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>
28 #include <linux/sysctl.h>
30 #include <linux/uaccess.h>
31 #include <asm/ioctls.h>
36 * New pipe buffers will be restricted to this size while the user is exceeding
37 * their pipe buffer quota. The general pipe use case needs at least two
38 * buffers: one for data yet to be read, and one for new data. If this is less
39 * than two, then a write to a non-empty pipe may block even if the pipe is not
40 * full. This can occur with GNU make jobserver or similar uses of pipes as
41 * semaphores: multiple processes may be waiting to write tokens back to the
42 * pipe before reading tokens: https://lore.kernel.org/lkml/1628086770.5rn8p04n6j.none@localhost/.
44 * Users can reduce their pipe buffers with F_SETPIPE_SZ below this at their
45 * own risk, namely: pipe writes to non-full pipes may block until the pipe is
48 #define PIPE_MIN_DEF_BUFFERS 2
51 * The max size that a non-root user is allowed to grow the pipe. Can
52 * be set by root in /proc/sys/fs/pipe-max-size
54 static unsigned int pipe_max_size = 1048576;
56 /* Maximum allocatable pages per user. Hard limit is unset by default, soft
57 * matches default values.
59 static unsigned long pipe_user_pages_hard;
60 static unsigned long pipe_user_pages_soft = PIPE_DEF_BUFFERS * INR_OPEN_CUR;
63 * We use head and tail indices that aren't masked off, except at the point of
64 * dereference, but rather they're allowed to wrap naturally. This means there
65 * isn't a dead spot in the buffer, but the ring has to be a power of two and
67 * -- David Howells 2019-09-23.
69 * Reads with count = 0 should always return 0.
70 * -- Julian Bradfield 1999-06-07.
72 * FIFOs and Pipes now generate SIGIO for both readers and writers.
73 * -- Jeremy Elson <jelson@circlemud.org> 2001-08-16
75 * pipe_read & write cleanup
76 * -- Manfred Spraul <manfred@colorfullife.com> 2002-05-09
79 static void pipe_lock_nested(struct pipe_inode_info *pipe, int subclass)
82 mutex_lock_nested(&pipe->mutex, subclass);
85 void pipe_lock(struct pipe_inode_info *pipe)
88 * pipe_lock() nests non-pipe inode locks (for writing to a file)
90 pipe_lock_nested(pipe, I_MUTEX_PARENT);
92 EXPORT_SYMBOL(pipe_lock);
94 void pipe_unlock(struct pipe_inode_info *pipe)
97 mutex_unlock(&pipe->mutex);
99 EXPORT_SYMBOL(pipe_unlock);
101 static inline void __pipe_lock(struct pipe_inode_info *pipe)
103 mutex_lock_nested(&pipe->mutex, I_MUTEX_PARENT);
106 static inline void __pipe_unlock(struct pipe_inode_info *pipe)
108 mutex_unlock(&pipe->mutex);
111 void pipe_double_lock(struct pipe_inode_info *pipe1,
112 struct pipe_inode_info *pipe2)
114 BUG_ON(pipe1 == pipe2);
117 pipe_lock_nested(pipe1, I_MUTEX_PARENT);
118 pipe_lock_nested(pipe2, I_MUTEX_CHILD);
120 pipe_lock_nested(pipe2, I_MUTEX_PARENT);
121 pipe_lock_nested(pipe1, I_MUTEX_CHILD);
125 static void anon_pipe_buf_release(struct pipe_inode_info *pipe,
126 struct pipe_buffer *buf)
128 struct page *page = buf->page;
131 * If nobody else uses this page, and we don't already have a
132 * temporary page, let's keep track of it as a one-deep
133 * allocation cache. (Otherwise just release our reference to it)
135 if (page_count(page) == 1 && !pipe->tmp_page)
136 pipe->tmp_page = page;
141 static bool anon_pipe_buf_try_steal(struct pipe_inode_info *pipe,
142 struct pipe_buffer *buf)
144 struct page *page = buf->page;
146 if (page_count(page) != 1)
148 memcg_kmem_uncharge_page(page, 0);
149 __SetPageLocked(page);
154 * generic_pipe_buf_try_steal - attempt to take ownership of a &pipe_buffer
155 * @pipe: the pipe that the buffer belongs to
156 * @buf: the buffer to attempt to steal
159 * This function attempts to steal the &struct page attached to
160 * @buf. If successful, this function returns 0 and returns with
161 * the page locked. The caller may then reuse the page for whatever
162 * he wishes; the typical use is insertion into a different file
165 bool generic_pipe_buf_try_steal(struct pipe_inode_info *pipe,
166 struct pipe_buffer *buf)
168 struct page *page = buf->page;
171 * A reference of one is golden, that means that the owner of this
172 * page is the only one holding a reference to it. lock the page
175 if (page_count(page) == 1) {
181 EXPORT_SYMBOL(generic_pipe_buf_try_steal);
184 * generic_pipe_buf_get - get a reference to a &struct pipe_buffer
185 * @pipe: the pipe that the buffer belongs to
186 * @buf: the buffer to get a reference to
189 * This function grabs an extra reference to @buf. It's used in
190 * the tee() system call, when we duplicate the buffers in one
193 bool generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
195 return try_get_page(buf->page);
197 EXPORT_SYMBOL(generic_pipe_buf_get);
200 * generic_pipe_buf_release - put a reference to a &struct pipe_buffer
201 * @pipe: the pipe that the buffer belongs to
202 * @buf: the buffer to put a reference to
205 * This function releases a reference to @buf.
