_pipe_files(struct file **res, int flags)
894{
895 struct inode *inode = get_pipe_inode();
896 struct file *f;
897 int error;
898
899 if (!inode)
900 return -ENFILE;
901
902 if (flags & O_NOTIFICATION_PIPE) {
903 error = watch_queue_init(inode->i_pipe);
904 if (error) {
905 free_pipe_info(inode->i_pipe);
906 iput(inode);
907 return error;
908 }
909 }
910
911 f = alloc_file_pseudo(inode, pipe_mnt, "",
912 O_WRONLY | (flags & (O_NONBLOCK | O_DIRECT)),
913 &pipefifo_fops);
914 if (IS_ERR(f)) {
915 free_pipe_info(inode->i_pipe);
916 iput(inode);
917 return PTR_ERR(f);
918 }
919
920 f->private_data = inode->i_pipe;
921
922 res[0] = alloc_file_clone(f, O_RDONLY | (flags & O_NONBLOCK),
923 &pipefifo_fops);
924 if (IS_ERR(res[0])) {
925 put_pipe_info(inode, inode->i_pipe);
926 fput(f);
927 return PTR_ERR(res[0]);
928 }
929 res[0]->private_data = inode->i_pipe;
930 res[1] = f;
931 stream_open(inode, res[0]);
932 stream_open(inode, res[1]);
933 return 0;
934}
935
936static int __do_pipe_flags(int *fd, struct file **files, int flags)
937{
938 int error;
939 int fdw, fdr;
940
941 if (flags & ~(O_CLOEXEC | O_NONBLOCK | O_DIRECT | O_NOTIFICATION_PIPE))
942 return -EINVAL;
943
944 error = create_pipe_files(files, flags);
945 if (error)
946 return error;
947
948 error = get_unused_fd_flags(flags);
949 if (error < 0)
950 goto err_read_pipe;
951 fdr = error;
952
953 error = get_unused_fd_flags(flags);
954 if (error < 0)
955 goto err_fdr;
956 fdw = error;
957
958 audit_fd_pair(fdr, fdw);
959 fd[0] = fdr;
960 fd[1] = fdw;
961 return 0;
962
963 err_fdr:
964 put_unused_fd(fdr);
965 err_read_pipe:
966 fput(files[0]);
967 fput(files[1]);
968 return error;
969}
970
971int do_pipe_flags(int *fd, int flags)
972{
973 struct file *files[2];
974 int error = __do_pipe_flags(fd, files, flags);
975 if (!error) {
976 fd_install(fd[0], files[0]);
977 fd_install(fd[1], files[1]);
978 }
979 return error;
980}
981
982/*
983 * sys_pipe() is the normal C calling standard for creating
984 * a pipe. It's not the way Unix traditionally does this, though.
985 */
986static int do_pipe2(int __user *fildes, int flags)
987{
988 struct file *files[2];
989 int fd[2];
990 int error;
991
992 error = __do_pipe_flags(fd, files, flags);
993 if (!error) {
994 if (unlikely(copy_to_user(fildes, fd, sizeof(fd)))) {
995 fput(files[0]);
996 fput(files[1]);
997 put_unused_fd(fd[0]);
998 put_unused_fd(fd[1]);
999 error = -EFAULT;
1000 } else {
1001 fd_install(fd[0], files[0]);
1002 fd_install(fd[1], files[1]);
1003 }
1004 }
1005 return error;
1006}
1007
1008SYSCALL_DEFINE2(pipe2, int __user *, fildes, int, flags)
1009{
1010 return do_pipe2(fildes, flags);
1011}
1012
1013SYSCALL_DEFINE1(pipe, int __user *, fildes)
1014{
1015 return do_pipe2(fildes, 0);
1016}
1017
1018/*
1019 * This is the stupid "wait for pipe to be readable or writable"
1020 * model.
1021 *
1022 * See pipe_read/write() for the proper kind of exclusive wait,
1023 * but that requires that we wake up any other readers/writers
1024 * if we then do not end up reading everything (ie the whole
1025 * "wake_next_reader/writer" logic in pipe_read/write()).
1026 */
1027void pipe_wait_readable(struct pipe_inode_info *pipe)
1028{
1029 pipe_unlock(pipe);
1030 wait_event_interruptible(pipe->rd_wait, pipe_readable(pipe));
1031 pipe_lock(pipe);
1032}
1033
1034void pipe_wait_writable(struct pipe_inode_info *pipe)
1035{
1036 pipe_unlock(pipe);
1037 wait_event_interruptible(pipe->wr_wait, pipe_writable(pipe));
1038 pipe_lock(pipe);
1039}
1040
1041/*
1042 * This depends on both the wait (here) and the wakeup (wake_up_partner)
1043 * holding the pipe lock, so "*cnt" is stable and we know a wakeup cannot
1044 * race with the count check and waitqueue prep.
1045 *
1046 * Normally in order to avoid races, you'd do the prepare_to_wait() first,
1047 * then check the condition you're waiting for, and only then sleep. But
1048 * because of the pipe lock, we can check the condition before being on
1049 * the wait queue.
1050 *
1051 * We use the 'rd_wait' waitqueue for pipe partner waiting.
1052 */
1053static int wait_for_partner(struct pipe_inode_info *pipe, unsigned int *cnt)
1054{
1055 DEFINE_WAIT(rdwait);
1056 int cur = *cnt;
1057
1058 while (cur == *cnt) {
1059 prepare_to_wait(&pipe->rd_wait, &rdwait, TASK_INTERRUPTIBLE);
1060 pipe_unlock(pipe);
1061 schedule();
1062 finish_wait(&pipe->rd_wait, &rdwait);
1063 pipe_lock(pipe);
1064 if (signal_pending(current))
1065 break;
1066 }
1067 return cur == *cnt ? -ERESTARTSYS : 0;
1068}
1069
1070static void wake_up_partner(struct pipe_inode_info *pipe)
1071{
1072 wake_up_interruptible_all(&pipe->rd_wait);
1073}
1074
1075static int fifo_open(struct inode *inode, struct file *filp)
1076{
1077 struct pipe_inode_info *pipe;
1078 bool is_pipe = inode->i_sb->s_magic == PIPEFS_MAGIC;
1079 int ret;
1080
1081 filp->f_version = 0;
1082
1083 spin_lock(&inode->i_lock);
1084 if (inode->i_pipe) {
1085 pipe = inode->i_pipe;
1086 pipe->files++;
1087 spin_unlock(&inode->i_lock);
1088 } else {
1089 spin_unlock(&inode->i_lock);
1090 pipe = alloc_pipe_info();
1091 if (!pipe)
1092 return -ENOMEM;
1093 pipe->files = 1;
1094 spin_lock(&inode->i_lock);
1095 if (unlikely(inode->i_pipe)) {
1096 inode->i_pipe->files++;
1097 spin_unlock(&inode->i_lock);
1098 free_pipe_info(pipe);
1099 pipe = inode->i_pipe;
1100 } else {
1101 inode->i_pipe = pipe;
1102 spin_unlock(&inode->i_lock);
1103 }
1104 }
1105 filp->private_data = pipe;
1106 /* OK, we have a pipe and it's pinned down */
1107
1108 __pipe_lock(pipe);
1109
1110 /* We can only do regular read/write on fifos */
1111 stream_open(inode, filp);
1112
1113 switch (filp->f_mode & (FMODE_READ | FMODE_WRITE)) {
1114 case FMODE_READ:
1115 /*
1116 * O_RDONLY
1117 * POSIX.1 says that O_NONBLOCK means return with the FIFO
1118 * opened, even when there is no process writing the FIFO.
