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-rw-r--r--fs/pipe.c1508
1 files changed, 1508 insertions, 0 deletions
diff --git a/fs/pipe.c b/fs/pipe.c
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+++ b/fs/pipe.c
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+// SPDX-License-Identifier: GPL-2.0
+/*
+ * linux/fs/pipe.c
+ *
+ * Copyright (C) 1991, 1992, 1999 Linus Torvalds
+ */
+
+#include <linux/mm.h>
+#include <linux/file.h>
+#include <linux/poll.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/fs.h>
+#include <linux/log2.h>
+#include <linux/mount.h>
+#include <linux/pseudo_fs.h>
+#include <linux/magic.h>
+#include <linux/pipe_fs_i.h>
+#include <linux/uio.h>
+#include <linux/highmem.h>
+#include <linux/pagemap.h>
+#include <linux/audit.h>
+#include <linux/syscalls.h>
+#include <linux/fcntl.h>
+#include <linux/memcontrol.h>
+#include <linux/watch_queue.h>
+#include <linux/sysctl.h>
+
+#include <linux/uaccess.h>
+#include <asm/ioctls.h>
+
+#include "internal.h"
+
+/*
+ * New pipe buffers will be restricted to this size while the user is exceeding
+ * their pipe buffer quota. The general pipe use case needs at least two
+ * buffers: one for data yet to be read, and one for new data. If this is less
+ * than two, then a write to a non-empty pipe may block even if the pipe is not
+ * full. This can occur with GNU make jobserver or similar uses of pipes as
+ * semaphores: multiple processes may be waiting to write tokens back to the
+ * pipe before reading tokens: https://lore.kernel.org/lkml/1628086770.5rn8p04n6j.none@localhost/.
+ *
+ * Users can reduce their pipe buffers with F_SETPIPE_SZ below this at their
+ * own risk, namely: pipe writes to non-full pipes may block until the pipe is
+ * emptied.
+ */
+#define PIPE_MIN_DEF_BUFFERS 2
+
+/*
+ * The max size that a non-root user is allowed to grow the pipe. Can
+ * be set by root in /proc/sys/fs/pipe-max-size
+ */
+static unsigned int pipe_max_size = 1048576;
+
+/* Maximum allocatable pages per user. Hard limit is unset by default, soft
+ * matches default values.
+ */
+static unsigned long pipe_user_pages_hard;
+static unsigned long pipe_user_pages_soft = PIPE_DEF_BUFFERS * INR_OPEN_CUR;
+
+/*
+ * We use head and tail indices that aren't masked off, except at the point of
+ * dereference, but rather they're allowed to wrap naturally. This means there
+ * isn't a dead spot in the buffer, but the ring has to be a power of two and
+ * <= 2^31.
+ * -- David Howells 2019-09-23.
+ *
+ * Reads with count = 0 should always return 0.
+ * -- Julian Bradfield 1999-06-07.
+ *
+ * FIFOs and Pipes now generate SIGIO for both readers and writers.
+ * -- Jeremy Elson <jelson@circlemud.org> 2001-08-16
+ *
+ * pipe_read & write cleanup
+ * -- Manfred Spraul <manfred@colorfullife.com> 2002-05-09
+ */
+
+static void pipe_lock_nested(struct pipe_inode_info *pipe, int subclass)
+{
+ if (pipe->files)
+ mutex_lock_nested(&pipe->mutex, subclass);
+}
+
+void pipe_lock(struct pipe_inode_info *pipe)
+{
+ /*
+ * pipe_lock() nests non-pipe inode locks (for writing to a file)
+ */
+ pipe_lock_nested(pipe, I_MUTEX_PARENT);
+}
+EXPORT_SYMBOL(pipe_lock);
+
+void pipe_unlock(struct pipe_inode_info *pipe)
+{
+ if (pipe->files)
+ mutex_unlock(&pipe->mutex);
+}
+EXPORT_SYMBOL(pipe_unlock);
+
+static inline void __pipe_lock(struct pipe_inode_info *pipe)
+{
+ mutex_lock_nested(&pipe->mutex, I_MUTEX_PARENT);
+}
+
+static inline void __pipe_unlock(struct pipe_inode_info *pipe)
+{
+ mutex_unlock(&pipe->mutex);
+}
+
+void pipe_double_lock(struct pipe_inode_info *pipe1,
+ struct pipe_inode_info *pipe2)
+{
+ BUG_ON(pipe1 == pipe2);
+
+ if (pipe1 < pipe2) {
