1 // SPDX-License-Identifier: GPL-2.0
5 * Copyright (C) 1991, 1992, 1999 Linus Torvalds
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>
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>
29 #include <linux/uaccess.h>
30 #include <asm/ioctls.h>
35 * New pipe buffers will be restricted to this size while the user is exceeding
36 * their pipe buffer quota. The general pipe use case needs at least two
37 * buffers: one for data yet to be read, and one for new data. If this is less
38 * than two, then a write to a non-empty pipe may block even if the pipe is not
39 * full. This can occur with GNU make jobserver or similar uses of pipes as
40 * semaphores: multiple processes may be waiting to write tokens back to the
41 * pipe before reading tokens: https://lore.kernel.org/lkml/1628086770.5rn8p04n6j.none@localhost/.
43 * Users can reduce their pipe buffers with F_SETPIPE_SZ below this at their
44 * own risk, namely: pipe writes to non-full pipes may block until the pipe is
47 #define PIPE_MIN_DEF_BUFFERS 2
50 * The max size that a non-root user is allowed to grow the pipe. Can
51 * be set by root in /proc/sys/fs/pipe-max-size
53 unsigned int pipe_max_size
= 1048576;
55 /* Maximum allocatable pages per user. Hard limit is unset by default, soft
56 * matches default values.
58 unsigned long pipe_user_pages_hard
;
59 unsigned long pipe_user_pages_soft
= PIPE_DEF_BUFFERS
* INR_OPEN_CUR
;
62 * We use head and tail indices that aren't masked off, except at the point of
63 * dereference, but rather they're allowed to wrap naturally. This means there
64 * isn't a dead spot in the buffer, but the ring has to be a power of two and
66 * -- David Howells 2019-09-23.
68 * Reads with count = 0 should always return 0.
69 * -- Julian Bradfield 1999-06-07.
71 * FIFOs and Pipes now generate SIGIO for both readers and writers.
72 * -- Jeremy Elson <jelson@circlemud.org> 2001-08-16
74 * pipe_read & write cleanup
75 * -- Manfred Spraul <manfred@colorfullife.com> 2002-05-09
78 static void pipe_lock_nested(struct pipe_inode_info
*pipe
, int subclass
)
81 mutex_lock_nested(&pipe
->mutex
, subclass
);
84 void pipe_lock(struct pipe_inode_info
*pipe
)
87 * pipe_lock() nests non-pipe inode locks (for writing to a file)
89 pipe_lock_nested(pipe
, I_MUTEX_PARENT
);
91 EXPORT_SYMBOL(pipe_lock
);
93 void pipe_unlock(struct pipe_inode_info
*pipe
)
96 mutex_unlock(&pipe
->mutex
);
98 EXPORT_SYMBOL(pipe_unlock
);
100 static inline void __pipe_lock(struct pipe_inode_info
*pipe
)
102 mutex_lock_nested(&pipe
->mutex
, I_MUTEX_PARENT
);
105 static inline void __pipe_unlock(struct pipe_inode_info
*pipe
)
107 mutex_unlock(&pipe
->mutex
);
110 void pipe_double_lock(struct pipe_inode_info
*pipe1
,
111 struct pipe_inode_info
*pipe2
)
113 BUG_ON(pipe1
== pipe2
);
116 pipe_lock_nested(pipe1
, I_MUTEX_PARENT
);
117 pipe_lock_nested(pipe2
, I_MUTEX_CHILD
);
119 pipe_lock_nested(pipe2
, I_MUTEX_PARENT
);
120 pipe_lock_nested(pipe1
, I_MUTEX_CHILD
);
124 static void anon_pipe_buf_release(struct pipe_inode_info
*pipe
,
125 struct pipe_buffer
*buf
)
127 struct page
*page
= buf
->page
;
130 * If nobody else uses this page, and we don't already have a
131 * temporary page, let's keep track of it as a one-deep
132 * allocation cache. (Otherwise just release our reference to it)
134 if (page_count(page
) == 1 && !pipe
->tmp_page
)
135 pipe
->tmp_page
= page
;
140 static bool anon_pipe_buf_try_steal(struct pipe_inode_info
*pipe
,
141 struct pipe_buffer
*buf
)
143 struct page
*page
= buf
->page
;
145 if (page_count(page
) != 1)
147 memcg_kmem_uncharge_page(page
, 0);
148 __SetPageLocked(page
);
153 * generic_pipe_buf_try_steal - attempt to take ownership of a &pipe_buffer
154 * @pipe: the pipe that the buffer belongs to
155 * @buf: the buffer to attempt to steal
158 * This function attempts to steal the &struct page attached to
159 * @buf. If successful, this function returns 0 and returns with
160 * the page locked. The caller may then reuse the page for whatever
161 * he wishes; the typical use is insertion into a different file
164 bool generic_pipe_buf_try_steal(struct pipe_inode_info
*pipe
,
165 struct pipe_buffer
*buf
)
167 struct page
*page
= buf
->page
;
170 * A reference of one is golden, that means that the owner of this
171 * page is the only one holding a reference to it. lock the page
174 if (page_count(page
) == 1) {
180 EXPORT_SYMBOL(generic_pipe_buf_try_steal
);
183 * generic_pipe_buf_get - get a reference to a &struct pipe_buffer
184 * @pipe: the pipe that the buffer belongs to
185 * @buf: the buffer to get a reference to
188 * This function grabs an extra reference to @buf. It's used in
189 * the tee() system call, when we duplicate the buffers in one
192 bool generic_pipe_buf_get(struct pipe_inode_info
*pipe
, struct pipe_buffer
*buf
)
194 return try_get_page(buf
->page
);
196 EXPORT_SYMBOL(generic_pipe_buf_get
);
199 * generic_pipe_buf_release - put a reference to a &struct pipe_buffer
200 * @pipe: the pipe that the buffer belongs to
201 * @buf: the buffer to put a reference to
204 * This function releases a reference to @buf.
