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/magic.h>
18 #include <linux/pipe_fs_i.h>
19 #include <linux/uio.h>
20 #include <linux/highmem.h>
21 #include <linux/pagemap.h>
22 #include <linux/audit.h>
23 #include <linux/syscalls.h>
24 #include <linux/fcntl.h>
25 #include <linux/memcontrol.h>
27 #include <linux/uaccess.h>
28 #include <asm/ioctls.h>
33 * New pipe buffers will be restricted to this size while the user is exceeding
34 * their pipe buffer quota. The general pipe use case needs at least two
35 * buffers: one for data yet to be read, and one for new data. If this is less
36 * than two, then a write to a non-empty pipe may block even if the pipe is not
37 * full. This can occur with GNU make jobserver or similar uses of pipes as
38 * semaphores: multiple processes may be waiting to write tokens back to the
39 * pipe before reading tokens: https://lore.kernel.org/lkml/1628086770.5rn8p04n6j.none@localhost/.
41 * Users can reduce their pipe buffers with F_SETPIPE_SZ below this at their
42 * own risk, namely: pipe writes to non-full pipes may block until the pipe is
45 #define PIPE_MIN_DEF_BUFFERS 2
48 * The max size that a non-root user is allowed to grow the pipe. Can
49 * be set by root in /proc/sys/fs/pipe-max-size
51 unsigned int pipe_max_size = 1048576;
54 * Minimum pipe size, as required by POSIX
56 unsigned int pipe_min_size = PAGE_SIZE;
58 /* Maximum allocatable pages per user. Hard limit is unset by default, soft
59 * matches default values.
61 unsigned long pipe_user_pages_hard;
62 unsigned long pipe_user_pages_soft = PIPE_DEF_BUFFERS * INR_OPEN_CUR;
65 * We use a start+len construction, which provides full use of the
67 * -- Florian Coosmann (FGC)
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 /* Drop the inode semaphore and wait for a pipe event, atomically */
126 void pipe_wait(struct pipe_inode_info *pipe)
131 * Pipes are system-local resources, so sleeping on them
132 * is considered a noninteractive wait:
134 prepare_to_wait(&pipe->wait, &wait, TASK_INTERRUPTIBLE);
137 finish_wait(&pipe->wait, &wait);
141 static void anon_pipe_buf_release(struct pipe_inode_info *pipe,
142 struct pipe_buffer *buf)
144 struct page *page = buf->page;
147 * If nobody else uses this page, and we don't already have a
148 * temporary page, let's keep track of it as a one-deep
149 * allocation cache. (Otherwise just release our reference to it)
151 if (page_count(page) == 1 && !pipe->tmp_page)
152 pipe->tmp_page = page;
157 static int anon_pipe_buf_steal(struct pipe_inode_info *pipe,
158 struct pipe_buffer *buf)
160 struct page *page = buf->page;
162 if (page_count(page) == 1) {
163 if (memcg_kmem_enabled())
164 memcg_kmem_uncharge(page, 0);
165 __SetPageLocked(page);
172 * generic_pipe_buf_steal - attempt to take ownership of a &pipe_buffer
173 * @pipe: the pipe that the buffer belongs to
174 * @buf: the buffer to attempt to steal
177 * This function attempts to steal the &struct page attached to
178 * @buf. If successful, this function returns 0 and returns with
179 * the page locked. The caller may then reuse the page for whatever
180 * he wishes; the typical use is insertion into a different file
183 int generic_pipe_buf_steal(struct pipe_inode_info *pipe,
184 struct pipe_buffer *buf)
186 struct page *page = buf->page;
189 * A reference of one is golden, that means that the owner of this
190 * page is the only one holding a reference to it. lock the page
193 if (page_count(page) == 1) {
200 EXPORT_SYMBOL(generic_pipe_buf_steal);
203 * generic_pipe_buf_get - get a reference to a &struct pipe_buffer
204 * @pipe: the pipe that the buffer belongs to
205 * @buf: the buffer to get a reference to
208 * This function grabs an extra reference to @buf. It's used in
209 * in the tee() system call, when we duplicate the buffers in one
212 bool generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
214 return try_get_page(buf->page);
216 EXPORT_SYMBOL(generic_pipe_buf_get);
219 * generic_pipe_buf_confirm - verify contents of the pipe buffer
220 * @info: the pipe that the buffer belongs to
221 * @buf: the buffer to confirm
224 * This function does nothing, because the generic pipe code uses
225 * pages that are always good when inserted into the pipe.