207 void generic_pipe_buf_release(struct pipe_inode_info *pipe,
208 struct pipe_buffer *buf)
212 EXPORT_SYMBOL(generic_pipe_buf_release);
214 static const struct pipe_buf_operations anon_pipe_buf_ops = {
215 .release = anon_pipe_buf_release,
216 .try_steal = anon_pipe_buf_try_steal,
217 .get = generic_pipe_buf_get,
220 /* Done while waiting without holding the pipe lock - thus the READ_ONCE() */
221 static inline bool pipe_readable(const struct pipe_inode_info *pipe)
223 unsigned int head = READ_ONCE(pipe->head);
224 unsigned int tail = READ_ONCE(pipe->tail);
225 unsigned int writers = READ_ONCE(pipe->writers);
227 return !pipe_empty(head, tail) || !writers;
230 static inline unsigned int pipe_update_tail(struct pipe_inode_info *pipe,
231 struct pipe_buffer *buf,
234 pipe_buf_release(pipe, buf);
237 * If the pipe has a watch_queue, we need additional protection
238 * by the spinlock because notifications get posted with only
239 * this spinlock, no mutex
241 if (pipe_has_watch_queue(pipe)) {
242 spin_lock_irq(&pipe->rd_wait.lock);
243 #ifdef CONFIG_WATCH_QUEUE
244 if (buf->flags & PIPE_BUF_FLAG_LOSS)
245 pipe->note_loss = true;
248 spin_unlock_irq(&pipe->rd_wait.lock);
253 * Without a watch_queue, we can simply increment the tail
254 * without the spinlock - the mutex is enough.
261 pipe_read(struct kiocb *iocb, struct iov_iter *to)
263 size_t total_len = iov_iter_count(to);
264 struct file *filp = iocb->ki_filp;
265 struct pipe_inode_info *pipe = filp->private_data;
266 bool was_full, wake_next_reader = false;
269 /* Null read succeeds. */
270 if (unlikely(total_len == 0))
277 * We only wake up writers if the pipe was full when we started
278 * reading in order to avoid unnecessary wakeups.
280 * But when we do wake up writers, we do so using a sync wakeup
281 * (WF_SYNC), because we want them to get going and generate more
284 was_full = pipe_full(pipe->head, pipe->tail, pipe->max_usage);
286 /* Read ->head with a barrier vs post_one_notification() */
287 unsigned int head = smp_load_acquire(&pipe->head);
288 unsigned int tail = pipe->tail;
289 unsigned int mask = pipe->ring_size - 1;
291 #ifdef CONFIG_WATCH_QUEUE
292 if (pipe->note_loss) {
293 struct watch_notification n;
301 n.type = WATCH_TYPE_META;
302 n.subtype = WATCH_META_LOSS_NOTIFICATION;
303 n.info = watch_sizeof(n);
304 if (copy_to_iter(&n, sizeof(n), to) != sizeof(n)) {
310 total_len -= sizeof(n);
311 pipe->note_loss = false;
315 if (!pipe_empty(head, tail)) {
316 struct pipe_buffer *buf = &pipe->bufs[tail & mask];
317 size_t chars = buf->len;
321 if (chars > total_len) {
322 if (buf->flags & PIPE_BUF_FLAG_WHOLE) {
330 error = pipe_buf_confirm(pipe, buf);
337 written = copy_page_to_iter(buf->page, buf->offset, chars, to);
338 if (unlikely(written < chars)) {
344 buf->offset += chars;
347 /* Was it a packet buffer? Clean up and exit */
348 if (buf->flags & PIPE_BUF_FLAG_PACKET) {
354 tail = pipe_update_tail(pipe, buf, tail);
357 break; /* common path: read succeeded */
358 if (!pipe_empty(head, tail)) /* More to do? */
366 if ((filp->f_flags & O_NONBLOCK) ||
367 (iocb->ki_flags & IOCB_NOWAIT)) {
374 * We only get here if we didn't actually read anything.