206 void generic_pipe_buf_release(struct pipe_inode_info
*pipe
,
207 struct pipe_buffer
*buf
)
211 EXPORT_SYMBOL(generic_pipe_buf_release
);
213 static const struct pipe_buf_operations anon_pipe_buf_ops
= {
214 .release
= anon_pipe_buf_release
,
215 .try_steal
= anon_pipe_buf_try_steal
,
216 .get
= generic_pipe_buf_get
,
219 /* Done while waiting without holding the pipe lock - thus the READ_ONCE() */
220 static inline bool pipe_readable(const struct pipe_inode_info
*pipe
)
222 unsigned int head
= READ_ONCE(pipe
->head
);
223 unsigned int tail
= READ_ONCE(pipe
->tail
);
224 unsigned int writers
= READ_ONCE(pipe
->writers
);
226 return !pipe_empty(head
, tail
) || !writers
;
230 pipe_read(struct kiocb
*iocb
, struct iov_iter
*to
)
232 size_t total_len
= iov_iter_count(to
);
233 struct file
*filp
= iocb
->ki_filp
;
234 struct pipe_inode_info
*pipe
= filp
->private_data
;
235 bool was_full
, wake_next_reader
= false;
238 /* Null read succeeds. */
239 if (unlikely(total_len
== 0))
246 * We only wake up writers if the pipe was full when we started
247 * reading in order to avoid unnecessary wakeups.
249 * But when we do wake up writers, we do so using a sync wakeup
250 * (WF_SYNC), because we want them to get going and generate more
253 was_full
= pipe_full(pipe
->head
, pipe
->tail
, pipe
->max_usage
);
255 unsigned int head
= pipe
->head
;
256 unsigned int tail
= pipe
->tail
;
257 unsigned int mask
= pipe
->ring_size
- 1;
259 #ifdef CONFIG_WATCH_QUEUE
260 if (pipe
->note_loss
) {
261 struct watch_notification n
;
269 n
.type
= WATCH_TYPE_META
;
270 n
.subtype
= WATCH_META_LOSS_NOTIFICATION
;
271 n
.info
= watch_sizeof(n
);
272 if (copy_to_iter(&n
, sizeof(n
), to
) != sizeof(n
)) {
278 total_len
-= sizeof(n
);
279 pipe
->note_loss
= false;
283 if (!pipe_empty(head
, tail
)) {
284 struct pipe_buffer
*buf
= &pipe
->bufs
[tail
& mask
];
285 size_t chars
= buf
->len
;
289 if (chars
> total_len
) {
290 if (buf
->flags
& PIPE_BUF_FLAG_WHOLE
) {
298 error
= pipe_buf_confirm(pipe
, buf
);
305 written
= copy_page_to_iter(buf
->page
, buf
->offset
, chars
, to
);
306 if (unlikely(written
< chars
)) {
312 buf
->offset
+= chars
;
315 /* Was it a packet buffer? Clean up and exit */
316 if (buf
->flags
& PIPE_BUF_FLAG_PACKET
) {
322 pipe_buf_release(pipe
, buf
);
323 spin_lock_irq(&pipe
->rd_wait
.lock
);
324 #ifdef CONFIG_WATCH_QUEUE
325 if (buf
->flags
& PIPE_BUF_FLAG_LOSS
)
326 pipe
->note_loss
= true;
330 spin_unlock_irq(&pipe
->rd_wait
.lock
);
334 break; /* common path: read succeeded */
335 if (!pipe_empty(head
, tail
)) /* More to do? */
343 if (filp
->f_flags
& O_NONBLOCK
) {
350 * We only get here if we didn't actually read anything.
352 * However, we could have seen (and removed) a zero-sized
353 * pipe buffer, and might have made space in the buffers
356 * You can't make zero-sized pipe buffers by doing an empty
357 * write (not even in packet mode), but they can happen if
358 * the writer gets an EFAULT when trying to fill a buffer
359 * that already got allocated and inserted in the buffer
362 * So we still need to wake up any pending writers in the
363 * _very_ unlikely case that the pipe was full, but we got
366 if (unlikely(was_full
))
367 wake_up_interruptible_sync_poll(&pipe
->wr_wait
, EPOLLOUT
| EPOLLWRNORM
);
368 kill_fasync(&pipe
->fasync_writers
, SIGIO
, POLL_OUT
);
371 * But because we didn't read anything, at this point we can
372 * just return directly with -ERESTARTSYS if we're interrupted,
373 * since we've done any required wakeups and there's no need
374 * to mark anything accessed. And we've dropped the lock.