1119 */
1120 pipe->r_counter++;
1121 if (pipe->readers++ == 0)
1122 wake_up_partner(pipe);
1123
1124 if (!is_pipe && !pipe->writers) {
1125 if ((filp->f_flags & O_NONBLOCK)) {
1126 /* suppress EPOLLHUP until we have
1127 * seen a writer */
1128 filp->f_version = pipe->w_counter;
1129 } else {
1130 if (wait_for_partner(pipe, &pipe->w_counter))
1131 goto err_rd;
1132 }
1133 }
1134 break;
1135
1136 case FMODE_WRITE:
1137 /*
1138 * O_WRONLY
1139 * POSIX.1 says that O_NONBLOCK means return -1 with
1140 * errno=ENXIO when there is no process reading the FIFO.
1141 */
1142 ret = -ENXIO;
1143 if (!is_pipe && (filp->f_flags & O_NONBLOCK) && !pipe->readers)
1144 goto err;
1145
1146 pipe->w_counter++;
1147 if (!pipe->writers++)
1148 wake_up_partner(pipe);
1149
1150 if (!is_pipe && !pipe->readers) {
1151 if (wait_for_partner(pipe, &pipe->r_counter))
1152 goto err_wr;
1153 }
1154 break;
1155
1156 case FMODE_READ | FMODE_WRITE:
1157 /*
1158 * O_RDWR
1159 * POSIX.1 leaves this case "undefined" when O_NONBLOCK is set.
1160 * This implementation will NEVER block on a O_RDWR open, since
1161 * the process can at least talk to itself.
1162 */
1163
1164 pipe->readers++;
1165 pipe->writers++;
1166 pipe->r_counter++;
1167 pipe->w_counter++;
1168 if (pipe->readers == 1 || pipe->writers == 1)
1169 wake_up_partner(pipe);
1170 break;
1171
1172 default:
1173 ret = -EINVAL;
1174 goto err;
1175 }
1176
1177 /* Ok! */
1178 __pipe_unlock(pipe);
1179 return 0;
1180
1181err_rd:
1182 if (!--pipe->readers)
1183 wake_up_interruptible(&pipe->wr_wait);
1184 ret = -ERESTARTSYS;
1185 goto err;
1186
1187err_wr:
1188 if (!--pipe->writers)
1189 wake_up_interruptible_all(&pipe->rd_wait);
1190 ret = -ERESTARTSYS;
1191 goto err;
1192
1193err:
1194 __pipe_unlock(pipe);
1195
1196 put_pipe_info(inode, pipe);
1197 return ret;
1198}
1199
1200const struct file_operations pipefifo_fops = {
1201 .open = fifo_open,
1202 .llseek = no_llseek,
1203 .read_iter = pipe_read,
1204 .write_iter = pipe_write,
1205 .poll = pipe_poll,
1206 .unlocked_ioctl = pipe_ioctl,
1207 .release = pipe_release,
1208 .fasync = pipe_fasync,
1209};
1210
1211/*
1212 * Currently we rely on the pipe array holding a power-of-2 number
1213 * of pages. Returns 0 on error.
1214 */
1215unsigned int round_pipe_size(unsigned long size)
1216{
1217 if (size > (1U << 31))
1218 return 0;
1219
1220 /* Minimum pipe size, as required by POSIX */
1221 if (size < PAGE_SIZE)
1222 return PAGE_SIZE;
1223
1224 return roundup_pow_of_two(size);
1225}
1226
1227/*
1228 * Resize the pipe ring to a number of slots.
1229 */
1230int pipe_resize_ring(struct pipe_inode_info *pipe, unsigned int nr_slots)
1231{
1232 struct pipe_buffer *bufs;
1233 unsigned int head, tail, mask, n;
1234
1235 /*
1236 * We can shrink the pipe, if arg is greater than the ring occupancy.
1237 * Since we don't expect a lot of shrink+grow operations, just free and
1238 * allocate again like we would do for growing. If the pipe currently
1239 * contains more buffers than arg, then return busy.
1240 */
1241 mask = pipe->ring_size - 1;
1242 head = pipe->head;
1243 tail = pipe->tail;
1244 n = pipe_occupancy(pipe->head, pipe->tail);
1245 if (nr_slots < n)
1246 return -EBUSY;
1247
1248 bufs = kcalloc(nr_slots, sizeof(*bufs),
1249 GFP_KERNEL_ACCOUNT | __GFP_NOWARN);
1250 if (unlikely(!bufs))
1251 return -ENOMEM;
1252
1253 /*
1254 * The pipe array wraps around, so just start the new one at zero
1255 * and adjust the indices.
1256 */
1257 if (n > 0) {
1258 unsigned int h = head & mask;
1259 unsigned int t = tail & mask;
1260 if (h > t) {
1261 memcpy(bufs, pipe->bufs + t,
1262 n * sizeof(struct pipe_buffer));
1263 } else {
1264 unsigned int tsize = pipe->ring_size - t;
1265 if (h > 0)
1266 memcpy(bufs + tsize, pipe->bufs,
1267 h * sizeof(struct pipe_buffer));
1268 memcpy(bufs, pipe->bufs + t,
1269 tsize * sizeof(struct pipe_buffer));
1270 }
1271 }
1272
1273 head = n;
1274 tail = 0;
1275
1276 kfree(pipe->bufs);
1277 pipe->bufs = bufs;
1278 pipe->ring_size = nr_slots;
1279 if (pipe->max_usage > nr_slots)
1280 pipe->max_usage = nr_slots;
1281 pipe->tail = tail;
1282 pipe->head = head;
1283
1284 /* This might have made more room for writers */
1285 wake_up_interruptible(&pipe->wr_wait);
1286 return 0;
1287}
1288
1289/*
1290 * Allocate a new array of pipe buffers and copy the info over. Returns the
1291 * pipe size if successful, or return -ERROR on error.
1292 */
1293static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long arg)
1294{
1295 unsigned long user_bufs;
1296 unsigned int nr_slots, size;
1297 long ret = 0;
1298
1299#ifdef CONFIG_WATCH_QUEUE
1300 if (pipe->watch_queue)
1301 return -EBUSY;
1302#endif
1303
1304 size = round_pipe_size(arg);
1305 nr_slots = size >> PAGE_SHIFT;
1306
1307 if (!nr_slots)
1308 return -EINVAL;
1309
1310 /*
1311 * If trying to increase the pipe capacity, check that an
1312 * unprivileged user is not trying to exceed various limits
1313 * (soft limit check here, hard limit check just below).