376 * However, we could have seen (and removed) a zero-sized
377 * pipe buffer, and might have made space in the buffers
380 * You can't make zero-sized pipe buffers by doing an empty
381 * write (not even in packet mode), but they can happen if
382 * the writer gets an EFAULT when trying to fill a buffer
383 * that already got allocated and inserted in the buffer
386 * So we still need to wake up any pending writers in the
387 * _very_ unlikely case that the pipe was full, but we got
390 if (unlikely(was_full))
391 wake_up_interruptible_sync_poll(&pipe->wr_wait, EPOLLOUT | EPOLLWRNORM);
392 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
395 * But because we didn't read anything, at this point we can
396 * just return directly with -ERESTARTSYS if we're interrupted,
397 * since we've done any required wakeups and there's no need
398 * to mark anything accessed. And we've dropped the lock.
400 if (wait_event_interruptible_exclusive(pipe->rd_wait, pipe_readable(pipe)) < 0)
404 was_full = pipe_full(pipe->head, pipe->tail, pipe->max_usage);
405 wake_next_reader = true;
407 if (pipe_empty(pipe->head, pipe->tail))
408 wake_next_reader = false;
412 wake_up_interruptible_sync_poll(&pipe->wr_wait, EPOLLOUT | EPOLLWRNORM);
413 if (wake_next_reader)
414 wake_up_interruptible_sync_poll(&pipe->rd_wait, EPOLLIN | EPOLLRDNORM);
415 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
421 static inline int is_packetized(struct file *file)
423 return (file->f_flags & O_DIRECT) != 0;
426 /* Done while waiting without holding the pipe lock - thus the READ_ONCE() */
427 static inline bool pipe_writable(const struct pipe_inode_info *pipe)
429 unsigned int head = READ_ONCE(pipe->head);
430 unsigned int tail = READ_ONCE(pipe->tail);
431 unsigned int max_usage = READ_ONCE(pipe->max_usage);
433 return !pipe_full(head, tail, max_usage) ||
434 !READ_ONCE(pipe->readers);
438 pipe_write(struct kiocb *iocb, struct iov_iter *from)
440 struct file *filp = iocb->ki_filp;
441 struct pipe_inode_info *pipe = filp->private_data;
444 size_t total_len = iov_iter_count(from);
446 bool was_empty = false;
447 bool wake_next_writer = false;
449 /* Null write succeeds. */
450 if (unlikely(total_len == 0))
455 if (!pipe->readers) {
456 send_sig(SIGPIPE, current, 0);
461 if (pipe_has_watch_queue(pipe)) {
467 * If it wasn't empty we try to merge new data into
470 * That naturally merges small writes, but it also
471 * page-aligns the rest of the writes for large writes
472 * spanning multiple pages.
475 was_empty = pipe_empty(head, pipe->tail);
476 chars = total_len & (PAGE_SIZE-1);
477 if (chars && !was_empty) {
478 unsigned int mask = pipe->ring_size - 1;
479 struct pipe_buffer *buf = &pipe->bufs[(head - 1) & mask];
480 int offset = buf->offset + buf->len;
482 if ((buf->flags & PIPE_BUF_FLAG_CAN_MERGE) &&
483 offset + chars <= PAGE_SIZE) {
484 ret = pipe_buf_confirm(pipe, buf);
488 ret = copy_page_from_iter(buf->page, offset, chars, from);
489 if (unlikely(ret < chars)) {
495 if (!iov_iter_count(from))
501 if (!pipe->readers) {
502 send_sig(SIGPIPE, current, 0);
509 if (!pipe_full(head, pipe->tail, pipe->max_usage)) {
510 unsigned int mask = pipe->ring_size - 1;
511 struct pipe_buffer *buf;
512 struct page *page = pipe->tmp_page;
516 page = alloc_page(GFP_HIGHUSER | __GFP_ACCOUNT);
517 if (unlikely(!page)) {
518 ret = ret ? : -ENOMEM;
521 pipe->tmp_page = page;
524 /* Allocate a slot in the ring in advance and attach an
525 * empty buffer. If we fault or otherwise fail to use
526 * it, either the reader will consume it or it'll still
527 * be there for the next write.
529 pipe->head = head + 1;
531 /* Insert it into the buffer array */
532 buf = &pipe->bufs[head & mask];
534 buf->ops = &anon_pipe_buf_ops;
537 if (is_packetized(filp))
538 buf->flags = PIPE_BUF_FLAG_PACKET;
540 buf->flags = PIPE_BUF_FLAG_CAN_MERGE;
541 pipe->tmp_page = NULL;
543 copied = copy_page_from_iter(page, 0, PAGE_SIZE, from);
544 if (unlikely(copied < PAGE_SIZE && iov_iter_count(from))) {
552 if (!iov_iter_count(from))
556 if (!pipe_full(head, pipe->tail, pipe->max_usage))
559 /* Wait for buffer space to become available. */
560 if ((filp->f_flags & O_NONBLOCK) ||
561 (iocb->ki_flags & IOCB_NOWAIT)) {
566 if (signal_pending(current)) {
573 * We're going to release the pipe lock and wait for more
574 * space. We wake up any readers if necessary, and then
575 * after waiting we need to re-check whether the pipe
576 * become empty while we dropped the lock.