376 if (wait_event_interruptible_exclusive(pipe
->rd_wait
, pipe_readable(pipe
)) < 0)
380 was_full
= pipe_full(pipe
->head
, pipe
->tail
, pipe
->max_usage
);
381 wake_next_reader
= true;
383 if (pipe_empty(pipe
->head
, pipe
->tail
))
384 wake_next_reader
= false;
388 wake_up_interruptible_sync_poll(&pipe
->wr_wait
, EPOLLOUT
| EPOLLWRNORM
);
389 if (wake_next_reader
)
390 wake_up_interruptible_sync_poll(&pipe
->rd_wait
, EPOLLIN
| EPOLLRDNORM
);
391 kill_fasync(&pipe
->fasync_writers
, SIGIO
, POLL_OUT
);
397 static inline int is_packetized(struct file
*file
)
399 return (file
->f_flags
& O_DIRECT
) != 0;
402 /* Done while waiting without holding the pipe lock - thus the READ_ONCE() */
403 static inline bool pipe_writable(const struct pipe_inode_info
*pipe
)
405 unsigned int head
= READ_ONCE(pipe
->head
);
406 unsigned int tail
= READ_ONCE(pipe
->tail
);
407 unsigned int max_usage
= READ_ONCE(pipe
->max_usage
);
409 return !pipe_full(head
, tail
, max_usage
) ||
410 !READ_ONCE(pipe
->readers
);
414 pipe_write(struct kiocb
*iocb
, struct iov_iter
*from
)
416 struct file
*filp
= iocb
->ki_filp
;
417 struct pipe_inode_info
*pipe
= filp
->private_data
;
420 size_t total_len
= iov_iter_count(from
);
422 bool was_empty
= false;
423 bool wake_next_writer
= false;
425 /* Null write succeeds. */
426 if (unlikely(total_len
== 0))
431 if (!pipe
->readers
) {
432 send_sig(SIGPIPE
, current
, 0);
437 #ifdef CONFIG_WATCH_QUEUE
438 if (pipe
->watch_queue
) {
445 * If it wasn't empty we try to merge new data into
448 * That naturally merges small writes, but it also
449 * page-aligns the rest of the writes for large writes
450 * spanning multiple pages.
453 was_empty
= pipe_empty(head
, pipe
->tail
);
454 chars
= total_len
& (PAGE_SIZE
-1);
455 if (chars
&& !was_empty
) {
456 unsigned int mask
= pipe
->ring_size
- 1;
457 struct pipe_buffer
*buf
= &pipe
->bufs
[(head
- 1) & mask
];
458 int offset
= buf
->offset
+ buf
->len
;
460 if ((buf
->flags
& PIPE_BUF_FLAG_CAN_MERGE
) &&
461 offset
+ chars
<= PAGE_SIZE
) {
462 ret
= pipe_buf_confirm(pipe
, buf
);
466 ret
= copy_page_from_iter(buf
->page
, offset
, chars
, from
);
467 if (unlikely(ret
< chars
)) {
473 if (!iov_iter_count(from
))
479 if (!pipe
->readers
) {
480 send_sig(SIGPIPE
, current
, 0);
487 if (!pipe_full(head
, pipe
->tail
, pipe
->max_usage
)) {
488 unsigned int mask
= pipe
->ring_size
- 1;
489 struct pipe_buffer
*buf
= &pipe
->bufs
[head
& mask
];
490 struct page
*page
= pipe
->tmp_page
;
494 page
= alloc_page(GFP_HIGHUSER
| __GFP_ACCOUNT
);
495 if (unlikely(!page
)) {
496 ret
= ret
? : -ENOMEM
;
499 pipe
->tmp_page
= page
;
502 /* Allocate a slot in the ring in advance and attach an
503 * empty buffer. If we fault or otherwise fail to use
504 * it, either the reader will consume it or it'll still
505 * be there for the next write.
507 spin_lock_irq(&pipe
->rd_wait
.lock
);
510 if (pipe_full(head
, pipe
->tail
, pipe
->max_usage
)) {
511 spin_unlock_irq(&pipe
->rd_wait
.lock
);
515 pipe
->head
= head
+ 1;
516 spin_unlock_irq(&pipe
->rd_wait
.lock
);
518 /* Insert it into the buffer array */
519 buf
= &pipe
->bufs
[head
& mask
];
521 buf
->ops
= &anon_pipe_buf_ops
;
524 if (is_packetized(filp
))
525 buf
->flags
= PIPE_BUF_FLAG_PACKET
;
527 buf
->flags
= PIPE_BUF_FLAG_CAN_MERGE
;
528 pipe
->tmp_page
= NULL
;
530 copied
= copy_page_from_iter(page
, 0, PAGE_SIZE
, from
);
531 if (unlikely(copied
< PAGE_SIZE
&& iov_iter_count(from
))) {
540 if (!iov_iter_count(from
))
544 if (!pipe_full(head
, pipe
->tail
, pipe
->max_usage
))
547 /* Wait for buffer space to become available. */
548 if (filp
->f_flags
& O_NONBLOCK
) {
553 if (signal_pending(current
)) {
560 * We're going to release the pipe lock and wait for more
561 * space. We wake up any readers if necessary, and then
562 * after waiting we need to re-check whether the pipe
563 * become empty while we dropped the lock.