1314 * Decreasing the pipe capacity is always permitted, even
1315 * if the user is currently over a limit.
1316 */
1317 if (nr_slots > pipe->max_usage &&
1318 size > pipe_max_size && !capable(CAP_SYS_RESOURCE))
1319 return -EPERM;
1320
1321 user_bufs = account_pipe_buffers(pipe->user, pipe->nr_accounted, nr_slots);
1322
1323 if (nr_slots > pipe->max_usage &&
1324 (too_many_pipe_buffers_hard(user_bufs) ||
1325 too_many_pipe_buffers_soft(user_bufs)) &&
1326 pipe_is_unprivileged_user()) {
1327 ret = -EPERM;
1328 goto out_revert_acct;
1329 }
1330
1331 ret = pipe_resize_ring(pipe, nr_slots);
1332 if (ret < 0)
1333 goto out_revert_acct;
1334
1335 pipe->max_usage = nr_slots;
1336 pipe->nr_accounted = nr_slots;
1337 return pipe->max_usage * PAGE_SIZE;
1338
1339out_revert_acct:
1340 (void) account_pipe_buffers(pipe->user, nr_slots, pipe->nr_accounted);
1341 return ret;
1342}
1343
1344/*
1345 * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same
1346 * location, so checking ->i_pipe is not enough to verify that this is a
1347 * pipe.
1348 */
1349struct pipe_inode_info *get_pipe_info(struct file *file, bool for_splice)
1350{
1351 struct pipe_inode_info *pipe = file->private_data;
1352
1353 if (file->f_op != &pipefifo_fops || !pipe)
1354 return NULL;
1355#ifdef CONFIG_WATCH_QUEUE
1356 if (for_splice && pipe->watch_queue)
1357 return NULL;
1358#endif
1359 return pipe;
1360}
1361
1362long pipe_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
1363{
1364 struct pipe_inode_info *pipe;
1365 long ret;
1366
1367 pipe = get_pipe_info(file, false);
1368 if (!pipe)
1369 return -EBADF;
1370
1371 __pipe_lock(pipe);
1372
1373 switch (cmd) {
1374 case F_SETPIPE_SZ:
1375 ret = pipe_set_size(pipe, arg);
1376 break;
1377 case F_GETPIPE_SZ:
1378 ret = pipe->max_usage * PAGE_SIZE;
1379 break;
1380 default:
1381 ret = -EINVAL;
1382 break;
1383 }
1384
1385 __pipe_unlock(pipe);
1386 return ret;
1387}
1388
1389static const struct super_operations pipefs_ops = {
1390 .destroy_inode = free_inode_nonrcu,
1391 .statfs = simple_statfs,
1392};
1393
1394/*
1395 * pipefs should _never_ be mounted by userland - too much of security hassle,
1396 * no real gain from having the whole whorehouse mounted. So we don't need
1397 * any operations on the root directory. However, we need a non-trivial
1398 * d_name - pipe: will go nicely and kill the special-casing in procfs.
1399 */
1400
1401static int pipefs_init_fs_context(struct fs_context *fc)
1402{
1403 struct pseudo_fs_context *ctx = init_pseudo(fc, PIPEFS_MAGIC);
1404 if (!ctx)
1405 return -ENOMEM;
1406 ctx->ops = &pipefs_ops;
1407 ctx->dops = &pipefs_dentry_operations;
1408 return 0;
1409}
1410
1411static struct file_system_type pipe_fs_type = {
1412 .name = "pipefs",
1413 .init_fs_context = pipefs_init_fs_context,
1414 .kill_sb = kill_anon_super,
1415};
1416
1417static int __init init_pipe_fs(void)
1418{
1419 int err = register_filesystem(&pipe_fs_type);
1420
1421 if (!err) {
1422 pipe_mnt = kern_mount(&pipe_fs_type);
1423 if (IS_ERR(pipe_mnt)) {
1424 err = PTR_ERR(pipe_mnt);
1425 unregister_filesystem(&pipe_fs_type);
1426 }
1427 }
1428 return err;
1429}
1430
1431fs_initcall(init_pipe_fs);
1/*
2 * linux/fs/pipe.c
3 *
4 * Copyright (C) 1991, 1992, 1999 Linus Torvalds
5 */
6
7#include <linux/mm.h>
8#include <linux/file.h>
9#include <linux/poll.h>
10#include <linux/slab.h>
11#include <linux/module.h>
12#include <linux/init.h>
13#include <linux/fs.h>
14#include <linux/log2.h>
15#include <linux/mount.h>
16#include <linux/magic.h>
17#include <linux/pipe_fs_i.h>
18#include <linux/uio.h>
19#include <linux/highmem.h>
20#include <linux/pagemap.h>
21#include <linux/audit.h>
22#include <linux/syscalls.h>
23#include <linux/fcntl.h>
24#include <linux/aio.h>
25
26#include <asm/uaccess.h>
27#include <asm/ioctls.h>
28
29#include "internal.h"
30
31/*
32 * The max size that a non-root user is allowed to grow the pipe. Can
33 * be set by root in /proc/sys/fs/pipe-max-size
34 */
35unsigned int pipe_max_size = 1048576;
36
37/*
38 * Minimum pipe size, as required by POSIX
39 */
40unsigned int pipe_min_size = PAGE_SIZE;
41
42/*
43 * We use a start+len construction, which provides full use of the
44 * allocated memory.
45 * -- Florian Coosmann (FGC)
46 *
47 * Reads with count = 0 should always return 0.
48 * -- Julian Bradfield 1999-06-07.
49 *
50 * FIFOs and Pipes now generate SIGIO for both readers and writers.