227 int generic_pipe_buf_confirm(struct pipe_inode_info *info,
228 struct pipe_buffer *buf)
232 EXPORT_SYMBOL(generic_pipe_buf_confirm);
235 * generic_pipe_buf_release - put a reference to a &struct pipe_buffer
236 * @pipe: the pipe that the buffer belongs to
237 * @buf: the buffer to put a reference to
240 * This function releases a reference to @buf.
242 void generic_pipe_buf_release(struct pipe_inode_info *pipe,
243 struct pipe_buffer *buf)
247 EXPORT_SYMBOL(generic_pipe_buf_release);
249 static const struct pipe_buf_operations anon_pipe_buf_ops = {
251 .confirm = generic_pipe_buf_confirm,
252 .release = anon_pipe_buf_release,
253 .steal = anon_pipe_buf_steal,
254 .get = generic_pipe_buf_get,
257 static const struct pipe_buf_operations anon_pipe_buf_nomerge_ops = {
259 .confirm = generic_pipe_buf_confirm,
260 .release = anon_pipe_buf_release,
261 .steal = anon_pipe_buf_steal,
262 .get = generic_pipe_buf_get,
265 static const struct pipe_buf_operations packet_pipe_buf_ops = {
267 .confirm = generic_pipe_buf_confirm,
268 .release = anon_pipe_buf_release,
269 .steal = anon_pipe_buf_steal,
270 .get = generic_pipe_buf_get,
273 void pipe_buf_mark_unmergeable(struct pipe_buffer *buf)
275 if (buf->ops == &anon_pipe_buf_ops)
276 buf->ops = &anon_pipe_buf_nomerge_ops;
280 pipe_read(struct kiocb *iocb, struct iov_iter *to)
282 size_t total_len = iov_iter_count(to);
283 struct file *filp = iocb->ki_filp;
284 struct pipe_inode_info *pipe = filp->private_data;
288 /* Null read succeeds. */
289 if (unlikely(total_len == 0))
296 int bufs = pipe->nrbufs;
298 int curbuf = pipe->curbuf;
299 struct pipe_buffer *buf = pipe->bufs + curbuf;
300 size_t chars = buf->len;
304 if (chars > total_len)
307 error = pipe_buf_confirm(pipe, buf);
314 written = copy_page_to_iter(buf->page, buf->offset, chars, to);
315 if (unlikely(written < chars)) {
321 buf->offset += chars;
324 /* Was it a packet buffer? Clean up and exit */
325 if (buf->flags & PIPE_BUF_FLAG_PACKET) {
331 pipe_buf_release(pipe, buf);
332 curbuf = (curbuf + 1) & (pipe->buffers - 1);
333 pipe->curbuf = curbuf;
334 pipe->nrbufs = --bufs;
339 break; /* common path: read succeeded */
341 if (bufs) /* More to do? */
345 if (!pipe->waiting_writers) {
346 /* syscall merging: Usually we must not sleep
347 * if O_NONBLOCK is set, or if we got some data.
348 * But if a writer sleeps in kernel space, then
349 * we can wait for that data without violating POSIX.