567 wake_up_interruptible_sync_poll(&pipe
->rd_wait
, EPOLLIN
| EPOLLRDNORM
);
568 kill_fasync(&pipe
->fasync_readers
, SIGIO
, POLL_IN
);
569 wait_event_interruptible_exclusive(pipe
->wr_wait
, pipe_writable(pipe
));
571 was_empty
= pipe_empty(pipe
->head
, pipe
->tail
);
572 wake_next_writer
= true;
575 if (pipe_full(pipe
->head
, pipe
->tail
, pipe
->max_usage
))
576 wake_next_writer
= false;
580 * If we do do a wakeup event, we do a 'sync' wakeup, because we
581 * want the reader to start processing things asap, rather than
582 * leave the data pending.
584 * This is particularly important for small writes, because of
585 * how (for example) the GNU make jobserver uses small writes to
586 * wake up pending jobs
588 * Epoll nonsensically wants a wakeup whether the pipe
589 * was already empty or not.
591 if (was_empty
|| pipe
->poll_usage
)
592 wake_up_interruptible_sync_poll(&pipe
->rd_wait
, EPOLLIN
| EPOLLRDNORM
);
593 kill_fasync(&pipe
->fasync_readers
, SIGIO
, POLL_IN
);
594 if (wake_next_writer
)
595 wake_up_interruptible_sync_poll(&pipe
->wr_wait
, EPOLLOUT
| EPOLLWRNORM
);
596 if (ret
> 0 && sb_start_write_trylock(file_inode(filp
)->i_sb
)) {
597 int err
= file_update_time(filp
);
600 sb_end_write(file_inode(filp
)->i_sb
);
605 static long pipe_ioctl(struct file
*filp
, unsigned int cmd
, unsigned long arg
)
607 struct pipe_inode_info
*pipe
= filp
->private_data
;
608 int count
, head
, tail
, mask
;
616 mask
= pipe
->ring_size
- 1;
618 while (tail
!= head
) {
619 count
+= pipe
->bufs
[tail
& mask
].len
;
624 return put_user(count
, (int __user
*)arg
);
626 #ifdef CONFIG_WATCH_QUEUE
627 case IOC_WATCH_QUEUE_SET_SIZE
: {
630 ret
= watch_queue_set_size(pipe
, arg
);
635 case IOC_WATCH_QUEUE_SET_FILTER
:
636 return watch_queue_set_filter(
637 pipe
, (struct watch_notification_filter __user
*)arg
);
645 /* No kernel lock held - fine */
647 pipe_poll(struct file
*filp
, poll_table
*wait
)
650 struct pipe_inode_info
*pipe
= filp
->private_data
;
651 unsigned int head
, tail
;
653 /* Epoll has some historical nasty semantics, this enables them */
654 pipe
->poll_usage
= 1;
657 * Reading pipe state only -- no need for acquiring the semaphore.
659 * But because this is racy, the code has to add the
660 * entry to the poll table _first_ ..
662 if (filp
->f_mode
& FMODE_READ
)
663 poll_wait(filp
, &pipe
->rd_wait
, wait
);
664 if (filp
->f_mode
& FMODE_WRITE
)
665 poll_wait(filp
, &pipe
->wr_wait
, wait
);
668 * .. and only then can you do the racy tests. That way,
669 * if something changes and you got it wrong, the poll
670 * table entry will wake you up and fix it.
672 head
= READ_ONCE(pipe
->head
);
673 tail
= READ_ONCE(pipe
->tail
);
676 if (filp
->f_mode
& FMODE_READ
) {
677 if (!pipe_empty(head
, tail
))
678 mask
|= EPOLLIN
| EPOLLRDNORM
;
679 if (!pipe
->writers
&& filp
->f_version
!= pipe
->w_counter
)
683 if (filp
->f_mode
& FMODE_WRITE
) {
684 if (!pipe_full(head
, tail
, pipe
->max_usage
))
685 mask
|= EPOLLOUT
| EPOLLWRNORM
;
687 * Most Unices do not set EPOLLERR for FIFOs but on Linux they
688 * behave exactly like pipes for poll().