51 * -- Jeremy Elson <jelson@circlemud.org> 2001-08-16
52 *
53 * pipe_read & write cleanup
54 * -- Manfred Spraul <manfred@colorfullife.com> 2002-05-09
55 */
56
57static void pipe_lock_nested(struct pipe_inode_info *pipe, int subclass)
58{
59 if (pipe->files)
60 mutex_lock_nested(&pipe->mutex, subclass);
61}
62
63void pipe_lock(struct pipe_inode_info *pipe)
64{
65 /*
66 * pipe_lock() nests non-pipe inode locks (for writing to a file)
67 */
68 pipe_lock_nested(pipe, I_MUTEX_PARENT);
69}
70EXPORT_SYMBOL(pipe_lock);
71
72void pipe_unlock(struct pipe_inode_info *pipe)
73{
74 if (pipe->files)
75 mutex_unlock(&pipe->mutex);
76}
77EXPORT_SYMBOL(pipe_unlock);
78
79static inline void __pipe_lock(struct pipe_inode_info *pipe)
80{
81 mutex_lock_nested(&pipe->mutex, I_MUTEX_PARENT);
82}
83
84static inline void __pipe_unlock(struct pipe_inode_info *pipe)
85{
86 mutex_unlock(&pipe->mutex);
87}
88
89void pipe_double_lock(struct pipe_inode_info *pipe1,
90 struct pipe_inode_info *pipe2)
91{
92 BUG_ON(pipe1 == pipe2);
93
94 if (pipe1 < pipe2) {
95 pipe_lock_nested(pipe1, I_MUTEX_PARENT);
96 pipe_lock_nested(pipe2, I_MUTEX_CHILD);
97 } else {
98 pipe_lock_nested(pipe2, I_MUTEX_PARENT);
99 pipe_lock_nested(pipe1, I_MUTEX_CHILD);
100 }
101}
102
103/* Drop the inode semaphore and wait for a pipe event, atomically */
104void pipe_wait(struct pipe_inode_info *pipe)
105{
106 DEFINE_WAIT(wait);
107
108 /*
109 * Pipes are system-local resources, so sleeping on them
110 * is considered a noninteractive wait:
111 */
112 prepare_to_wait(&pipe->wait, &wait, TASK_INTERRUPTIBLE);
113 pipe_unlock(pipe);
114 schedule();
115 finish_wait(&pipe->wait, &wait);
116 pipe_lock(pipe);
117}
118
119static int
120pipe_iov_copy_from_user(void *to, struct iovec *iov, unsigned long len,
121 int atomic)
122{
123 unsigned long copy;
124
125 while (len > 0) {
126 while (!iov->iov_len)
127 iov++;
128 copy = min_t(unsigned long, len, iov->iov_len);
129
130 if (atomic) {
131 if (__copy_from_user_inatomic(to, iov->iov_base, copy))
132 return -EFAULT;
133 } else {
134 if (copy_from_user(to, iov->iov_base, copy))
135 return -EFAULT;
136 }
137 to += copy;
138 len -= copy;
139 iov->iov_base += copy;
140 iov->iov_len -= copy;
141 }
142 return 0;
143}
144
145/*
146 * Pre-fault in the user memory, so we can use atomic copies.
147 */
148static void iov_fault_in_pages_read(struct iovec *iov, unsigned long len)
149{
150 while (!iov->iov_len)
151 iov++;
152
153 while (len > 0) {
154 unsigned long this_len;
155
156 this_len = min_t(unsigned long, len, iov->iov_len);
157 fault_in_pages_readable(iov->iov_base, this_len);
158 len -= this_len;
159 iov++;
160 }
161}
162
163static void anon_pipe_buf_release(struct pipe_inode_info *pipe,
164 struct pipe_buffer *buf)
165{
166 struct page *page = buf->page;
167
168 /*
169 * If nobody else uses this page, and we don't already have a
170 * temporary page, let's keep track of it as a one-deep
171 * allocation cache. (Otherwise just release our reference to it)
172 */
173 if (page_count(page) == 1 && !pipe->tmp_page)
174 pipe->tmp_page = page;
175 else
176 page_cache_release(page);
177}
178
179/**
180 * generic_pipe_buf_steal - attempt to take ownership of a &pipe_buffer
181 * @pipe: the pipe that the buffer belongs to
182 * @buf: the buffer to attempt to steal
183 *
184 * Description:
185 * This function attempts to steal the &struct page attached to
186 * @buf. If successful, this function returns 0 and returns with
187 * the page locked. The caller may then reuse the page for whatever
188 * he wishes; the typical use is insertion into a different file
189 * page cache.
190 */
191int generic_pipe_buf_steal(struct pipe_inode_info *pipe,
192 struct pipe_buffer *buf)
193{
194 struct page *page = buf->page;
195
196 /*
197 * A reference of one is golden, that means that the owner of this
198 * page is the only one holding a reference to it. lock the page
199 * and return OK.
200 */
201 if (page_count(page) == 1) {
202 lock_page(page);
203 return 0;
204 }
205
206 return 1;
207}
208EXPORT_SYMBOL(generic_pipe_buf_steal);
209
210/**
211 * generic_pipe_buf_get - get a reference to a &struct pipe_buffer
212 * @pipe: the pipe that the buffer belongs to
213 * @buf: the buffer to get a reference to
214 *
215 * Description:
216 * This function grabs an extra reference to @buf. It's used in
217 * in the tee() system call, when we duplicate the buffers in one
218 * pipe into another.
219 */
220void generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
221{
222 page_cache_get(buf->page);
223}
224EXPORT_SYMBOL(generic_pipe_buf_get);
225
226/**
227 * generic_pipe_buf_confirm - verify contents of the pipe buffer
228 * @info: the pipe that the buffer belongs to
229 * @buf: the buffer to confirm
230 *
231 * Description:
232 * This function does nothing, because the generic pipe code uses
233 * pages that are always good when inserted into the pipe.
234 */
235int generic_pipe_buf_confirm(struct pipe_inode_info *info,
236 struct pipe_buffer *buf)
237{
238 return 0;
239}
240EXPORT_SYMBOL(generic_pipe_buf_confirm);
241
242/**
243 * generic_pipe_buf_release - put a reference to a &struct pipe_buffer
244 * @pipe: the pipe that the buffer belongs to
245 * @buf: the buffer to put a reference to
246 *
247 * Description:
248 * This function releases a reference to @buf.
249 */
250void generic_pipe_buf_release(struct pipe_inode_info *pipe,
251 struct pipe_buffer *buf)
252{
253 page_cache_release(buf->page);
254}
255EXPORT_SYMBOL(generic_pipe_buf_release);
256
257static const struct pipe_buf_operations anon_pipe_buf_ops = {
258 .can_merge = 1,
259 .confirm = generic_pipe_buf_confirm,
260 .release = anon_pipe_buf_release,
261 .steal = generic_pipe_buf_steal,
262 .get = generic_pipe_buf_get,
263};
264
265static const struct pipe_buf_operations packet_pipe_buf_ops = {
266 .can_merge = 0,
267 .confirm = generic_pipe_buf_confirm,
268 .release = anon_pipe_buf_release,
269 .steal = generic_pipe_buf_steal,
270 .get = generic_pipe_buf_get,
271};
272
273static ssize_t
274pipe_read(struct kiocb *iocb, const struct iovec *_iov,
275 unsigned long nr_segs, loff_t pos)
276{
277 struct file *filp = iocb->ki_filp;
278 struct pipe_inode_info *pipe = filp->private_data;
279 int do_wakeup;
280 ssize_t ret;
281 struct iovec *iov = (struct iovec *)_iov;
282 size_t total_len;
283 struct iov_iter iter;
284
285 total_len = iov_length(iov, nr_segs);
286 /* Null read succeeds. */
287 if (unlikely(total_len == 0))
288 return 0;
289
290 iov_iter_init(&iter, iov, nr_segs, total_len, 0);
291
292 do_wakeup = 0;
293 ret = 0;
294 __pipe_lock(pipe);
295 for (;;) {
296 int bufs = pipe->nrbufs;
297 if (bufs) {
298 int curbuf = pipe->curbuf;
299 struct pipe_buffer *buf = pipe->bufs + curbuf;
300 const struct pipe_buf_operations *ops = buf->ops;
301 size_t chars = buf->len;
302 size_t written;
303 int error;
304
305 if (chars > total_len)
306 chars = total_len;
307
308 error = ops->confirm(pipe, buf);
309 if (error) {
310 if (!ret)
311 ret = error;
312 break;
313 }
314
315 written = copy_page_to_iter(buf->page, buf->offset, chars, &iter);
316 if (unlikely(written < chars)) {
317 if (!ret)
318 ret = -EFAULT;
319 break;
320 }
321 ret += chars;
322 buf->offset += chars;
323 buf->len -= chars;
324
325 /* Was it a packet buffer? Clean up and exit */
326 if (buf->flags & PIPE_BUF_FLAG_PACKET) {
327 total_len = chars;
328 buf->len = 0;
329 }
330
331 if (!buf->len) {
332 buf->ops = NULL;
333 ops->release(pipe, buf);
334 curbuf = (curbuf + 1) & (pipe->buffers - 1);
335 pipe->curbuf = curbuf;
336 pipe->nrbufs = --bufs;
337 do_wakeup = 1;
338 }
339 total_len -= chars;
340 if (!total_len)
341 break; /* common path: read succeeded */
342 }
343 if (bufs) /* More to do? */
344 continue;
345 if (!pipe->writers)
346 break;
347 if (!pipe->waiting_writers) {
348 /* syscall merging: Usually we must not sleep
349 * if O_NONBLOCK is set, or if we got some data.