580 wake_up_interruptible_sync_poll(&pipe->rd_wait, EPOLLIN | EPOLLRDNORM);
581 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
582 wait_event_interruptible_exclusive(pipe->wr_wait, pipe_writable(pipe));
584 was_empty = pipe_empty(pipe->head, pipe->tail);
585 wake_next_writer = true;
588 if (pipe_full(pipe->head, pipe->tail, pipe->max_usage))
589 wake_next_writer = false;
593 * If we do do a wakeup event, we do a 'sync' wakeup, because we
594 * want the reader to start processing things asap, rather than
595 * leave the data pending.
597 * This is particularly important for small writes, because of
598 * how (for example) the GNU make jobserver uses small writes to
599 * wake up pending jobs
601 * Epoll nonsensically wants a wakeup whether the pipe
602 * was already empty or not.
604 if (was_empty || pipe->poll_usage)
605 wake_up_interruptible_sync_poll(&pipe->rd_wait, EPOLLIN | EPOLLRDNORM);
606 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
607 if (wake_next_writer)
608 wake_up_interruptible_sync_poll(&pipe->wr_wait, EPOLLOUT | EPOLLWRNORM);
609 if (ret > 0 && sb_start_write_trylock(file_inode(filp)->i_sb)) {
610 int err = file_update_time(filp);
613 sb_end_write(file_inode(filp)->i_sb);
618 static long pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
620 struct pipe_inode_info *pipe = filp->private_data;
621 unsigned int count, head, tail, mask;
629 mask = pipe->ring_size - 1;
631 while (tail != head) {
632 count += pipe->bufs[tail & mask].len;
637 return put_user(count, (int __user *)arg);
639 #ifdef CONFIG_WATCH_QUEUE
640 case IOC_WATCH_QUEUE_SET_SIZE: {
643 ret = watch_queue_set_size(pipe, arg);
648 case IOC_WATCH_QUEUE_SET_FILTER:
649 return watch_queue_set_filter(
650 pipe, (struct watch_notification_filter __user *)arg);
658 /* No kernel lock held - fine */
660 pipe_poll(struct file *filp, poll_table *wait)
663 struct pipe_inode_info *pipe = filp->private_data;
664 unsigned int head, tail;
666 /* Epoll has some historical nasty semantics, this enables them */
667 WRITE_ONCE(pipe->poll_usage, true);
670 * Reading pipe state only -- no need for acquiring the semaphore.
672 * But because this is racy, the code has to add the
673 * entry to the poll table _first_ ..
675 if (filp->f_mode & FMODE_READ)
676 poll_wait(filp, &pipe->rd_wait, wait);
677 if (filp->f_mode & FMODE_WRITE)
678 poll_wait(filp, &pipe->wr_wait, wait);
681 * .. and only then can you do the racy tests. That way,
682 * if something changes and you got it wrong, the poll
683 * table entry will wake you up and fix it.
685 head = READ_ONCE(pipe->head);
686 tail = READ_ONCE(pipe->tail);
689 if (filp->f_mode & FMODE_READ) {
690 if (!pipe_empty(head, tail))
691 mask |= EPOLLIN | EPOLLRDNORM;
692 if (!pipe->writers && filp->f_version != pipe->w_counter)
696 if (filp->f_mode & FMODE_WRITE) {
697 if (!pipe_full(head, tail, pipe->max_usage))
698 mask |= EPOLLOUT | EPOLLWRNORM;
700 * Most Unices do not set EPOLLERR for FIFOs but on Linux they
701 * behave exactly like pipes for poll().