697 static void put_pipe_info(struct inode
*inode
, struct pipe_inode_info
*pipe
)
701 spin_lock(&inode
->i_lock
);
702 if (!--pipe
->files
) {
703 inode
->i_pipe
= NULL
;
706 spin_unlock(&inode
->i_lock
);
709 free_pipe_info(pipe
);
713 pipe_release(struct inode
*inode
, struct file
*file
)
715 struct pipe_inode_info
*pipe
= file
->private_data
;
718 if (file
->f_mode
& FMODE_READ
)
720 if (file
->f_mode
& FMODE_WRITE
)
723 /* Was that the last reader or writer, but not the other side? */
724 if (!pipe
->readers
!= !pipe
->writers
) {
725 wake_up_interruptible_all(&pipe
->rd_wait
);
726 wake_up_interruptible_all(&pipe
->wr_wait
);
727 kill_fasync(&pipe
->fasync_readers
, SIGIO
, POLL_IN
);
728 kill_fasync(&pipe
->fasync_writers
, SIGIO
, POLL_OUT
);
732 put_pipe_info(inode
, pipe
);
737 pipe_fasync(int fd
, struct file
*filp
, int on
)
739 struct pipe_inode_info
*pipe
= filp
->private_data
;
743 if (filp
->f_mode
& FMODE_READ
)
744 retval
= fasync_helper(fd
, filp
, on
, &pipe
->fasync_readers
);
745 if ((filp
->f_mode
& FMODE_WRITE
) && retval
>= 0) {
746 retval
= fasync_helper(fd
, filp
, on
, &pipe
->fasync_writers
);
747 if (retval
< 0 && (filp
->f_mode
& FMODE_READ
))
748 /* this can happen only if on == T */
749 fasync_helper(-1, filp
, 0, &pipe
->fasync_readers
);
755 unsigned long account_pipe_buffers(struct user_struct
*user
,
756 unsigned long old
, unsigned long new)
758 return atomic_long_add_return(new - old
, &user
->pipe_bufs
);
761 bool too_many_pipe_buffers_soft(unsigned long user_bufs
)
763 unsigned long soft_limit
= READ_ONCE(pipe_user_pages_soft
);
765 return soft_limit
&& user_bufs
> soft_limit
;
768 bool too_many_pipe_buffers_hard(unsigned long user_bufs
)
770 unsigned long hard_limit
= READ_ONCE(pipe_user_pages_hard
);
772 return hard_limit
&& user_bufs
> hard_limit
;
775 bool pipe_is_unprivileged_user(void)
777 return !capable(CAP_SYS_RESOURCE
) && !capable(CAP_SYS_ADMIN
);
780 struct pipe_inode_info
*alloc_pipe_info(void)
782 struct pipe_inode_info
*pipe
;
783 unsigned long pipe_bufs
= PIPE_DEF_BUFFERS
;
784 struct user_struct
*user
= get_current_user();
785 unsigned long user_bufs
;
786 unsigned int max_size
= READ_ONCE(pipe_max_size
);
788 pipe
= kzalloc(sizeof(struct pipe_inode_info
), GFP_KERNEL_ACCOUNT
);
792 if (pipe_bufs
* PAGE_SIZE
> max_size
&& !capable(CAP_SYS_RESOURCE
))
793 pipe_bufs
= max_size
>> PAGE_SHIFT
;
795 user_bufs
= account_pipe_buffers(user
, 0, pipe_bufs
);
797 if (too_many_pipe_buffers_soft(user_bufs
) && pipe_is_unprivileged_user()) {
798 user_bufs
= account_pipe_buffers(user
, pipe_bufs
, PIPE_MIN_DEF_BUFFERS
);
799 pipe_bufs
= PIPE_MIN_DEF_BUFFERS
;
802 if (too_many_pipe_buffers_hard(user_bufs
) && pipe_is_unprivileged_user())
803 goto out_revert_acct
;
805 pipe
->bufs
= kcalloc(pipe_bufs
, sizeof(struct pipe_buffer
),
809 init_waitqueue_head(&pipe
->rd_wait
);
810 init_waitqueue_head(&pipe
->wr_wait
);
811 pipe
->r_counter
= pipe
->w_counter
= 1;
812 pipe
->max_usage
= pipe_bufs
;
813 pipe
->ring_size
= pipe_bufs
;
814 pipe
->nr_accounted
= pipe_bufs
;
816 mutex_init(&pipe
->mutex
);
821 (void) account_pipe_buffers(user
, pipe_bufs
, 0);
828 void free_pipe_info(struct pipe_inode_info
*pipe
)
832 #ifdef CONFIG_WATCH_QUEUE
833 if (pipe
->watch_queue
) {
834 watch_queue_clear(pipe
->watch_queue
);
835 put_watch_queue(pipe
->watch_queue
);
839 (void) account_pipe_buffers(pipe
->user
, pipe
->nr_accounted
, 0);
840 free_uid(pipe
->user
);
841 for (i
= 0; i
< pipe
->ring_size
; i
++) {
842 struct pipe_buffer
*buf
= pipe
->bufs
+ i
;
844 pipe_buf_release(pipe
, buf
);
847 __free_page(pipe
->tmp_page
);
852 static struct vfsmount
*pipe_mnt __read_mostly
;
855 * pipefs_dname() is called from d_path().