+ pipe_lock_nested(pipe1, I_MUTEX_PARENT);
+ pipe_lock_nested(pipe2, I_MUTEX_CHILD);
+ } else {
+ pipe_lock_nested(pipe2, I_MUTEX_PARENT);
+ pipe_lock_nested(pipe1, I_MUTEX_CHILD);
+ }
+}
+
+static void anon_pipe_buf_release(struct pipe_inode_info *pipe,
+ struct pipe_buffer *buf)
+{
+ struct page *page = buf->page;
+
+ /*
+ * If nobody else uses this page, and we don't already have a
+ * temporary page, let's keep track of it as a one-deep
+ * allocation cache. (Otherwise just release our reference to it)
+ */
+ if (page_count(page) == 1 && !pipe->tmp_page)
+ pipe->tmp_page = page;
+ else
+ put_page(page);
+}
+
+static bool anon_pipe_buf_try_steal(struct pipe_inode_info *pipe,
+ struct pipe_buffer *buf)
+{
+ struct page *page = buf->page;
+
+ if (page_count(page) != 1)
+ return false;
+ memcg_kmem_uncharge_page(page, 0);
+ __SetPageLocked(page);
+ return true;
+}
+
+/**
+ * generic_pipe_buf_try_steal - attempt to take ownership of a &pipe_buffer
+ * @pipe: the pipe that the buffer belongs to
+ * @buf: the buffer to attempt to steal
+ *
+ * Description:
+ * This function attempts to steal the &struct page attached to
+ * @buf. If successful, this function returns 0 and returns with
+ * the page locked. The caller may then reuse the page for whatever
+ * he wishes; the typical use is insertion into a different file
+ * page cache.
+ */
+bool generic_pipe_buf_try_steal(struct pipe_inode_info *pipe,
+ struct pipe_buffer *buf)
+{
+ struct page *page = buf->page;
+
+ /*
+ * A reference of one is golden, that means that the owner of this
+ * page is the only one holding a reference to it. lock the page
+ * and return OK.
+ */
+ if (page_count(page) == 1) {
+ lock_page(page);
+ return true;
+ }
+ return false;
+}
+EXPORT_SYMBOL(generic_pipe_buf_try_steal);
+
+/**
+ * generic_pipe_buf_get - get a reference to a &struct pipe_buffer
+ * @pipe: the pipe that the buffer belongs to
+ * @buf: the buffer to get a reference to
+ *
+ * Description:
+ * This function grabs an extra reference to @buf. It's used in
+ * the tee() system call, when we duplicate the buffers in one
+ * pipe into another.
+ */
+bool generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
+{
+ return try_get_page(buf->page);
+}
+EXPORT_SYMBOL(generic_pipe_buf_get);
+
+/**
+ * generic_pipe_buf_release - put a reference to a &struct pipe_buffer
+ * @pipe: the pipe that the buffer belongs to
+ * @buf: the buffer to put a reference to
+ *
+ * Description:
+ * This function releases a reference to @buf.
+ */
+void generic_pipe_buf_release(struct pipe_inode_info *pipe,
+ struct pipe_buffer *buf)
+{
+ put_page(buf->page);
+}
+EXPORT_SYMBOL(generic_pipe_buf_release);
+
+static const struct pipe_buf_operations anon_pipe_buf_ops = {
+ .release = anon_pipe_buf_release,
+ .try_steal = anon_pipe_buf_try_steal,
+ .get = generic_pipe_buf_get,
+};
+
+/* Done while waiting without holding the pipe lock - thus the READ_ONCE() */
+static inline bool pipe_readable(const struct pipe_inode_info *pipe)
+{
+ unsigned int head = READ_ONCE(pipe->head);
+ unsigned int tail = READ_ONCE(pipe->tail);
+ unsigned int writers = READ_ONCE(pipe->writers);
+
+ return !pipe_empty(head, tail) || !writers;
+}
+
+static ssize_t
+pipe_read(struct kiocb *iocb, struct iov_iter *to)
+{
+ size_t total_len = iov_iter_count(to);
+ struct file *filp = iocb->ki_filp;
+ struct pipe_inode_info *pipe = filp->private_data;
+ bool was_full, wake_next_reader = false;
+ ssize_t ret;
+
+ /* Null read succeeds. */
+ if (unlikely(total_len == 0))
+ return 0;
+
+ ret = 0;
+ __pipe_lock(pipe);
+
+ /*
+ * We only wake up writers if the pipe was full when we started
+ * reading in order to avoid unnecessary wakeups.