350 * But if a writer sleeps in kernel space, then
351 * we can wait for that data without violating POSIX.
352 */
353 if (ret)
354 break;
355 if (filp->f_flags & O_NONBLOCK) {
356 ret = -EAGAIN;
357 break;
358 }
359 }
360 if (signal_pending(current)) {
361 if (!ret)
362 ret = -ERESTARTSYS;
363 break;
364 }
365 if (do_wakeup) {
366 wake_up_interruptible_sync_poll(&pipe->wait, POLLOUT | POLLWRNORM);
367 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
368 }
369 pipe_wait(pipe);
370 }
371 __pipe_unlock(pipe);
372
373 /* Signal writers asynchronously that there is more room. */
374 if (do_wakeup) {
375 wake_up_interruptible_sync_poll(&pipe->wait, POLLOUT | POLLWRNORM);
376 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
377 }
378 if (ret > 0)
379 file_accessed(filp);
380 return ret;
381}
382
383static inline int is_packetized(struct file *file)
384{
385 return (file->f_flags & O_DIRECT) != 0;
386}
387
388static ssize_t
389pipe_write(struct kiocb *iocb, const struct iovec *_iov,
390 unsigned long nr_segs, loff_t ppos)
391{
392 struct file *filp = iocb->ki_filp;
393 struct pipe_inode_info *pipe = filp->private_data;
394 ssize_t ret;
395 int do_wakeup;
396 struct iovec *iov = (struct iovec *)_iov;
397 size_t total_len;
398 ssize_t chars;
399
400 total_len = iov_length(iov, nr_segs);
401 /* Null write succeeds. */
402 if (unlikely(total_len == 0))
403 return 0;
404
405 do_wakeup = 0;
406 ret = 0;
407 __pipe_lock(pipe);
408
409 if (!pipe->readers) {
410 send_sig(SIGPIPE, current, 0);
411 ret = -EPIPE;
412 goto out;
413 }
414
415 /* We try to merge small writes */
416 chars = total_len & (PAGE_SIZE-1); /* size of the last buffer */
417 if (pipe->nrbufs && chars != 0) {
418 int lastbuf = (pipe->curbuf + pipe->nrbufs - 1) &
419 (pipe->buffers - 1);
420 struct pipe_buffer *buf = pipe->bufs + lastbuf;
421 const struct pipe_buf_operations *ops = buf->ops;
422 int offset = buf->offset + buf->len;
423
424 if (ops->can_merge && offset + chars <= PAGE_SIZE) {
425 int error, atomic = 1;
426 void *addr;
427
428 error = ops->confirm(pipe, buf);
429 if (error)
430 goto out;
431
432 iov_fault_in_pages_read(iov, chars);
433redo1:
434 if (atomic)
435 addr = kmap_atomic(buf->page);
436 else
437 addr = kmap(buf->page);
438 error = pipe_iov_copy_from_user(offset + addr, iov,
439 chars, atomic);
440 if (atomic)
441 kunmap_atomic(addr);
442 else
443 kunmap(buf->page);
444 ret = error;
445 do_wakeup = 1;
446 if (error) {
447 if (atomic) {
448 atomic = 0;
449 goto redo1;
450 }
451 goto out;
452 }
453 buf->len += chars;
454 total_len -= chars;
455 ret = chars;
456 if (!total_len)
457 goto out;
458 }
459 }
460
461 for (;;) {
462 int bufs;
463
464 if (!pipe->readers) {
465 send_sig(SIGPIPE, current, 0);
466 if (!ret)
467 ret = -EPIPE;
468 break;
469 }
470 bufs = pipe->nrbufs;
471 if (bufs < pipe->buffers) {
472 int newbuf = (pipe->curbuf + bufs) & (pipe->buffers-1);
473 struct pipe_buffer *buf = pipe->bufs + newbuf;
474 struct page *page = pipe->tmp_page;
475 char *src;
476 int error, atomic = 1;
477
478 if (!page) {
479 page = alloc_page(GFP_HIGHUSER);
480 if (unlikely(!page)) {
481 ret = ret ? : -ENOMEM;
482 break;
483 }
484 pipe->tmp_page = page;
485 }
486 /* Always wake up, even if the copy fails. Otherwise
487 * we lock up (O_NONBLOCK-)readers that sleep due to
488 * syscall merging.
489 * FIXME! Is this really true?