353 if (filp->f_flags & O_NONBLOCK) {
358 if (signal_pending(current)) {
364 wake_up_interruptible_sync_poll(&pipe->wait, POLLOUT | POLLWRNORM);
365 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
371 /* Signal writers asynchronously that there is more room. */
373 wake_up_interruptible_sync_poll(&pipe->wait, POLLOUT | POLLWRNORM);
374 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
381 static inline int is_packetized(struct file *file)
383 return (file->f_flags & O_DIRECT) != 0;
387 pipe_write(struct kiocb *iocb, struct iov_iter *from)
389 struct file *filp = iocb->ki_filp;
390 struct pipe_inode_info *pipe = filp->private_data;
393 size_t total_len = iov_iter_count(from);
396 /* Null write succeeds. */
397 if (unlikely(total_len == 0))
402 if (!pipe->readers) {
403 send_sig(SIGPIPE, current, 0);
408 /* We try to merge small writes */
409 chars = total_len & (PAGE_SIZE-1); /* size of the last buffer */
410 if (pipe->nrbufs && chars != 0) {
411 int lastbuf = (pipe->curbuf + pipe->nrbufs - 1) &
413 struct pipe_buffer *buf = pipe->bufs + lastbuf;
414 int offset = buf->offset + buf->len;
416 if (buf->ops->can_merge && offset + chars <= PAGE_SIZE) {
417 ret = pipe_buf_confirm(pipe, buf);
421 ret = copy_page_from_iter(buf->page, offset, chars, from);
422 if (unlikely(ret < chars)) {
428 if (!iov_iter_count(from))
436 if (!pipe->readers) {
437 send_sig(SIGPIPE, current, 0);
443 if (bufs < pipe->buffers) {
444 int newbuf = (pipe->curbuf + bufs) & (pipe->buffers-1);
445 struct pipe_buffer *buf = pipe->bufs + newbuf;
446 struct page *page = pipe->tmp_page;
450 page = alloc_page(GFP_HIGHUSER | __GFP_ACCOUNT);
451 if (unlikely(!page)) {
452 ret = ret ? : -ENOMEM;
455 pipe->tmp_page = page;
457 /* Always wake up, even if the copy fails. Otherwise
458 * we lock up (O_NONBLOCK-)readers that sleep due to
460 * FIXME! Is this really true?
463 copied = copy_page_from_iter(page, 0, PAGE_SIZE, from);
464 if (unlikely(copied < PAGE_SIZE && iov_iter_count(from))) {
471 /* Insert it into the buffer array */
473 buf->ops = &anon_pipe_buf_ops;
477 if (is_packetized(filp)) {
478 buf->ops = &packet_pipe_buf_ops;
479 buf->flags = PIPE_BUF_FLAG_PACKET;
481 pipe->nrbufs = ++bufs;
482 pipe->tmp_page = NULL;
484 if (!iov_iter_count(from))
487 if (bufs < pipe->buffers)
489 if (filp->f_flags & O_NONBLOCK) {
494 if (signal_pending(current)) {
500 wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLRDNORM);
501 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
504 pipe->waiting_writers++;
506 pipe->waiting_writers--;
511 wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLRDNORM);
512 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
514 if (ret > 0 && sb_start_write_trylock(file_inode(filp)->i_sb)) {
515 int err = file_update_time(filp);
518 sb_end_write(file_inode(filp)->i_sb);
523 static long pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
525 struct pipe_inode_info *pipe = filp->private_data;
526 int count, buf, nrbufs;
533 nrbufs = pipe->nrbufs;
534 while (--nrbufs >= 0) {
535 count += pipe->bufs[buf].len;
536 buf = (buf+1) & (pipe->buffers - 1);
540 return put_user(count, (int __user *)arg);
546 /* No kernel lock held - fine */
548 pipe_poll(struct file *filp, poll_table *wait)
551 struct pipe_inode_info *pipe = filp->private_data;
554 poll_wait(filp, &pipe->wait, wait);
556 /* Reading only -- no need for acquiring the semaphore. */
557 nrbufs = pipe->nrbufs;
559 if (filp->f_mode & FMODE_READ) {
560 mask = (nrbufs > 0) ? POLLIN | POLLRDNORM : 0;
561 if (!pipe->writers && filp->f_version != pipe->w_counter)
565 if (filp->f_mode & FMODE_WRITE) {
566 mask |= (nrbufs < pipe->buffers) ? POLLOUT | POLLWRNORM : 0;
568 * Most Unices do not set POLLERR for FIFOs but on Linux they
569 * behave exactly like pipes for poll().