+ *
+ * But when we do wake up writers, we do so using a sync wakeup
+ * (WF_SYNC), because we want them to get going and generate more
+ * data for us.
+ */
+ was_full = pipe_full(pipe->head, pipe->tail, pipe->max_usage);
+ for (;;) {
+ /* Read ->head with a barrier vs post_one_notification() */
+ unsigned int head = smp_load_acquire(&pipe->head);
+ unsigned int tail = pipe->tail;
+ unsigned int mask = pipe->ring_size - 1;
+
+#ifdef CONFIG_WATCH_QUEUE
+ if (pipe->note_loss) {
+ struct watch_notification n;
+
+ if (total_len < 8) {
+ if (ret == 0)
+ ret = -ENOBUFS;
+ break;
+ }
+
+ n.type = WATCH_TYPE_META;
+ n.subtype = WATCH_META_LOSS_NOTIFICATION;
+ n.info = watch_sizeof(n);
+ if (copy_to_iter(&n, sizeof(n), to) != sizeof(n)) {
+ if (ret == 0)
+ ret = -EFAULT;
+ break;
+ }
+ ret += sizeof(n);
+ total_len -= sizeof(n);
+ pipe->note_loss = false;
+ }
+#endif
+
+ if (!pipe_empty(head, tail)) {
+ struct pipe_buffer *buf = &pipe->bufs[tail & mask];
+ size_t chars = buf->len;
+ size_t written;
+ int error;
+
+ if (chars > total_len) {
+ if (buf->flags & PIPE_BUF_FLAG_WHOLE) {
+ if (ret == 0)
+ ret = -ENOBUFS;
+ break;
+ }
+ chars = total_len;
+ }
+
+ error = pipe_buf_confirm(pipe, buf);
+ if (error) {
+ if (!ret)
+ ret = error;
+ break;
+ }
+
+ written = copy_page_to_iter(buf->page, buf->offset, chars, to);
+ if (unlikely(written < chars)) {
+ if (!ret)
+ ret = -EFAULT;
+ break;
+ }
+ ret += chars;
+ buf->offset += chars;
+ buf->len -= chars;
+
+ /* Was it a packet buffer? Clean up and exit */
+ if (buf->flags & PIPE_BUF_FLAG_PACKET) {
+ total_len = chars;
+ buf->len = 0;
+ }
+
+ if (!buf->len) {
+ pipe_buf_release(pipe, buf);
+ spin_lock_irq(&pipe->rd_wait.lock);
+#ifdef CONFIG_WATCH_QUEUE
+ if (buf->flags & PIPE_BUF_FLAG_LOSS)
+ pipe->note_loss = true;
+#endif
+ tail++;
+ pipe->tail = tail;
+ spin_unlock_irq(&pipe->rd_wait.lock);
+ }
+ total_len -= chars;
+ if (!total_len)
+ break; /* common path: read succeeded */
+ if (!pipe_empty(head, tail)) /* More to do? */
+ continue;
+ }
+
+ if (!pipe->writers)
+ break;
+ if (ret)
+ break;
+ if (filp->f_flags & O_NONBLOCK) {
+ ret = -EAGAIN;
+ break;
+ }
+ __pipe_unlock(pipe);
+
+ /*
+ * We only get here if we didn't actually read anything.
+ *
+ * However, we could have seen (and removed) a zero-sized
+ * pipe buffer, and might have made space in the buffers
+ * that way.
+ *
+ * You can't make zero-sized pipe buffers by doing an empty
+ * write (not even in packet mode), but they can happen if
+ * the writer gets an EFAULT when trying to fill a buffer
+ * that already got allocated and inserted in the buffer
+ * array.
+ *
+ * So we still need to wake up any pending writers in the
+ * _very_ unlikely case that the pipe was full, but we got
+ * no data.
+ */
+ if (unlikely(was_full))
+ wake_up_interruptible_sync_poll(&pipe->wr_wait, EPOLLOUT | EPOLLWRNORM);
+ kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
+
+ /*
+ * But because we didn't read anything, at this point we can
+ * just return directly with -ERESTARTSYS if we're interrupted,
+ * since we've done any required wakeups and there's no need
+ * to mark anything accessed. And we've dropped the lock.