857 static char *pipefs_dname(struct dentry
*dentry
, char *buffer
, int buflen
)
859 return dynamic_dname(dentry
, buffer
, buflen
, "pipe:[%lu]",
860 d_inode(dentry
)->i_ino
);
863 static const struct dentry_operations pipefs_dentry_operations
= {
864 .d_dname
= pipefs_dname
,
867 static struct inode
* get_pipe_inode(void)
869 struct inode
*inode
= new_inode_pseudo(pipe_mnt
->mnt_sb
);
870 struct pipe_inode_info
*pipe
;
875 inode
->i_ino
= get_next_ino();
877 pipe
= alloc_pipe_info();
881 inode
->i_pipe
= pipe
;
883 pipe
->readers
= pipe
->writers
= 1;
884 inode
->i_fop
= &pipefifo_fops
;
887 * Mark the inode dirty from the very beginning,
888 * that way it will never be moved to the dirty
889 * list because "mark_inode_dirty()" will think
890 * that it already _is_ on the dirty list.
892 inode
->i_state
= I_DIRTY
;
893 inode
->i_mode
= S_IFIFO
| S_IRUSR
| S_IWUSR
;
894 inode
->i_uid
= current_fsuid();
895 inode
->i_gid
= current_fsgid();
896 inode
->i_atime
= inode
->i_mtime
= inode
->i_ctime
= current_time(inode
);
907 int create_pipe_files(struct file
**res
, int flags
)
909 struct inode
*inode
= get_pipe_inode();
916 if (flags
& O_NOTIFICATION_PIPE
) {
917 error
= watch_queue_init(inode
->i_pipe
);
919 free_pipe_info(inode
->i_pipe
);
925 f
= alloc_file_pseudo(inode
, pipe_mnt
, "",
926 O_WRONLY
| (flags
& (O_NONBLOCK
| O_DIRECT
)),
929 free_pipe_info(inode
->i_pipe
);
934 f
->private_data
= inode
->i_pipe
;
936 res
[0] = alloc_file_clone(f
, O_RDONLY
| (flags
& O_NONBLOCK
),
938 if (IS_ERR(res
[0])) {
939 put_pipe_info(inode
, inode
->i_pipe
);
941 return PTR_ERR(res
[0]);
943 res
[0]->private_data
= inode
->i_pipe
;
945 stream_open(inode
, res
[0]);
946 stream_open(inode
, res
[1]);
950 static int __do_pipe_flags(int *fd
, struct file
**files
, int flags
)
955 if (flags
& ~(O_CLOEXEC
| O_NONBLOCK
| O_DIRECT
| O_NOTIFICATION_PIPE
))
958 error
= create_pipe_files(files
, flags
);
962 error
= get_unused_fd_flags(flags
);
967 error
= get_unused_fd_flags(flags
);
972 audit_fd_pair(fdr
, fdw
);
985 int do_pipe_flags(int *fd
, int flags
)
987 struct file
*files
[2];
988 int error
= __do_pipe_flags(fd
, files
, flags
);
990 fd_install(fd
[0], files
[0]);
991 fd_install(fd
[1], files
[1]);
997 * sys_pipe() is the normal C calling standard for creating
998 * a pipe. It's not the way Unix traditionally does this, though.
1000 static int do_pipe2(int __user
*fildes
, int flags
)
1002 struct file
*files
[2];
1006 error
= __do_pipe_flags(fd
, files
, flags
);
1008 if (unlikely(copy_to_user(fildes
, fd
, sizeof(fd
)))) {
1011 put_unused_fd(fd
[0]);
1012 put_unused_fd(fd
[1]);
1015 fd_install(fd
[0], files
[0]);
1016 fd_install(fd
[1], files
[1]);
1022 SYSCALL_DEFINE2(pipe2
, int __user
*, fildes
, int, flags
)
1024 return do_pipe2(fildes
, flags
);
1027 SYSCALL_DEFINE1(pipe
, int __user
*, fildes
)
1029 return do_pipe2(fildes
, 0);
1033 * This is the stupid "wait for pipe to be readable or writable"
1036 * See pipe_read/write() for the proper kind of exclusive wait,
1037 * but that requires that we wake up any other readers/writers
1038 * if we then do not end up reading everything (ie the whole
1039 * "wake_next_reader/writer" logic in pipe_read/write()).
1041 void pipe_wait_readable(struct pipe_inode_info
*pipe
)
1044 wait_event_interruptible(pipe
->rd_wait
, pipe_readable(pipe
));
1048 void pipe_wait_writable(struct pipe_inode_info
*pipe
)
1051 wait_event_interruptible(pipe
->wr_wait
, pipe_writable(pipe
));
1056 * This depends on both the wait (here) and the wakeup (wake_up_partner)
1057 * holding the pipe lock, so "*cnt" is stable and we know a wakeup cannot
1058 * race with the count check and waitqueue prep.
1060 * Normally in order to avoid races, you'd do the prepare_to_wait() first,
1061 * then check the condition you're waiting for, and only then sleep. But
1062 * because of the pipe lock, we can check the condition before being on
1065 * We use the 'rd_wait' waitqueue for pipe partner waiting.