710 static void put_pipe_info(struct inode *inode, struct pipe_inode_info *pipe)
714 spin_lock(&inode->i_lock);
715 if (!--pipe->files) {
716 inode->i_pipe = NULL;
719 spin_unlock(&inode->i_lock);
722 free_pipe_info(pipe);
726 pipe_release(struct inode *inode, struct file *file)
728 struct pipe_inode_info *pipe = file->private_data;
731 if (file->f_mode & FMODE_READ)
733 if (file->f_mode & FMODE_WRITE)
736 /* Was that the last reader or writer, but not the other side? */
737 if (!pipe->readers != !pipe->writers) {
738 wake_up_interruptible_all(&pipe->rd_wait);
739 wake_up_interruptible_all(&pipe->wr_wait);
740 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
741 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
745 put_pipe_info(inode, pipe);
750 pipe_fasync(int fd, struct file *filp, int on)
752 struct pipe_inode_info *pipe = filp->private_data;
756 if (filp->f_mode & FMODE_READ)
757 retval = fasync_helper(fd, filp, on, &pipe->fasync_readers);
758 if ((filp->f_mode & FMODE_WRITE) && retval >= 0) {
759 retval = fasync_helper(fd, filp, on, &pipe->fasync_writers);
760 if (retval < 0 && (filp->f_mode & FMODE_READ))
761 /* this can happen only if on == T */
762 fasync_helper(-1, filp, 0, &pipe->fasync_readers);
768 unsigned long account_pipe_buffers(struct user_struct *user,
769 unsigned long old, unsigned long new)
771 return atomic_long_add_return(new - old, &user->pipe_bufs);
774 bool too_many_pipe_buffers_soft(unsigned long user_bufs)
776 unsigned long soft_limit = READ_ONCE(pipe_user_pages_soft);
778 return soft_limit && user_bufs > soft_limit;
781 bool too_many_pipe_buffers_hard(unsigned long user_bufs)
783 unsigned long hard_limit = READ_ONCE(pipe_user_pages_hard);
785 return hard_limit && user_bufs > hard_limit;
788 bool pipe_is_unprivileged_user(void)
790 return !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN);
793 struct pipe_inode_info *alloc_pipe_info(void)
795 struct pipe_inode_info *pipe;
796 unsigned long pipe_bufs = PIPE_DEF_BUFFERS;
797 struct user_struct *user = get_current_user();
798 unsigned long user_bufs;
799 unsigned int max_size = READ_ONCE(pipe_max_size);
801 pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL_ACCOUNT);
805 if (pipe_bufs * PAGE_SIZE > max_size && !capable(CAP_SYS_RESOURCE))
806 pipe_bufs = max_size >> PAGE_SHIFT;
808 user_bufs = account_pipe_buffers(user, 0, pipe_bufs);
810 if (too_many_pipe_buffers_soft(user_bufs) && pipe_is_unprivileged_user()) {
811 user_bufs = account_pipe_buffers(user, pipe_bufs, PIPE_MIN_DEF_BUFFERS);
812 pipe_bufs = PIPE_MIN_DEF_BUFFERS;
815 if (too_many_pipe_buffers_hard(user_bufs) && pipe_is_unprivileged_user())
816 goto out_revert_acct;
818 pipe->bufs = kcalloc(pipe_bufs, sizeof(struct pipe_buffer),
822 init_waitqueue_head(&pipe->rd_wait);
823 init_waitqueue_head(&pipe->wr_wait);
824 pipe->r_counter = pipe->w_counter = 1;
825 pipe->max_usage = pipe_bufs;
826 pipe->ring_size = pipe_bufs;
827 pipe->nr_accounted = pipe_bufs;
829 mutex_init(&pipe->mutex);
834 (void) account_pipe_buffers(user, pipe_bufs, 0);
841 void free_pipe_info(struct pipe_inode_info *pipe)
845 #ifdef CONFIG_WATCH_QUEUE
846 if (pipe->watch_queue)
847 watch_queue_clear(pipe->watch_queue);
850 (void) account_pipe_buffers(pipe->user, pipe->nr_accounted, 0);
851 free_uid(pipe->user);
852 for (i = 0; i < pipe->ring_size; i++) {
853 struct pipe_buffer *buf = pipe->bufs + i;
855 pipe_buf_release(pipe, buf);
857 #ifdef CONFIG_WATCH_QUEUE
858 if (pipe->watch_queue)
859 put_watch_queue(pipe->watch_queue);
862 __free_page(pipe->tmp_page);
867 static struct vfsmount *pipe_mnt __ro_after_init;
870 * pipefs_dname() is called from d_path().
872 static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen)
874 return dynamic_dname(buffer, buflen, "pipe:[%lu]",
875 d_inode(dentry)->i_ino);
878 static const struct dentry_operations pipefs_dentry_operations = {
879 .d_dname = pipefs_dname,
882 static struct inode * get_pipe_inode(void)
884 struct inode *inode = new_inode_pseudo(pipe_mnt->mnt_sb);
885 struct pipe_inode_info *pipe;
890 inode->i_ino = get_next_ino();
892 pipe = alloc_pipe_info();
896 inode->i_pipe = pipe;
898 pipe->readers = pipe->writers = 1;
899 inode->i_fop = &pipefifo_fops;
902 * Mark the inode dirty from the very beginning,
903 * that way it will never be moved to the dirty
904 * list because "mark_inode_dirty()" will think
905 * that it already _is_ on the dirty list.