+ */
+ if (wait_event_interruptible_exclusive(pipe->rd_wait, pipe_readable(pipe)) < 0)
+ return -ERESTARTSYS;
+
+ __pipe_lock(pipe);
+ was_full = pipe_full(pipe->head, pipe->tail, pipe->max_usage);
+ wake_next_reader = true;
+ }
+ if (pipe_empty(pipe->head, pipe->tail))
+ wake_next_reader = false;
+ __pipe_unlock(pipe);
+
+ if (was_full)
+ wake_up_interruptible_sync_poll(&pipe->wr_wait, EPOLLOUT | EPOLLWRNORM);
+ if (wake_next_reader)
+ wake_up_interruptible_sync_poll(&pipe->rd_wait, EPOLLIN | EPOLLRDNORM);
+ kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
+ if (ret > 0)
+ file_accessed(filp);
+ return ret;
+}
+
+static inline int is_packetized(struct file *file)
+{
+ return (file->f_flags & O_DIRECT) != 0;
+}
+
+/* Done while waiting without holding the pipe lock - thus the READ_ONCE() */
+static inline bool pipe_writable(const struct pipe_inode_info *pipe)
+{
+ unsigned int head = READ_ONCE(pipe->head);
+ unsigned int tail = READ_ONCE(pipe->tail);
+ unsigned int max_usage = READ_ONCE(pipe->max_usage);
+
+ return !pipe_full(head, tail, max_usage) ||
+ !READ_ONCE(pipe->readers);
+}
+
+static ssize_t
+pipe_write(struct kiocb *iocb, struct iov_iter *from)
+{
+ struct file *filp = iocb->ki_filp;
+ struct pipe_inode_info *pipe = filp->private_data;
+ unsigned int head;
+ ssize_t ret = 0;
+ size_t total_len = iov_iter_count(from);
+ ssize_t chars;
+ bool was_empty = false;
+ bool wake_next_writer = false;
+
+ /* Null write succeeds. */
+ if (unlikely(total_len == 0))
+ return 0;
+
+ __pipe_lock(pipe);
+
+ if (!pipe->readers) {
+ send_sig(SIGPIPE, current, 0);
+ ret = -EPIPE;
+ goto out;
+ }
+
+ if (pipe_has_watch_queue(pipe)) {
+ ret = -EXDEV;
+ goto out;
+ }
+
+ /*
+ * If it wasn't empty we try to merge new data into
+ * the last buffer.
+ *
+ * That naturally merges small writes, but it also
+ * page-aligns the rest of the writes for large writes
+ * spanning multiple pages.
+ */
+ head = pipe->head;
+ was_empty = pipe_empty(head, pipe->tail);
+ chars = total_len & (PAGE_SIZE-1);
+ if (chars && !was_empty) {
+ unsigned int mask = pipe->ring_size - 1;
+ struct pipe_buffer *buf = &pipe->bufs[(head - 1) & mask];
+ int offset = buf->offset + buf->len;
+
+ if ((buf->flags & PIPE_BUF_FLAG_CAN_MERGE) &&
+ offset + chars <= PAGE_SIZE) {
+ ret = pipe_buf_confirm(pipe, buf);
+ if (ret)
+ goto out;
+
+ ret = copy_page_from_iter(buf->page, offset, chars, from);
+ if (unlikely(ret < chars)) {
+ ret = -EFAULT;
+ goto out;
+ }
+
+ buf->len += ret;
+ if (!iov_iter_count(from))
+ goto out;
+ }
+ }
+
+ for (;;) {
+ if (!pipe->readers) {
+ send_sig(SIGPIPE, current, 0);
+ if (!ret)
+ ret = -EPIPE;
+ break;
+ }
+
+ head = pipe->head;
+ if (!pipe_full(head, pipe->tail, pipe->max_usage)) {
+ unsigned int mask = pipe->ring_size - 1;
+ struct pipe_buffer *buf = &pipe->bufs[head & mask];
+ struct page *page = pipe->tmp_page;
+ int copied;
+
+ if (!page) {
+ page = alloc_page(GFP_HIGHUSER | __GFP_ACCOUNT);
+ if (unlikely(!page)) {
+ ret = ret ? : -ENOMEM;
+ break;
+ }
+ pipe->tmp_page = page;
+ }
+
+ /* Allocate a slot in the ring in advance and attach an
+ * empty buffer. If we fault or otherwise fail to use
+ * it, either the reader will consume it or it'll still
+ * be there for the next write.