1067 static int wait_for_partner(struct pipe_inode_info
*pipe
, unsigned int *cnt
)
1069 DEFINE_WAIT(rdwait
);
1072 while (cur
== *cnt
) {
1073 prepare_to_wait(&pipe
->rd_wait
, &rdwait
, TASK_INTERRUPTIBLE
);
1076 finish_wait(&pipe
->rd_wait
, &rdwait
);
1078 if (signal_pending(current
))
1081 return cur
== *cnt
? -ERESTARTSYS
: 0;
1084 static void wake_up_partner(struct pipe_inode_info
*pipe
)
1086 wake_up_interruptible_all(&pipe
->rd_wait
);
1089 static int fifo_open(struct inode
*inode
, struct file
*filp
)
1091 struct pipe_inode_info
*pipe
;
1092 bool is_pipe
= inode
->i_sb
->s_magic
== PIPEFS_MAGIC
;
1095 filp
->f_version
= 0;
1097 spin_lock(&inode
->i_lock
);
1098 if (inode
->i_pipe
) {
1099 pipe
= inode
->i_pipe
;
1101 spin_unlock(&inode
->i_lock
);
1103 spin_unlock(&inode
->i_lock
);
1104 pipe
= alloc_pipe_info();
1108 spin_lock(&inode
->i_lock
);
1109 if (unlikely(inode
->i_pipe
)) {
1110 inode
->i_pipe
->files
++;
1111 spin_unlock(&inode
->i_lock
);
1112 free_pipe_info(pipe
);
1113 pipe
= inode
->i_pipe
;
1115 inode
->i_pipe
= pipe
;
1116 spin_unlock(&inode
->i_lock
);
1119 filp
->private_data
= pipe
;
1120 /* OK, we have a pipe and it's pinned down */
1124 /* We can only do regular read/write on fifos */
1125 stream_open(inode
, filp
);
1127 switch (filp
->f_mode
& (FMODE_READ
| FMODE_WRITE
)) {
1131 * POSIX.1 says that O_NONBLOCK means return with the FIFO
1132 * opened, even when there is no process writing the FIFO.
1135 if (pipe
->readers
++ == 0)
1136 wake_up_partner(pipe
);
1138 if (!is_pipe
&& !pipe
->writers
) {
1139 if ((filp
->f_flags
& O_NONBLOCK
)) {
1140 /* suppress EPOLLHUP until we have
1142 filp
->f_version
= pipe
->w_counter
;
1144 if (wait_for_partner(pipe
, &pipe
->w_counter
))
1153 * POSIX.1 says that O_NONBLOCK means return -1 with
1154 * errno=ENXIO when there is no process reading the FIFO.
1157 if (!is_pipe
&& (filp
->f_flags
& O_NONBLOCK
) && !pipe
->readers
)
1161 if (!pipe
->writers
++)
1162 wake_up_partner(pipe
);
1164 if (!is_pipe
&& !pipe
->readers
) {
1165 if (wait_for_partner(pipe
, &pipe
->r_counter
))
1170 case FMODE_READ
| FMODE_WRITE
:
1173 * POSIX.1 leaves this case "undefined" when O_NONBLOCK is set.
1174 * This implementation will NEVER block on a O_RDWR open, since
1175 * the process can at least talk to itself.
1182 if (pipe
->readers
== 1 || pipe
->writers
== 1)
1183 wake_up_partner(pipe
);
1192 __pipe_unlock(pipe
);
1196 if (!--pipe
->readers
)
1197 wake_up_interruptible(&pipe
->wr_wait
);
1202 if (!--pipe
->writers
)
1203 wake_up_interruptible_all(&pipe
->rd_wait
);
1208 __pipe_unlock(pipe
);
1210 put_pipe_info(inode
, pipe
);
1214 const struct file_operations pipefifo_fops
= {
1216 .llseek
= no_llseek
,
1217 .read_iter
= pipe_read
,
1218 .write_iter
= pipe_write
,
1220 .unlocked_ioctl
= pipe_ioctl
,
1221 .release
= pipe_release
,
1222 .fasync
= pipe_fasync
,
1223 .splice_write
= iter_file_splice_write
,
1227 * Currently we rely on the pipe array holding a power-of-2 number
1228 * of pages. Returns 0 on error.
1230 unsigned int round_pipe_size(unsigned long size
)
1232 if (size
> (1U << 31))
1235 /* Minimum pipe size, as required by POSIX */
1236 if (size
< PAGE_SIZE
)
1239 return roundup_pow_of_two(size
);
1243 * Resize the pipe ring to a number of slots.
1245 int pipe_resize_ring(struct pipe_inode_info
*pipe
, unsigned int nr_slots
)
1247 struct pipe_buffer
*bufs
;
1248 unsigned int head
, tail
, mask
, n
;
1251 * We can shrink the pipe, if arg is greater than the ring occupancy.
1252 * Since we don't expect a lot of shrink+grow operations, just free and
1253 * allocate again like we would do for growing. If the pipe currently
1254 * contains more buffers than arg, then return busy.
1256 mask
= pipe
->ring_size
- 1;
1259 n
= pipe_occupancy(pipe
->head
, pipe
->tail
);
1263 bufs
= kcalloc(nr_slots
, sizeof(*bufs
),
1264 GFP_KERNEL_ACCOUNT
| __GFP_NOWARN
);
1265 if (unlikely(!bufs
))
1269 * The pipe array wraps around, so just start the new one at zero
1270 * and adjust the indices.