578 static void put_pipe_info(struct inode *inode, struct pipe_inode_info *pipe)
582 spin_lock(&inode->i_lock);
583 if (!--pipe->files) {
584 inode->i_pipe = NULL;
587 spin_unlock(&inode->i_lock);
590 free_pipe_info(pipe);
594 pipe_release(struct inode *inode, struct file *file)
596 struct pipe_inode_info *pipe = file->private_data;
599 if (file->f_mode & FMODE_READ)
601 if (file->f_mode & FMODE_WRITE)
604 if (pipe->readers || pipe->writers) {
605 wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLOUT | POLLRDNORM | POLLWRNORM | POLLERR | POLLHUP);
606 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
607 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
611 put_pipe_info(inode, pipe);
616 pipe_fasync(int fd, struct file *filp, int on)
618 struct pipe_inode_info *pipe = filp->private_data;
622 if (filp->f_mode & FMODE_READ)
623 retval = fasync_helper(fd, filp, on, &pipe->fasync_readers);
624 if ((filp->f_mode & FMODE_WRITE) && retval >= 0) {
625 retval = fasync_helper(fd, filp, on, &pipe->fasync_writers);
626 if (retval < 0 && (filp->f_mode & FMODE_READ))
627 /* this can happen only if on == T */
628 fasync_helper(-1, filp, 0, &pipe->fasync_readers);
634 static unsigned long account_pipe_buffers(struct user_struct *user,
635 unsigned long old, unsigned long new)
637 return atomic_long_add_return(new - old, &user->pipe_bufs);
640 static bool too_many_pipe_buffers_soft(unsigned long user_bufs)
642 return pipe_user_pages_soft && user_bufs > pipe_user_pages_soft;
645 static bool too_many_pipe_buffers_hard(unsigned long user_bufs)
647 return pipe_user_pages_hard && user_bufs > pipe_user_pages_hard;
650 static bool is_unprivileged_user(void)
652 return !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN);
655 struct pipe_inode_info *alloc_pipe_info(void)
657 struct pipe_inode_info *pipe;
658 unsigned long pipe_bufs = PIPE_DEF_BUFFERS;
659 struct user_struct *user = get_current_user();
660 unsigned long user_bufs;
662 pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL_ACCOUNT);
666 if (pipe_bufs * PAGE_SIZE > pipe_max_size && !capable(CAP_SYS_RESOURCE))
667 pipe_bufs = pipe_max_size >> PAGE_SHIFT;
669 user_bufs = account_pipe_buffers(user, 0, pipe_bufs);
671 if (too_many_pipe_buffers_soft(user_bufs) && is_unprivileged_user()) {
672 user_bufs = account_pipe_buffers(user, pipe_bufs, PIPE_MIN_DEF_BUFFERS);
673 pipe_bufs = PIPE_MIN_DEF_BUFFERS;
676 if (too_many_pipe_buffers_hard(user_bufs) && is_unprivileged_user())
677 goto out_revert_acct;
679 pipe->bufs = kcalloc(pipe_bufs, sizeof(struct pipe_buffer),
683 init_waitqueue_head(&pipe->wait);
684 pipe->r_counter = pipe->w_counter = 1;
685 pipe->buffers = pipe_bufs;
687 mutex_init(&pipe->mutex);
692 (void) account_pipe_buffers(user, pipe_bufs, 0);
699 void free_pipe_info(struct pipe_inode_info *pipe)
703 (void) account_pipe_buffers(pipe->user, pipe->buffers, 0);
704 free_uid(pipe->user);
705 for (i = 0; i < pipe->buffers; i++) {
706 struct pipe_buffer *buf = pipe->bufs + i;
708 pipe_buf_release(pipe, buf);
711 __free_page(pipe->tmp_page);
716 static struct vfsmount *pipe_mnt __read_mostly;
719 * pipefs_dname() is called from d_path().