+ */
+ spin_lock_irq(&pipe->rd_wait.lock);
+
+ head = pipe->head;
+ if (pipe_full(head, pipe->tail, pipe->max_usage)) {
+ spin_unlock_irq(&pipe->rd_wait.lock);
+ continue;
+ }
+
+ pipe->head = head + 1;
+ spin_unlock_irq(&pipe->rd_wait.lock);
+
+ /* Insert it into the buffer array */
+ buf = &pipe->bufs[head & mask];
+ buf->page = page;
+ buf->ops = &anon_pipe_buf_ops;
+ buf->offset = 0;
+ buf->len = 0;
+ if (is_packetized(filp))
+ buf->flags = PIPE_BUF_FLAG_PACKET;
+ else
+ buf->flags = PIPE_BUF_FLAG_CAN_MERGE;
+ pipe->tmp_page = NULL;
+
+ copied = copy_page_from_iter(page, 0, PAGE_SIZE, from);
+ if (unlikely(copied < PAGE_SIZE && iov_iter_count(from))) {
+ if (!ret)
+ ret = -EFAULT;
+ break;
+ }
+ ret += copied;
+ buf->offset = 0;
+ buf->len = copied;
+
+ if (!iov_iter_count(from))
+ break;
+ }
+
+ if (!pipe_full(head, pipe->tail, pipe->max_usage))
+ continue;
+
+ /* Wait for buffer space to become available. */
+ if (filp->f_flags & O_NONBLOCK) {
+ if (!ret)
+ ret = -EAGAIN;
+ break;
+ }
+ if (signal_pending(current)) {
+ if (!ret)
+ ret = -ERESTARTSYS;
+ break;
+ }
+
+ /*
+ * We're going to release the pipe lock and wait for more
+ * space. We wake up any readers if necessary, and then
+ * after waiting we need to re-check whether the pipe
+ * become empty while we dropped the lock.
+ */
+ __pipe_unlock(pipe);
+ if (was_empty)
+ wake_up_interruptible_sync_poll(&pipe->rd_wait, EPOLLIN | EPOLLRDNORM);
+ kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
+ wait_event_interruptible_exclusive(pipe->wr_wait, pipe_writable(pipe));
+ __pipe_lock(pipe);
+ was_empty = pipe_empty(pipe->head, pipe->tail);
+ wake_next_writer = true;
+ }
+out:
+ if (pipe_full(pipe->head, pipe->tail, pipe->max_usage))
+ wake_next_writer = false;
+ __pipe_unlock(pipe);
+
+ /*
+ * If we do do a wakeup event, we do a 'sync' wakeup, because we
+ * want the reader to start processing things asap, rather than
+ * leave the data pending.
+ *
+ * This is particularly important for small writes, because of
+ * how (for example) the GNU make jobserver uses small writes to
+ * wake up pending jobs
+ *
+ * Epoll nonsensically wants a wakeup whether the pipe
+ * was already empty or not.
+ */
+ if (was_empty || pipe->poll_usage)
+ wake_up_interruptible_sync_poll(&pipe->rd_wait, EPOLLIN | EPOLLRDNORM);
+ kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
+ if (wake_next_writer)
+ wake_up_interruptible_sync_poll(&pipe->wr_wait, EPOLLOUT | EPOLLWRNORM);
+ if (ret > 0 && sb_start_write_trylock(file_inode(filp)->i_sb)) {
+ int err = file_update_time(filp);
+ if (err)
+ ret = err;
+ sb_end_write(file_inode(filp)->i_sb);
+ }
+ return ret;
+}
+
+static long pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
+{
+ struct pipe_inode_info *pipe = filp->private_data;
+ unsigned int count, head, tail, mask;
+
+ switch (cmd) {
+ case FIONREAD:
+ __pipe_lock(pipe);
+ count = 0;
+ head = pipe->head;
+ tail = pipe->tail;
+ mask = pipe->ring_size - 1;
+
+ while (tail != head) {
+ count += pipe->bufs[tail & mask].len;
+ tail++;
+ }
+ __pipe_unlock(pipe);
+
+ return put_user(count, (int __user *)arg);
+
+#ifdef CONFIG_WATCH_QUEUE
+ case IOC_WATCH_QUEUE_SET_SIZE: {
+ int ret;
+ __pipe_lock(pipe);
+ ret = watch_queue_set_size(pipe, arg);
+ __pipe_unlock(pipe);
+ return ret;
+ }
+
+ case IOC_WATCH_QUEUE_SET_FILTER:
+ return watch_queue_set_filter(
+ pipe, (struct watch_notification_filter __user *)arg);
+#endif
+
+ default:
+ return -ENOIOCTLCMD;
+ }
+}
+
+/* No kernel lock held - fine */
+static __poll_t
+pipe_poll(struct file *filp, poll_table *wait)
+{
+ __poll_t mask;
+ struct pipe_inode_info *pipe = filp->private_data;
+ unsigned int head, tail;
+
+ /* Epoll has some historical nasty semantics, this enables them */
+ WRITE_ONCE(pipe->poll_usage, true);
+
+ /*
+ * Reading pipe state only -- no need for acquiring the semaphore.