1273 unsigned int h
= head
& mask
;
1274 unsigned int t
= tail
& mask
;
1276 memcpy(bufs
, pipe
->bufs
+ t
,
1277 n
* sizeof(struct pipe_buffer
));
1279 unsigned int tsize
= pipe
->ring_size
- t
;
1281 memcpy(bufs
+ tsize
, pipe
->bufs
,
1282 h
* sizeof(struct pipe_buffer
));
1283 memcpy(bufs
, pipe
->bufs
+ t
,
1284 tsize
* sizeof(struct pipe_buffer
));
1293 pipe
->ring_size
= nr_slots
;
1294 if (pipe
->max_usage
> nr_slots
)
1295 pipe
->max_usage
= nr_slots
;
1299 /* This might have made more room for writers */
1300 wake_up_interruptible(&pipe
->wr_wait
);
1305 * Allocate a new array of pipe buffers and copy the info over. Returns the
1306 * pipe size if successful, or return -ERROR on error.
1308 static long pipe_set_size(struct pipe_inode_info
*pipe
, unsigned long arg
)
1310 unsigned long user_bufs
;
1311 unsigned int nr_slots
, size
;
1314 #ifdef CONFIG_WATCH_QUEUE
1315 if (pipe
->watch_queue
)
1319 size
= round_pipe_size(arg
);
1320 nr_slots
= size
>> PAGE_SHIFT
;
1326 * If trying to increase the pipe capacity, check that an
1327 * unprivileged user is not trying to exceed various limits
1328 * (soft limit check here, hard limit check just below).
1329 * Decreasing the pipe capacity is always permitted, even
1330 * if the user is currently over a limit.
1332 if (nr_slots
> pipe
->max_usage
&&
1333 size
> pipe_max_size
&& !capable(CAP_SYS_RESOURCE
))
1336 user_bufs
= account_pipe_buffers(pipe
->user
, pipe
->nr_accounted
, nr_slots
);
1338 if (nr_slots
> pipe
->max_usage
&&
1339 (too_many_pipe_buffers_hard(user_bufs
) ||
1340 too_many_pipe_buffers_soft(user_bufs
)) &&
1341 pipe_is_unprivileged_user()) {
1343 goto out_revert_acct
;
1346 ret
= pipe_resize_ring(pipe
, nr_slots
);
1348 goto out_revert_acct
;
1350 pipe
->max_usage
= nr_slots
;
1351 pipe
->nr_accounted
= nr_slots
;
1352 return pipe
->max_usage
* PAGE_SIZE
;
1355 (void) account_pipe_buffers(pipe
->user
, nr_slots
, pipe
->nr_accounted
);
1360 * Note that i_pipe and i_cdev share the same location, so checking ->i_pipe is
1361 * not enough to verify that this is a pipe.
1363 struct pipe_inode_info
*get_pipe_info(struct file
*file
, bool for_splice
)
1365 struct pipe_inode_info
*pipe
= file
->private_data
;
1367 if (file
->f_op
!= &pipefifo_fops
|| !pipe
)
1369 #ifdef CONFIG_WATCH_QUEUE
1370 if (for_splice
&& pipe
->watch_queue
)
1376 long pipe_fcntl(struct file
*file
, unsigned int cmd
, unsigned long arg
)
1378 struct pipe_inode_info
*pipe
;
1381 pipe
= get_pipe_info(file
, false);
1389 ret
= pipe_set_size(pipe
, arg
);
1392 ret
= pipe
->max_usage
* PAGE_SIZE
;
1399 __pipe_unlock(pipe
);
1403 static const struct super_operations pipefs_ops
= {
1404 .destroy_inode
= free_inode_nonrcu
,
1405 .statfs
= simple_statfs
,
1409 * pipefs should _never_ be mounted by userland - too much of security hassle,
1410 * no real gain from having the whole whorehouse mounted. So we don't need
1411 * any operations on the root directory. However, we need a non-trivial
1412 * d_name - pipe: will go nicely and kill the special-casing in procfs.
1415 static int pipefs_init_fs_context(struct fs_context
*fc
)
1417 struct pseudo_fs_context
*ctx
= init_pseudo(fc
, PIPEFS_MAGIC
);
1420 ctx
->ops
= &pipefs_ops
;
1421 ctx
->dops
= &pipefs_dentry_operations
;
1425 static struct file_system_type pipe_fs_type
= {
1427 .init_fs_context
= pipefs_init_fs_context
,
1428 .kill_sb
= kill_anon_super
,
1431 static int __init
init_pipe_fs(void)
1433 int err
= register_filesystem(&pipe_fs_type
);
1436 pipe_mnt
= kern_mount(&pipe_fs_type
);
1437 if (IS_ERR(pipe_mnt
)) {
1438 err
= PTR_ERR(pipe_mnt
);
1439 unregister_filesystem(&pipe_fs_type
);
1445 fs_initcall(init_pipe_fs
);