490 */
491 do_wakeup = 1;
492 chars = PAGE_SIZE;
493 if (chars > total_len)
494 chars = total_len;
495
496 iov_fault_in_pages_read(iov, chars);
497redo2:
498 if (atomic)
499 src = kmap_atomic(page);
500 else
501 src = kmap(page);
502
503 error = pipe_iov_copy_from_user(src, iov, chars,
504 atomic);
505 if (atomic)
506 kunmap_atomic(src);
507 else
508 kunmap(page);
509
510 if (unlikely(error)) {
511 if (atomic) {
512 atomic = 0;
513 goto redo2;
514 }
515 if (!ret)
516 ret = error;
517 break;
518 }
519 ret += chars;
520
521 /* Insert it into the buffer array */
522 buf->page = page;
523 buf->ops = &anon_pipe_buf_ops;
524 buf->offset = 0;
525 buf->len = chars;
526 buf->flags = 0;
527 if (is_packetized(filp)) {
528 buf->ops = &packet_pipe_buf_ops;
529 buf->flags = PIPE_BUF_FLAG_PACKET;
530 }
531 pipe->nrbufs = ++bufs;
532 pipe->tmp_page = NULL;
533
534 total_len -= chars;
535 if (!total_len)
536 break;
537 }
538 if (bufs < pipe->buffers)
539 continue;
540 if (filp->f_flags & O_NONBLOCK) {
541 if (!ret)
542 ret = -EAGAIN;
543 break;
544 }
545 if (signal_pending(current)) {
546 if (!ret)
547 ret = -ERESTARTSYS;
548 break;
549 }
550 if (do_wakeup) {
551 wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLRDNORM);
552 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
553 do_wakeup = 0;
554 }
555 pipe->waiting_writers++;
556 pipe_wait(pipe);
557 pipe->waiting_writers--;
558 }
559out:
560 __pipe_unlock(pipe);
561 if (do_wakeup) {
562 wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLRDNORM);
563 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
564 }
565 if (ret > 0 && sb_start_write_trylock(file_inode(filp)->i_sb)) {
566 int err = file_update_time(filp);
567 if (err)
568 ret = err;
569 sb_end_write(file_inode(filp)->i_sb);
570 }
571 return ret;
572}
573
574static long pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
575{
576 struct pipe_inode_info *pipe = filp->private_data;
577 int count, buf, nrbufs;
578
579 switch (cmd) {
580 case FIONREAD:
581 __pipe_lock(pipe);
582 count = 0;
583 buf = pipe->curbuf;
584 nrbufs = pipe->nrbufs;
585 while (--nrbufs >= 0) {
586 count += pipe->bufs[buf].len;
587 buf = (buf+1) & (pipe->buffers - 1);
588 }
589 __pipe_unlock(pipe);
590
591 return put_user(count, (int __user *)arg);
592 default:
593 return -ENOIOCTLCMD;
594 }
595}
596
597/* No kernel lock held - fine */
598static unsigned int
599pipe_poll(struct file *filp, poll_table *wait)
600{
601 unsigned int mask;
602 struct pipe_inode_info *pipe = filp->private_data;
603 int nrbufs;
604
605 poll_wait(filp, &pipe->wait, wait);
606
607 /* Reading only -- no need for acquiring the semaphore. */
608 nrbufs = pipe->nrbufs;
609 mask = 0;
610 if (filp->f_mode & FMODE_READ) {
611 mask = (nrbufs > 0) ? POLLIN | POLLRDNORM : 0;
612 if (!pipe->writers && filp->f_version != pipe->w_counter)
613 mask |= POLLHUP;
614 }
615
616 if (filp->f_mode & FMODE_WRITE) {
617 mask |= (nrbufs < pipe->buffers) ? POLLOUT | POLLWRNORM : 0;
618 /*
619 * Most Unices do not set POLLERR for FIFOs but on Linux they
620 * behave exactly like pipes for poll().
621 */
622 if (!pipe->readers)
623 mask |= POLLERR;
624 }
625
626 return mask;
627}
628
629static void put_pipe_info(struct inode *inode, struct pipe_inode_info *pipe)
630{
631 int kill = 0;
632
633 spin_lock(&inode->i_lock);
634 if (!--pipe->files) {
635 inode->i_pipe = NULL;
636 kill = 1;
637 }
638 spin_unlock(&inode->i_lock);
639
640 if (kill)
641 free_pipe_info(pipe);
642}
643
644static int
645pipe_release(struct inode *inode, struct file *file)
646{
647 struct pipe_inode_info *pipe = file->private_data;
648
649 __pipe_lock(pipe);
650 if (file->f_mode & FMODE_READ)
651 pipe->readers--;
652 if (file->f_mode & FMODE_WRITE)
653 pipe->writers--;
654
655 if (pipe->readers || pipe->writers) {
656 wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLOUT | POLLRDNORM | POLLWRNORM | POLLERR | POLLHUP);
657 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
658 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
659 }
660 __pipe_unlock(pipe);
661
662 put_pipe_info(inode, pipe);
663 return 0;
664}
665
666static int
667pipe_fasync(int fd, struct file *filp, int on)
668{
669 struct pipe_inode_info *pipe = filp->private_data;
670 int retval = 0;
671
672 __pipe_lock(pipe);
673 if (filp->f_mode & FMODE_READ)
674 retval = fasync_helper(fd, filp, on, &pipe->fasync_readers);
675 if ((filp->f_mode & FMODE_WRITE) && retval >= 0) {
676 retval = fasync_helper(fd, filp, on, &pipe->fasync_writers);
677 if (retval < 0 && (filp->f_mode & FMODE_READ))
678 /* this can happen only if on == T */
679 fasync_helper(-1, filp, 0, &pipe->fasync_readers);
680 }
681 __pipe_unlock(pipe);
682 return retval;
683}
684
685struct pipe_inode_info *alloc_pipe_info(void)
686{
687 struct pipe_inode_info *pipe;
688
689 pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL);
690 if (pipe) {
691 pipe->bufs = kzalloc(sizeof(struct pipe_buffer) * PIPE_DEF_BUFFERS, GFP_KERNEL);
692 if (pipe->bufs) {
693 init_waitqueue_head(&pipe->wait);
694 pipe->r_counter = pipe->w_counter = 1;
695 pipe->buffers = PIPE_DEF_BUFFERS;
696 mutex_init(&pipe->mutex);
697 return pipe;
698 }
699 kfree(pipe);
700 }
701
702 return NULL;
703}
704
705void free_pipe_info(struct pipe_inode_info *pipe)
706{
707 int i;
708
709 for (i = 0; i < pipe->buffers; i++) {
710 struct pipe_buffer *buf = pipe->bufs + i;
711 if (buf->ops)
712 buf->ops->release(pipe, buf);
713 }
714 if (pipe->tmp_page)
715 __free_page(pipe->tmp_page);
716 kfree(pipe->bufs);
717 kfree(pipe);
718}
719
720static struct vfsmount *pipe_mnt __read_mostly;
721
722/*
723 * pipefs_dname() is called from d_path().
724 */
725static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen)
726{
727 return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]",
728 dentry->d_inode->i_ino);
729}
730
731static const struct dentry_operations pipefs_dentry_operations = {
732 .d_dname = pipefs_dname,
733};
734
735static struct inode * get_pipe_inode(void)
736{
737 struct inode *inode = new_inode_pseudo(pipe_mnt->mnt_sb);
738 struct pipe_inode_info *pipe;
739
740 if (!inode)
741 goto fail_inode;
742
743 inode->i_ino = get_next_ino();
744
745 pipe = alloc_pipe_info();
746 if (!pipe)
747 goto fail_iput;
748
749 inode->i_pipe = pipe;
750 pipe->files = 2;
751 pipe->readers = pipe->writers = 1;
752 inode->i_fop = &pipefifo_fops;
753
754 /*
755 * Mark the inode dirty from the very beginning,
756 * that way it will never be moved to the dirty
757 * list because "mark_inode_dirty()" will think
758 * that it already _is_ on the dirty list.