+ *
+ * But because this is racy, the code has to add the
+ * entry to the poll table _first_ ..
+ */
+ if (filp->f_mode & FMODE_READ)
+ poll_wait(filp, &pipe->rd_wait, wait);
+ if (filp->f_mode & FMODE_WRITE)
+ poll_wait(filp, &pipe->wr_wait, wait);
+
+ /*
+ * .. and only then can you do the racy tests. That way,
+ * if something changes and you got it wrong, the poll
+ * table entry will wake you up and fix it.
+ */
+ head = READ_ONCE(pipe->head);
+ tail = READ_ONCE(pipe->tail);
+
+ mask = 0;
+ if (filp->f_mode & FMODE_READ) {
+ if (!pipe_empty(head, tail))
+ mask |= EPOLLIN | EPOLLRDNORM;
+ if (!pipe->writers && filp->f_version != pipe->w_counter)
+ mask |= EPOLLHUP;
+ }
+
+ if (filp->f_mode & FMODE_WRITE) {
+ if (!pipe_full(head, tail, pipe->max_usage))
+ mask |= EPOLLOUT | EPOLLWRNORM;
+ /*
+ * Most Unices do not set EPOLLERR for FIFOs but on Linux they
+ * behave exactly like pipes for poll().
+ */
+ if (!pipe->readers)
+ mask |= EPOLLERR;
+ }
+
+ return mask;
+}
+
+static void put_pipe_info(struct inode *inode, struct pipe_inode_info *pipe)
+{
+ int kill = 0;
+
+ spin_lock(&inode->i_lock);
+ if (!--pipe->files) {
+ inode->i_pipe = NULL;
+ kill = 1;
+ }
+ spin_unlock(&inode->i_lock);
+
+ if (kill)
+ free_pipe_info(pipe);
+}
+
+static int
+pipe_release(struct inode *inode, struct file *file)
+{
+ struct pipe_inode_info *pipe = file->private_data;
+
+ __pipe_lock(pipe);
+ if (file->f_mode & FMODE_READ)
+ pipe->readers--;
+ if (file->f_mode & FMODE_WRITE)
+ pipe->writers--;
+
+ /* Was that the last reader or writer, but not the other side? */
+ if (!pipe->readers != !pipe->writers) {
+ wake_up_interruptible_all(&pipe->rd_wait);
+ wake_up_interruptible_all(&pipe->wr_wait);
+ kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
+ kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
+ }
+ __pipe_unlock(pipe);
+
+ put_pipe_info(inode, pipe);
+ return 0;
+}
+
+static int
+pipe_fasync(int fd, struct file *filp, int on)
+{
+ struct pipe_inode_info *pipe = filp->private_data;
+ int retval = 0;
+
+ __pipe_lock(pipe);
+ if (filp->f_mode & FMODE_READ)
+ retval = fasync_helper(fd, filp, on, &pipe->fasync_readers);
+ if ((filp->f_mode & FMODE_WRITE) && retval >= 0) {
+ retval = fasync_helper(fd, filp, on, &pipe->fasync_writers);
+ if (retval < 0 && (filp->f_mode & FMODE_READ))
+ /* this can happen only if on == T */
+ fasync_helper(-1, filp, 0, &pipe->fasync_readers);
+ }
+ __pipe_unlock(pipe);
+ return retval;
+}
+
+unsigned long account_pipe_buffers(struct user_struct *user,
+ unsigned long old, unsigned long new)
+{
+ return atomic_long_add_return(new - old, &user->pipe_bufs);
+}
+
+bool too_many_pipe_buffers_soft(unsigned long user_bufs)
+{
+ unsigned long soft_limit = READ_ONCE(pipe_user_pages_soft);
+
+ return soft_limit && user_bufs > soft_limit;
+}
+
+bool too_many_pipe_buffers_hard(unsigned long user_bufs)
+{
+ unsigned long hard_limit = READ_ONCE(pipe_user_pages_hard);
+
+ return hard_limit && user_bufs > hard_limit;
+}
+