721 static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen)
723 return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]",
724 d_inode(dentry)->i_ino);
727 static const struct dentry_operations pipefs_dentry_operations = {
728 .d_dname = pipefs_dname,
731 static struct inode * get_pipe_inode(void)
733 struct inode *inode = new_inode_pseudo(pipe_mnt->mnt_sb);
734 struct pipe_inode_info *pipe;
739 inode->i_ino = get_next_ino();
741 pipe = alloc_pipe_info();
745 inode->i_pipe = pipe;
747 pipe->readers = pipe->writers = 1;
748 inode->i_fop = &pipefifo_fops;
751 * Mark the inode dirty from the very beginning,
752 * that way it will never be moved to the dirty
753 * list because "mark_inode_dirty()" will think
754 * that it already _is_ on the dirty list.
756 inode->i_state = I_DIRTY;
757 inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR;
758 inode->i_uid = current_fsuid();
759 inode->i_gid = current_fsgid();
760 inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
771 int create_pipe_files(struct file **res, int flags)
774 struct inode *inode = get_pipe_inode();
782 path.dentry = d_alloc_pseudo(pipe_mnt->mnt_sb, &empty_name);
785 path.mnt = mntget(pipe_mnt);
787 d_instantiate(path.dentry, inode);
789 f = alloc_file(&path, FMODE_WRITE, &pipefifo_fops);
795 f->f_flags = O_WRONLY | (flags & (O_NONBLOCK | O_DIRECT));
796 f->private_data = inode->i_pipe;
798 res[0] = alloc_file(&path, FMODE_READ, &pipefifo_fops);
799 if (IS_ERR(res[0])) {
800 err = PTR_ERR(res[0]);
805 res[0]->private_data = inode->i_pipe;
806 res[0]->f_flags = O_RDONLY | (flags & O_NONBLOCK);
813 free_pipe_info(inode->i_pipe);
818 free_pipe_info(inode->i_pipe);
823 static int __do_pipe_flags(int *fd, struct file **files, int flags)
828 if (flags & ~(O_CLOEXEC | O_NONBLOCK | O_DIRECT))
831 error = create_pipe_files(files, flags);
835 error = get_unused_fd_flags(flags);
840 error = get_unused_fd_flags(flags);
845 audit_fd_pair(fdr, fdw);
858 int do_pipe_flags(int *fd, int flags)
860 struct file *files[2];
861 int error = __do_pipe_flags(fd, files, flags);
863 fd_install(fd[0], files[0]);
864 fd_install(fd[1], files[1]);
870 * sys_pipe() is the normal C calling standard for creating
871 * a pipe. It's not the way Unix traditionally does this, though.
873 SYSCALL_DEFINE2(pipe2, int __user *, fildes, int, flags)
875 struct file *files[2];
879 error = __do_pipe_flags(fd, files, flags);
881 if (unlikely(copy_to_user(fildes, fd, sizeof(fd)))) {
884 put_unused_fd(fd[0]);
885 put_unused_fd(fd[1]);
888 fd_install(fd[0], files[0]);
889 fd_install(fd[1], files[1]);
895 SYSCALL_DEFINE1(pipe, int __user *, fildes)
897 return sys_pipe2(fildes, 0);
900 static int wait_for_partner(struct pipe_inode_info *pipe, unsigned int *cnt)
904 while (cur == *cnt) {
906 if (signal_pending(current))
909 return cur == *cnt ? -ERESTARTSYS : 0;
912 static void wake_up_partner(struct pipe_inode_info *pipe)
914 wake_up_interruptible(&pipe->wait);
917 static int fifo_open(struct inode *inode, struct file *filp)
919 struct pipe_inode_info *pipe;
920 bool is_pipe = inode->i_sb->s_magic == PIPEFS_MAGIC;
925 spin_lock(&inode->i_lock);
927 pipe = inode->i_pipe;
929 spin_unlock(&inode->i_lock);
931 spin_unlock(&inode->i_lock);
932 pipe = alloc_pipe_info();
936 spin_lock(&inode->i_lock);
937 if (unlikely(inode->i_pipe)) {
938 inode->i_pipe->files++;
939 spin_unlock(&inode->i_lock);
940 free_pipe_info(pipe);
941 pipe = inode->i_pipe;
943 inode->i_pipe = pipe;
944 spin_unlock(&inode->i_lock);
947 filp->private_data = pipe;
948 /* OK, we have a pipe and it's pinned down */
952 /* We can only do regular read/write on fifos */
953 filp->f_mode &= (FMODE_READ | FMODE_WRITE);
955 switch (filp->f_mode) {
959 * POSIX.1 says that O_NONBLOCK means return with the FIFO
960 * opened, even when there is no process writing the FIFO.