759 */
760 inode->i_state = I_DIRTY;
761 inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR;
762 inode->i_uid = current_fsuid();
763 inode->i_gid = current_fsgid();
764 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
765
766 return inode;
767
768fail_iput:
769 iput(inode);
770
771fail_inode:
772 return NULL;
773}
774
775int create_pipe_files(struct file **res, int flags)
776{
777 int err;
778 struct inode *inode = get_pipe_inode();
779 struct file *f;
780 struct path path;
781 static struct qstr name = { .name = "" };
782
783 if (!inode)
784 return -ENFILE;
785
786 err = -ENOMEM;
787 path.dentry = d_alloc_pseudo(pipe_mnt->mnt_sb, &name);
788 if (!path.dentry)
789 goto err_inode;
790 path.mnt = mntget(pipe_mnt);
791
792 d_instantiate(path.dentry, inode);
793
794 err = -ENFILE;
795 f = alloc_file(&path, FMODE_WRITE, &pipefifo_fops);
796 if (IS_ERR(f))
797 goto err_dentry;
798
799 f->f_flags = O_WRONLY | (flags & (O_NONBLOCK | O_DIRECT));
800 f->private_data = inode->i_pipe;
801
802 res[0] = alloc_file(&path, FMODE_READ, &pipefifo_fops);
803 if (IS_ERR(res[0]))
804 goto err_file;
805
806 path_get(&path);
807 res[0]->private_data = inode->i_pipe;
808 res[0]->f_flags = O_RDONLY | (flags & O_NONBLOCK);
809 res[1] = f;
810 return 0;
811
812err_file:
813 put_filp(f);
814err_dentry:
815 free_pipe_info(inode->i_pipe);
816 path_put(&path);
817 return err;
818
819err_inode:
820 free_pipe_info(inode->i_pipe);
821 iput(inode);
822 return err;
823}
824
825static int __do_pipe_flags(int *fd, struct file **files, int flags)
826{
827 int error;
828 int fdw, fdr;
829
830 if (flags & ~(O_CLOEXEC | O_NONBLOCK | O_DIRECT))
831 return -EINVAL;
832
833 error = create_pipe_files(files, flags);
834 if (error)
835 return error;
836
837 error = get_unused_fd_flags(flags);
838 if (error < 0)
839 goto err_read_pipe;
840 fdr = error;
841
842 error = get_unused_fd_flags(flags);
843 if (error < 0)
844 goto err_fdr;
845 fdw = error;
846
847 audit_fd_pair(fdr, fdw);
848 fd[0] = fdr;
849 fd[1] = fdw;
850 return 0;
851
852 err_fdr:
853 put_unused_fd(fdr);
854 err_read_pipe:
855 fput(files[0]);
856 fput(files[1]);
857 return error;
858}
859
860int do_pipe_flags(int *fd, int flags)
861{
862 struct file *files[2];
863 int error = __do_pipe_flags(fd, files, flags);
864 if (!error) {
865 fd_install(fd[0], files[0]);
866 fd_install(fd[1], files[1]);
867 }
868 return error;
869}
870
871/*
872 * sys_pipe() is the normal C calling standard for creating
873 * a pipe. It's not the way Unix traditionally does this, though.
874 */
875SYSCALL_DEFINE2(pipe2, int __user *, fildes, int, flags)
876{
877 struct file *files[2];
878 int fd[2];
879 int error;
880
881 error = __do_pipe_flags(fd, files, flags);
882 if (!error) {
883 if (unlikely(copy_to_user(fildes, fd, sizeof(fd)))) {
884 fput(files[0]);
885 fput(files[1]);
886 put_unused_fd(fd[0]);
887 put_unused_fd(fd[1]);
888 error = -EFAULT;
889 } else {
890 fd_install(fd[0], files[0]);
891 fd_install(fd[1], files[1]);
892 }
893 }
894 return error;
895}
896
897SYSCALL_DEFINE1(pipe, int __user *, fildes)
898{
899 return sys_pipe2(fildes, 0);
900}
901
902static int wait_for_partner(struct pipe_inode_info *pipe, unsigned int *cnt)
903{
904 int cur = *cnt;
905
906 while (cur == *cnt) {
907 pipe_wait(pipe);
908 if (signal_pending(current))
909 break;
910 }
911 return cur == *cnt ? -ERESTARTSYS : 0;
912}
913
914static void wake_up_partner(struct pipe_inode_info *pipe)
915{
916 wake_up_interruptible(&pipe->wait);
917}
918
919static int fifo_open(struct inode *inode, struct file *filp)
920{
921 struct pipe_inode_info *pipe;
922 bool is_pipe = inode->i_sb->s_magic == PIPEFS_MAGIC;
923 int ret;
924
925 filp->f_version = 0;
926
927 spin_lock(&inode->i_lock);
928 if (inode->i_pipe) {
929 pipe = inode->i_pipe;
930 pipe->files++;
931 spin_unlock(&inode->i_lock);
932 } else {
933 spin_unlock(&inode->i_lock);
934 pipe = alloc_pipe_info();
935 if (!pipe)
936 return -ENOMEM;
937 pipe->files = 1;
938 spin_lock(&inode->i_lock);
939 if (unlikely(inode->i_pipe)) {
940 inode->i_pipe->files++;
941 spin_unlock(&inode->i_lock);
942 free_pipe_info(pipe);
943 pipe = inode->i_pipe;
944 } else {
945 inode->i_pipe = pipe;
946 spin_unlock(&inode->i_lock);
947 }
948 }
949 filp->private_data = pipe;
950 /* OK, we have a pipe and it's pinned down */
951
952 __pipe_lock(pipe);
953
954 /* We can only do regular read/write on fifos */
955 filp->f_mode &= (FMODE_READ | FMODE_WRITE);
956
957 switch (filp->f_mode) {
958 case FMODE_READ:
959 /*
960 * O_RDONLY
961 * POSIX.1 says that O_NONBLOCK means return with the FIFO
962 * opened, even when there is no process writing the FIFO.
963 */
964 pipe->r_counter++;
965 if (pipe->readers++ == 0)
966 wake_up_partner(pipe);
967
968 if (!is_pipe && !pipe->writers) {
969 if ((filp->f_flags & O_NONBLOCK)) {
970 /* suppress POLLHUP until we have
971 * seen a writer */
972 filp->f_version = pipe->w_counter;
973 } else {
974 if (wait_for_partner(pipe, &pipe->w_counter))
975 goto err_rd;
976 }
977 }
978 break;
979
980 case FMODE_WRITE:
981 /*
982 * O_WRONLY
983 * POSIX.1 says that O_NONBLOCK means return -1 with
984 * errno=ENXIO when there is no process reading the FIFO.
985 */
986 ret = -ENXIO;
987 if (!is_pipe && (filp->f_flags & O_NONBLOCK) && !pipe->readers)
988 goto err;
989
990 pipe->w_counter++;
991 if (!pipe->writers++)
992 wake_up_partner(pipe);
993
994 if (!is_pipe && !pipe->readers) {
995 if (wait_for_partner(pipe, &pipe->r_counter))
996 goto err_wr;
997 }
998 break;
999
1000 case FMODE_READ | FMODE_WRITE:
1001 /*
1002 * O_RDWR
1003 * POSIX.1 leaves this case "undefined" when O_NONBLOCK is set.
1004 * This implementation will NEVER block on a O_RDWR open, since
1005 * the process can at least talk to itself.