+bool pipe_is_unprivileged_user(void)
+{
+ return !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN);
+}
+
+struct pipe_inode_info *alloc_pipe_info(void)
+{
+ struct pipe_inode_info *pipe;
+ unsigned long pipe_bufs = PIPE_DEF_BUFFERS;
+ struct user_struct *user = get_current_user();
+ unsigned long user_bufs;
+ unsigned int max_size = READ_ONCE(pipe_max_size);
+
+ pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL_ACCOUNT);
+ if (pipe == NULL)
+ goto out_free_uid;
+
+ if (pipe_bufs * PAGE_SIZE > max_size && !capable(CAP_SYS_RESOURCE))
+ pipe_bufs = max_size >> PAGE_SHIFT;
+
+ user_bufs = account_pipe_buffers(user, 0, pipe_bufs);
+
+ if (too_many_pipe_buffers_soft(user_bufs) && pipe_is_unprivileged_user()) {
+ user_bufs = account_pipe_buffers(user, pipe_bufs, PIPE_MIN_DEF_BUFFERS);
+ pipe_bufs = PIPE_MIN_DEF_BUFFERS;
+ }
+
+ if (too_many_pipe_buffers_hard(user_bufs) && pipe_is_unprivileged_user())
+ goto out_revert_acct;
+
+ pipe->bufs = kcalloc(pipe_bufs, sizeof(struct pipe_buffer),
+ GFP_KERNEL_ACCOUNT);
+
+ if (pipe->bufs) {
+ init_waitqueue_head(&pipe->rd_wait);
+ init_waitqueue_head(&pipe->wr_wait);
+ pipe->r_counter = pipe->w_counter = 1;
+ pipe->max_usage = pipe_bufs;
+ pipe->ring_size = pipe_bufs;
+ pipe->nr_accounted = pipe_bufs;
+ pipe->user = user;
+ mutex_init(&pipe->mutex);
+ return pipe;
+ }
+
+out_revert_acct:
+ (void) account_pipe_buffers(user, pipe_bufs, 0);
+ kfree(pipe);
+out_free_uid:
+ free_uid(user);
+ return NULL;
+}
+
+void free_pipe_info(struct pipe_inode_info *pipe)
+{
+ unsigned int i;
+
+#ifdef CONFIG_WATCH_QUEUE
+ if (pipe->watch_queue)
+ watch_queue_clear(pipe->watch_queue);
+#endif
+
+ (void) account_pipe_buffers(pipe->user, pipe->nr_accounted, 0);
+ free_uid(pipe->user);
+ for (i = 0; i < pipe->ring_size; i++) {
+ struct pipe_buffer *buf = pipe->bufs + i;
+ if (buf->ops)
+ pipe_buf_release(pipe, buf);
+ }
+#ifdef CONFIG_WATCH_QUEUE
+ if (pipe->watch_queue)
+ put_watch_queue(pipe->watch_queue);
+#endif
+ if (pipe->tmp_page)
+ __free_page(pipe->tmp_page);
+ kfree(pipe->bufs);
+ kfree(pipe);
+}
+
+static struct vfsmount *pipe_mnt __read_mostly;
+
+/*
+ * pipefs_dname() is called from d_path().
+ */
+static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen)
+{
+ return dynamic_dname(buffer, buflen, "pipe:[%lu]",
+ d_inode(dentry)->i_ino);
+}
+
+static const struct dentry_operations pipefs_dentry_operations = {
+ .d_dname = pipefs_dname,
+};
+
+static struct inode * get_pipe_inode(void)
+{
+ struct inode *inode = new_inode_pseudo(pipe_mnt->mnt_sb);
+ struct pipe_inode_info *pipe;
+
+ if (!inode)
+ goto fail_inode;
+
+ inode->i_ino = get_next_ino();
+
+ pipe = alloc_pipe_info();
+ if (!pipe)
+ goto fail_iput;
+
+ inode->i_pipe = pipe;
+ pipe->files = 2;
+ pipe->readers = pipe->writers = 1;
+ inode->i_fop = &pipefifo_fops;
+
+ /*
+ * Mark the inode dirty from the very beginning,
+ * that way it will never be moved to the dirty
+ * list because "mark_inode_dirty()" will think
+ * that it already _is_ on the dirty list.