963 if (pipe->readers++ == 0)
964 wake_up_partner(pipe);
966 if (!is_pipe && !pipe->writers) {
967 if ((filp->f_flags & O_NONBLOCK)) {
968 /* suppress POLLHUP until we have
970 filp->f_version = pipe->w_counter;
972 if (wait_for_partner(pipe, &pipe->w_counter))
981 * POSIX.1 says that O_NONBLOCK means return -1 with
982 * errno=ENXIO when there is no process reading the FIFO.
985 if (!is_pipe && (filp->f_flags & O_NONBLOCK) && !pipe->readers)
989 if (!pipe->writers++)
990 wake_up_partner(pipe);
992 if (!is_pipe && !pipe->readers) {
993 if (wait_for_partner(pipe, &pipe->r_counter))
998 case FMODE_READ | FMODE_WRITE:
1001 * POSIX.1 leaves this case "undefined" when O_NONBLOCK is set.
1002 * This implementation will NEVER block on a O_RDWR open, since
1003 * the process can at least talk to itself.
1010 if (pipe->readers == 1 || pipe->writers == 1)
1011 wake_up_partner(pipe);
1020 __pipe_unlock(pipe);
1024 if (!--pipe->readers)
1025 wake_up_interruptible(&pipe->wait);
1030 if (!--pipe->writers)
1031 wake_up_interruptible(&pipe->wait);
1036 __pipe_unlock(pipe);
1038 put_pipe_info(inode, pipe);
1042 const struct file_operations pipefifo_fops = {
1044 .llseek = no_llseek,
1045 .read_iter = pipe_read,
1046 .write_iter = pipe_write,
1048 .unlocked_ioctl = pipe_ioctl,
1049 .release = pipe_release,
1050 .fasync = pipe_fasync,
1054 * Currently we rely on the pipe array holding a power-of-2 number
1055 * of pages. Returns 0 on error.
1057 static inline unsigned int round_pipe_size(unsigned int size)
1059 unsigned long nr_pages;
1061 if (size < pipe_min_size)
1062 size = pipe_min_size;
1064 nr_pages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
1068 return roundup_pow_of_two(nr_pages) << PAGE_SHIFT;
1072 * Allocate a new array of pipe buffers and copy the info over. Returns the
1073 * pipe size if successful, or return -ERROR on error.
1075 static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long arg)
1077 struct pipe_buffer *bufs;
1078 unsigned int size, nr_pages;
1079 unsigned long user_bufs;
1082 size = round_pipe_size(arg);
1085 nr_pages = size >> PAGE_SHIFT;
1091 * If trying to increase the pipe capacity, check that an
1092 * unprivileged user is not trying to exceed various limits
1093 * (soft limit check here, hard limit check just below).
1094 * Decreasing the pipe capacity is always permitted, even
1095 * if the user is currently over a limit.