907 inode->i_state = I_DIRTY;
908 inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR;
909 inode->i_uid = current_fsuid();
910 inode->i_gid = current_fsgid();
911 simple_inode_init_ts(inode);
922 int create_pipe_files(struct file **res, int flags)
924 struct inode *inode = get_pipe_inode();
931 if (flags & O_NOTIFICATION_PIPE) {
932 error = watch_queue_init(inode->i_pipe);
934 free_pipe_info(inode->i_pipe);
940 f = alloc_file_pseudo(inode, pipe_mnt, "",
941 O_WRONLY | (flags & (O_NONBLOCK | O_DIRECT)),
944 free_pipe_info(inode->i_pipe);
949 f->private_data = inode->i_pipe;
951 res[0] = alloc_file_clone(f, O_RDONLY | (flags & O_NONBLOCK),
953 if (IS_ERR(res[0])) {
954 put_pipe_info(inode, inode->i_pipe);
956 return PTR_ERR(res[0]);
958 res[0]->private_data = inode->i_pipe;
960 stream_open(inode, res[0]);
961 stream_open(inode, res[1]);
965 static int __do_pipe_flags(int *fd, struct file **files, int flags)
970 if (flags & ~(O_CLOEXEC | O_NONBLOCK | O_DIRECT | O_NOTIFICATION_PIPE))
973 error = create_pipe_files(files, flags);
977 error = get_unused_fd_flags(flags);
982 error = get_unused_fd_flags(flags);
987 audit_fd_pair(fdr, fdw);
990 /* pipe groks IOCB_NOWAIT */
991 files[0]->f_mode |= FMODE_NOWAIT;
992 files[1]->f_mode |= FMODE_NOWAIT;
1003 int do_pipe_flags(int *fd, int flags)
1005 struct file *files[2];
1006 int error = __do_pipe_flags(fd, files, flags);
1008 fd_install(fd[0], files[0]);
1009 fd_install(fd[1], files[1]);
1015 * sys_pipe() is the normal C calling standard for creating
1016 * a pipe. It's not the way Unix traditionally does this, though.
1018 static int do_pipe2(int __user *fildes, int flags)
1020 struct file *files[2];
1024 error = __do_pipe_flags(fd, files, flags);
1026 if (unlikely(copy_to_user(fildes, fd, sizeof(fd)))) {
1029 put_unused_fd(fd[0]);
1030 put_unused_fd(fd[1]);
1033 fd_install(fd[0], files[0]);
1034 fd_install(fd[1], files[1]);
1040 SYSCALL_DEFINE2(pipe2, int __user *, fildes, int, flags)
1042 return do_pipe2(fildes, flags);
1045 SYSCALL_DEFINE1(pipe, int __user *, fildes)
1047 return do_pipe2(fildes, 0);
1051 * This is the stupid "wait for pipe to be readable or writable"
1054 * See pipe_read/write() for the proper kind of exclusive wait,
1055 * but that requires that we wake up any other readers/writers
1056 * if we then do not end up reading everything (ie the whole
1057 * "wake_next_reader/writer" logic in pipe_read/write()).
1059 void pipe_wait_readable(struct pipe_inode_info *pipe)
1062 wait_event_interruptible(pipe->rd_wait, pipe_readable(pipe));
1066 void pipe_wait_writable(struct pipe_inode_info *pipe)
1069 wait_event_interruptible(pipe->wr_wait, pipe_writable(pipe));
1074 * This depends on both the wait (here) and the wakeup (wake_up_partner)
1075 * holding the pipe lock, so "*cnt" is stable and we know a wakeup cannot
1076 * race with the count check and waitqueue prep.
1078 * Normally in order to avoid races, you'd do the prepare_to_wait() first,
1079 * then check the condition you're waiting for, and only then sleep. But
1080 * because of the pipe lock, we can check the condition before being on
1083 * We use the 'rd_wait' waitqueue for pipe partner waiting.
1085 static int wait_for_partner(struct pipe_inode_info *pipe, unsigned int *cnt)
1087 DEFINE_WAIT(rdwait);
1090 while (cur == *cnt) {
1091 prepare_to_wait(&pipe->rd_wait, &rdwait, TASK_INTERRUPTIBLE);
1094 finish_wait(&pipe->rd_wait, &rdwait);
1096 if (signal_pending(current))
1099 return cur == *cnt ? -ERESTARTSYS : 0;
1102 static void wake_up_partner(struct pipe_inode_info *pipe)
1104 wake_up_interruptible_all(&pipe->rd_wait);
1107 static int fifo_open(struct inode *inode, struct file *filp)
1109 struct pipe_inode_info *pipe;
1110 bool is_pipe = inode->i_sb->s_magic == PIPEFS_MAGIC;
1113 filp->f_version = 0;
1115 spin_lock(&inode->i_lock);
1116 if (inode->i_pipe) {
1117 pipe = inode->i_pipe;
1119 spin_unlock(&inode->i_lock);
1121 spin_unlock(&inode->i_lock);
1122 pipe = alloc_pipe_info();
1126 spin_lock(&inode->i_lock);
1127 if (unlikely(inode->i_pipe)) {
1128 inode->i_pipe->files++;
1129 spin_unlock(&inode->i_lock);
1130 free_pipe_info(pipe);
1131 pipe = inode->i_pipe;
1133 inode->i_pipe = pipe;
1134 spin_unlock(&inode->i_lock);
1137 filp->private_data = pipe;
1138 /* OK, we have a pipe and it's pinned down */
1142 /* We can only do regular read/write on fifos */
1143 stream_open(inode, filp);
1145 switch (filp->f_mode & (FMODE_READ | FMODE_WRITE)) {
1149 * POSIX.1 says that O_NONBLOCK means return with the FIFO
1150 * opened, even when there is no process writing the FIFO.