1006 */
1007
1008 pipe->readers++;
1009 pipe->writers++;
1010 pipe->r_counter++;
1011 pipe->w_counter++;
1012 if (pipe->readers == 1 || pipe->writers == 1)
1013 wake_up_partner(pipe);
1014 break;
1015
1016 default:
1017 ret = -EINVAL;
1018 goto err;
1019 }
1020
1021 /* Ok! */
1022 __pipe_unlock(pipe);
1023 return 0;
1024
1025err_rd:
1026 if (!--pipe->readers)
1027 wake_up_interruptible(&pipe->wait);
1028 ret = -ERESTARTSYS;
1029 goto err;
1030
1031err_wr:
1032 if (!--pipe->writers)
1033 wake_up_interruptible(&pipe->wait);
1034 ret = -ERESTARTSYS;
1035 goto err;
1036
1037err:
1038 __pipe_unlock(pipe);
1039
1040 put_pipe_info(inode, pipe);
1041 return ret;
1042}
1043
1044const struct file_operations pipefifo_fops = {
1045 .open = fifo_open,
1046 .llseek = no_llseek,
1047 .read = do_sync_read,
1048 .aio_read = pipe_read,
1049 .write = do_sync_write,
1050 .aio_write = pipe_write,
1051 .poll = pipe_poll,
1052 .unlocked_ioctl = pipe_ioctl,
1053 .release = pipe_release,
1054 .fasync = pipe_fasync,
1055};
1056
1057/*
1058 * Allocate a new array of pipe buffers and copy the info over. Returns the
1059 * pipe size if successful, or return -ERROR on error.
1060 */
1061static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long nr_pages)
1062{
1063 struct pipe_buffer *bufs;
1064
1065 /*
1066 * We can shrink the pipe, if arg >= pipe->nrbufs. Since we don't
1067 * expect a lot of shrink+grow operations, just free and allocate
1068 * again like we would do for growing. If the pipe currently
1069 * contains more buffers than arg, then return busy.
1070 */
1071 if (nr_pages < pipe->nrbufs)
1072 return -EBUSY;
1073
1074 bufs = kcalloc(nr_pages, sizeof(*bufs), GFP_KERNEL | __GFP_NOWARN);
1075 if (unlikely(!bufs))
1076 return -ENOMEM;
1077
1078 /*
1079 * The pipe array wraps around, so just start the new one at zero
1080 * and adjust the indexes.
1081 */
1082 if (pipe->nrbufs) {
1083 unsigned int tail;
1084 unsigned int head;
1085
1086 tail = pipe->curbuf + pipe->nrbufs;
1087 if (tail < pipe->buffers)
1088 tail = 0;
1089 else
1090 tail &= (pipe->buffers - 1);
1091
1092 head = pipe->nrbufs - tail;
1093 if (head)
1094 memcpy(bufs, pipe->bufs + pipe->curbuf, head * sizeof(struct pipe_buffer));
1095 if (tail)
1096 memcpy(bufs + head, pipe->bufs, tail * sizeof(struct pipe_buffer));
1097 }
1098
1099 pipe->curbuf = 0;
1100 kfree(pipe->bufs);
1101 pipe->bufs = bufs;
1102 pipe->buffers = nr_pages;
1103 return nr_pages * PAGE_SIZE;
1104}
1105
1106/*
1107 * Currently we rely on the pipe array holding a power-of-2 number
1108 * of pages.
1109 */
1110static inline unsigned int round_pipe_size(unsigned int size)
1111{
1112 unsigned long nr_pages;
1113
1114 nr_pages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
1115 return roundup_pow_of_two(nr_pages) << PAGE_SHIFT;
1116}
1117
1118/*
1119 * This should work even if CONFIG_PROC_FS isn't set, as proc_dointvec_minmax
1120 * will return an error.
1121 */
1122int pipe_proc_fn(struct ctl_table *table, int write, void __user *buf,
1123 size_t *lenp, loff_t *ppos)
1124{
1125 int ret;
1126
1127 ret = proc_dointvec_minmax(table, write, buf, lenp, ppos);
1128 if (ret < 0 || !write)
1129 return ret;
1130
1131 pipe_max_size = round_pipe_size(pipe_max_size);
1132 return ret;
1133}
1134
1135/*
1136 * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same
1137 * location, so checking ->i_pipe is not enough to verify that this is a
1138 * pipe.
1139 */
1140struct pipe_inode_info *get_pipe_info(struct file *file)
1141{
1142 return file->f_op == &pipefifo_fops ? file->private_data : NULL;
1143}
1144
1145long pipe_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
1146{
1147 struct pipe_inode_info *pipe;
1148 long ret;
1149
1150 pipe = get_pipe_info(file);
1151 if (!pipe)
1152 return -EBADF;
1153
1154 __pipe_lock(pipe);
1155
1156 switch (cmd) {
1157 case F_SETPIPE_SZ: {
1158 unsigned int size, nr_pages;
1159
1160 size = round_pipe_size(arg);
1161 nr_pages = size >> PAGE_SHIFT;
1162
1163 ret = -EINVAL;
1164 if (!nr_pages)
1165 goto out;
1166
1167 if (!capable(CAP_SYS_RESOURCE) && size > pipe_max_size) {
1168 ret = -EPERM;
1169 goto out;
1170 }
1171 ret = pipe_set_size(pipe, nr_pages);
1172 break;
1173 }
1174 case F_GETPIPE_SZ:
1175 ret = pipe->buffers * PAGE_SIZE;
1176 break;
1177 default:
1178 ret = -EINVAL;
1179 break;
1180 }
1181
1182out:
1183 __pipe_unlock(pipe);
1184 return ret;
1185}
1186
1187static const struct super_operations pipefs_ops = {
1188 .destroy_inode = free_inode_nonrcu,
1189 .statfs = simple_statfs,
1190};
1191
1192/*
1193 * pipefs should _never_ be mounted by userland - too much of security hassle,
1194 * no real gain from having the whole whorehouse mounted. So we don't need
1195 * any operations on the root directory. However, we need a non-trivial
1196 * d_name - pipe: will go nicely and kill the special-casing in procfs.
1197 */
1198static struct dentry *pipefs_mount(struct file_system_type *fs_type,
1199 int flags, const char *dev_name, void *data)
1200{
1201 return mount_pseudo(fs_type, "pipe:", &pipefs_ops,
1202 &pipefs_dentry_operations, PIPEFS_MAGIC);
1203}
1204
1205static struct file_system_type pipe_fs_type = {
1206 .name = "pipefs",
1207 .mount = pipefs_mount,
1208 .kill_sb = kill_anon_super,
1209};
1210
1211static int __init init_pipe_fs(void)
1212{
1213 int err = register_filesystem(&pipe_fs_type);
1214
1215 if (!err) {
1216 pipe_mnt = kern_mount(&pipe_fs_type);
1217 if (IS_ERR(pipe_mnt)) {
1218 err = PTR_ERR(pipe_mnt);
1219 unregister_filesystem(&pipe_fs_type);
1220 }
1221 }
1222 return err;
1223}
1224
1225fs_initcall(init_pipe_fs);