1097 if (nr_pages > pipe->buffers &&
1098 size > pipe_max_size && !capable(CAP_SYS_RESOURCE))
1101 user_bufs = account_pipe_buffers(pipe->user, pipe->buffers, nr_pages);
1103 if (nr_pages > pipe->buffers &&
1104 (too_many_pipe_buffers_hard(user_bufs) ||
1105 too_many_pipe_buffers_soft(user_bufs)) &&
1106 is_unprivileged_user()) {
1108 goto out_revert_acct;
1112 * We can shrink the pipe, if arg >= pipe->nrbufs. Since we don't
1113 * expect a lot of shrink+grow operations, just free and allocate
1114 * again like we would do for growing. If the pipe currently
1115 * contains more buffers than arg, then return busy.
1117 if (nr_pages < pipe->nrbufs) {
1119 goto out_revert_acct;
1122 bufs = kcalloc(nr_pages, sizeof(*bufs),
1123 GFP_KERNEL_ACCOUNT | __GFP_NOWARN);
1124 if (unlikely(!bufs)) {
1126 goto out_revert_acct;
1130 * The pipe array wraps around, so just start the new one at zero
1131 * and adjust the indexes.
1137 tail = pipe->curbuf + pipe->nrbufs;
1138 if (tail < pipe->buffers)
1141 tail &= (pipe->buffers - 1);
1143 head = pipe->nrbufs - tail;
1145 memcpy(bufs, pipe->bufs + pipe->curbuf, head * sizeof(struct pipe_buffer));
1147 memcpy(bufs + head, pipe->bufs, tail * sizeof(struct pipe_buffer));
1153 pipe->buffers = nr_pages;
1154 return nr_pages * PAGE_SIZE;
1157 (void) account_pipe_buffers(pipe->user, nr_pages, pipe->buffers);
1162 * This should work even if CONFIG_PROC_FS isn't set, as proc_dointvec_minmax
1163 * will return an error.
1165 int pipe_proc_fn(struct ctl_table *table, int write, void __user *buf,
1166 size_t *lenp, loff_t *ppos)
1168 unsigned int rounded_pipe_max_size;
1171 ret = proc_douintvec_minmax(table, write, buf, lenp, ppos);
1172 if (ret < 0 || !write)
1175 rounded_pipe_max_size = round_pipe_size(pipe_max_size);
1176 if (rounded_pipe_max_size == 0)
1179 pipe_max_size = rounded_pipe_max_size;
1184 * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same
1185 * location, so checking ->i_pipe is not enough to verify that this is a
1188 struct pipe_inode_info *get_pipe_info(struct file *file)
1190 return file->f_op == &pipefifo_fops ? file->private_data : NULL;
1193 long pipe_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
1195 struct pipe_inode_info *pipe;
1198 pipe = get_pipe_info(file);
1206 ret = pipe_set_size(pipe, arg);
1209 ret = pipe->buffers * PAGE_SIZE;
1216 __pipe_unlock(pipe);
1220 static const struct super_operations pipefs_ops = {
1221 .destroy_inode = free_inode_nonrcu,
1222 .statfs = simple_statfs,
1226 * pipefs should _never_ be mounted by userland - too much of security hassle,
1227 * no real gain from having the whole whorehouse mounted. So we don't need
1228 * any operations on the root directory. However, we need a non-trivial
1229 * d_name - pipe: will go nicely and kill the special-casing in procfs.
1231 static struct dentry *pipefs_mount(struct file_system_type *fs_type,
1232 int flags, const char *dev_name, void *data)
1234 return mount_pseudo(fs_type, "pipe:", &pipefs_ops,
1235 &pipefs_dentry_operations, PIPEFS_MAGIC);
1238 static struct file_system_type pipe_fs_type = {
1240 .mount = pipefs_mount,
1241 .kill_sb = kill_anon_super,
1244 static int __init init_pipe_fs(void)
1246 int err = register_filesystem(&pipe_fs_type);
1249 pipe_mnt = kern_mount(&pipe_fs_type);
1250 if (IS_ERR(pipe_mnt)) {
1251 err = PTR_ERR(pipe_mnt);
1252 unregister_filesystem(&pipe_fs_type);
1258 fs_initcall(init_pipe_fs);