1153 if (pipe->readers++ == 0)
1154 wake_up_partner(pipe);
1156 if (!is_pipe && !pipe->writers) {
1157 if ((filp->f_flags & O_NONBLOCK)) {
1158 /* suppress EPOLLHUP until we have
1160 filp->f_version = pipe->w_counter;
1162 if (wait_for_partner(pipe, &pipe->w_counter))
1171 * POSIX.1 says that O_NONBLOCK means return -1 with
1172 * errno=ENXIO when there is no process reading the FIFO.
1175 if (!is_pipe && (filp->f_flags & O_NONBLOCK) && !pipe->readers)
1179 if (!pipe->writers++)
1180 wake_up_partner(pipe);
1182 if (!is_pipe && !pipe->readers) {
1183 if (wait_for_partner(pipe, &pipe->r_counter))
1188 case FMODE_READ | FMODE_WRITE:
1191 * POSIX.1 leaves this case "undefined" when O_NONBLOCK is set.
1192 * This implementation will NEVER block on a O_RDWR open, since
1193 * the process can at least talk to itself.
1200 if (pipe->readers == 1 || pipe->writers == 1)
1201 wake_up_partner(pipe);
1210 __pipe_unlock(pipe);
1214 if (!--pipe->readers)
1215 wake_up_interruptible(&pipe->wr_wait);
1220 if (!--pipe->writers)
1221 wake_up_interruptible_all(&pipe->rd_wait);
1226 __pipe_unlock(pipe);
1228 put_pipe_info(inode, pipe);
1232 const struct file_operations pipefifo_fops = {
1234 .llseek = no_llseek,
1235 .read_iter = pipe_read,
1236 .write_iter = pipe_write,
1238 .unlocked_ioctl = pipe_ioctl,
1239 .release = pipe_release,
1240 .fasync = pipe_fasync,
1241 .splice_write = iter_file_splice_write,
1245 * Currently we rely on the pipe array holding a power-of-2 number
1246 * of pages. Returns 0 on error.
1248 unsigned int round_pipe_size(unsigned int size)
1250 if (size > (1U << 31))
1253 /* Minimum pipe size, as required by POSIX */
1254 if (size < PAGE_SIZE)
1257 return roundup_pow_of_two(size);
1261 * Resize the pipe ring to a number of slots.
1263 * Note the pipe can be reduced in capacity, but only if the current
1264 * occupancy doesn't exceed nr_slots; if it does, EBUSY will be
1267 int pipe_resize_ring(struct pipe_inode_info *pipe, unsigned int nr_slots)
1269 struct pipe_buffer *bufs;
1270 unsigned int head, tail, mask, n;
1272 bufs = kcalloc(nr_slots, sizeof(*bufs),
1273 GFP_KERNEL_ACCOUNT | __GFP_NOWARN);
1274 if (unlikely(!bufs))
1277 spin_lock_irq(&pipe->rd_wait.lock);
1278 mask = pipe->ring_size - 1;
1282 n = pipe_occupancy(head, tail);
1284 spin_unlock_irq(&pipe->rd_wait.lock);
1290 * The pipe array wraps around, so just start the new one at zero
1291 * and adjust the indices.
1294 unsigned int h = head & mask;
1295 unsigned int t = tail & mask;
1297 memcpy(bufs, pipe->bufs + t,
1298 n * sizeof(struct pipe_buffer));
1300 unsigned int tsize = pipe->ring_size - t;
1302 memcpy(bufs + tsize, pipe->bufs,
1303 h * sizeof(struct pipe_buffer));
1304 memcpy(bufs, pipe->bufs + t,
1305 tsize * sizeof(struct pipe_buffer));
1314 pipe->ring_size = nr_slots;
1315 if (pipe->max_usage > nr_slots)
1316 pipe->max_usage = nr_slots;
1320 spin_unlock_irq(&pipe->rd_wait.lock);
1322 /* This might have made more room for writers */
1323 wake_up_interruptible(&pipe->wr_wait);
1328 * Allocate a new array of pipe buffers and copy the info over. Returns the
1329 * pipe size if successful, or return -ERROR on error.
1331 static long pipe_set_size(struct pipe_inode_info *pipe, unsigned int arg)
1333 unsigned long user_bufs;
1334 unsigned int nr_slots, size;
1337 if (pipe_has_watch_queue(pipe))
1340 size = round_pipe_size(arg);
1341 nr_slots = size >> PAGE_SHIFT;
1347 * If trying to increase the pipe capacity, check that an
1348 * unprivileged user is not trying to exceed various limits
1349 * (soft limit check here, hard limit check just below).
1350 * Decreasing the pipe capacity is always permitted, even
1351 * if the user is currently over a limit.
1353 if (nr_slots > pipe->max_usage &&
1354 size > pipe_max_size && !capable(CAP_SYS_RESOURCE))
1357 user_bufs = account_pipe_buffers(pipe->user, pipe->nr_accounted, nr_slots);
1359 if (nr_slots > pipe->max_usage &&
1360 (too_many_pipe_buffers_hard(user_bufs) ||
1361 too_many_pipe_buffers_soft(user_bufs)) &&
1362 pipe_is_unprivileged_user()) {
1364 goto out_revert_acct;
1367 ret = pipe_resize_ring(pipe, nr_slots);
1369 goto out_revert_acct;
1371 pipe->max_usage = nr_slots;
1372 pipe->nr_accounted = nr_slots;
1373 return pipe->max_usage * PAGE_SIZE;
1376 (void) account_pipe_buffers(pipe->user, nr_slots, pipe->nr_accounted);
1381 * Note that i_pipe and i_cdev share the same location, so checking ->i_pipe is
1382 * not enough to verify that this is a pipe.
1384 struct pipe_inode_info *get_pipe_info(struct file *file, bool for_splice)
1386 struct pipe_inode_info *pipe = file->private_data;
1388 if (file->f_op != &pipefifo_fops || !pipe)
1390 if (for_splice && pipe_has_watch_queue(pipe))
1395 long pipe_fcntl(struct file *file, unsigned int cmd, unsigned int arg)
1397 struct pipe_inode_info *pipe;
1400 pipe = get_pipe_info(file, false);
1408 ret = pipe_set_size(pipe, arg);
1411 ret = pipe->max_usage * PAGE_SIZE;
1418 __pipe_unlock(pipe);
1422 static const struct super_operations pipefs_ops = {
1423 .destroy_inode = free_inode_nonrcu,
1424 .statfs = simple_statfs,
1428 * pipefs should _never_ be mounted by userland - too much of security hassle,
1429 * no real gain from having the whole whorehouse mounted. So we don't need
1430 * any operations on the root directory. However, we need a non-trivial
1431 * d_name - pipe: will go nicely and kill the special-casing in procfs.
1434 static int pipefs_init_fs_context(struct fs_context *fc)
1436 struct pseudo_fs_context *ctx = init_pseudo(fc, PIPEFS_MAGIC);
1439 ctx->ops = &pipefs_ops;
1440 ctx->dops = &pipefs_dentry_operations;
1444 static struct file_system_type pipe_fs_type = {
1446 .init_fs_context = pipefs_init_fs_context,
1447 .kill_sb = kill_anon_super,
1450 #ifdef CONFIG_SYSCTL
1451 static int do_proc_dopipe_max_size_conv(unsigned long *lvalp,
1453 int write, void *data)
1458 val = round_pipe_size(*lvalp);
1464 unsigned int val = *valp;
1465 *lvalp = (unsigned long) val;
1471 static int proc_dopipe_max_size(struct ctl_table *table, int write,
1472 void *buffer, size_t *lenp, loff_t *ppos)
1474 return do_proc_douintvec(table, write, buffer, lenp, ppos,
1475 do_proc_dopipe_max_size_conv, NULL);
1478 static struct ctl_table fs_pipe_sysctls[] = {
1480 .procname = "pipe-max-size",
1481 .data = &pipe_max_size,
1482 .maxlen = sizeof(pipe_max_size),
1484 .proc_handler = proc_dopipe_max_size,
1487 .procname = "pipe-user-pages-hard",
1488 .data = &pipe_user_pages_hard,
1489 .maxlen = sizeof(pipe_user_pages_hard),
1491 .proc_handler = proc_doulongvec_minmax,
1494 .procname = "pipe-user-pages-soft",
1495 .data = &pipe_user_pages_soft,
1496 .maxlen = sizeof(pipe_user_pages_soft),
1498 .proc_handler = proc_doulongvec_minmax,
1504 static int __init init_pipe_fs(void)
1506 int err = register_filesystem(&pipe_fs_type);
1509 pipe_mnt = kern_mount(&pipe_fs_type);
1510 if (IS_ERR(pipe_mnt)) {
1511 err = PTR_ERR(pipe_mnt);
1512 unregister_filesystem(&pipe_fs_type);
1515 #ifdef CONFIG_SYSCTL
1516 register_sysctl_init("fs", fs_pipe_sysctls);
1521 fs_initcall(init_pipe_fs);