+ */
+ inode->i_state = I_DIRTY;
+ inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR;
+ inode->i_uid = current_fsuid();
+ inode->i_gid = current_fsgid();
+ inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
+
+ return inode;
+
+fail_iput:
+ iput(inode);
+
+fail_inode:
+ return NULL;
+}
+
+int create_pipe_files(struct file **res, int flags)
+{
+ struct inode *inode = get_pipe_inode();
+ struct file *f;
+ int error;
+
+ if (!inode)
+ return -ENFILE;
+
+ if (flags & O_NOTIFICATION_PIPE) {
+ error = watch_queue_init(inode->i_pipe);
+ if (error) {
+ free_pipe_info(inode->i_pipe);
+ iput(inode);
+ return error;
+ }
+ }
+
+ f = alloc_file_pseudo(inode, pipe_mnt, "",
+ O_WRONLY | (flags & (O_NONBLOCK | O_DIRECT)),
+ &pipefifo_fops);
+ if (IS_ERR(f)) {
+ free_pipe_info(inode->i_pipe);
+ iput(inode);
+ return PTR_ERR(f);
+ }
+
+ f->private_data = inode->i_pipe;
+
+ res[0] = alloc_file_clone(f, O_RDONLY | (flags & O_NONBLOCK),
+ &pipefifo_fops);
+ if (IS_ERR(res[0])) {
+ put_pipe_info(inode, inode->i_pipe);
+ fput(f);
+ return PTR_ERR(res[0]);
+ }
+ res[0]->private_data = inode->i_pipe;
+ res[1] = f;
+ stream_open(inode, res[0]);
+ stream_open(inode, res[1]);
+ return 0;
+}
+
+static int __do_pipe_flags(int *fd, struct file **files, int flags)
+{
+ int error;
+ int fdw, fdr;
+
+ if (flags & ~(O_CLOEXEC | O_NONBLOCK | O_DIRECT | O_NOTIFICATION_PIPE))
+ return -EINVAL;
+
+ error = create_pipe_files(files, flags);
+ if (error)
+ return error;
+
+ error = get_unused_fd_flags(flags);
+ if (error < 0)
+ goto err_read_pipe;
+ fdr = error;
+
+ error = get_unused_fd_flags(flags);
+ if (error < 0)
+ goto err_fdr;
+ fdw = error;
+
+ audit_fd_pair(fdr, fdw);
+ fd[0] = fdr;
+ fd[1] = fdw;
+ return 0;
+
+ err_fdr:
+ put_unused_fd(fdr);
+ err_read_pipe:
+ fput(files[0]);
+ fput(files[1]);
+ return error;
+}
+
+int do_pipe_flags(int *fd, int flags)
+{
+ struct file *files[2];
+ int error = __do_pipe_flags(fd, files, flags);
+ if (!error) {
+ fd_install(fd[0], files[0]);
+ fd_install(fd[1], files[1]);
+ }
+ return error;
+}
+
+/*
+ * sys_pipe() is the normal C calling standard for creating
+ * a pipe. It's not the way Unix traditionally does this, though.
+ */
+static int do_pipe2(int __user *fildes, int flags)
+{
+ struct file *files[2];
+ int fd[2];
+ int error;
+
+ error = __do_pipe_flags(fd, files, flags);
+ if (!error) {
+ if (unlikely(copy_to_user(fildes, fd, sizeof(fd)))) {
+ fput(files[0]);
+ fput(files[1]);
+ put_unused_fd(fd[0]);
+ put_unused_fd(fd[1]);
+ error = -EFAULT;
+ } else {
+ fd_install(fd[0], files[0]);
+ fd_install(fd[1], files[1]);
+ }
+ }
+ return error;
+}
+
+SYSCALL_DEFINE2(pipe2, int __user *, fildes, int, flags)
+{
+ return do_pipe2(fildes, flags);
+}
+
+SYSCALL_DEFINE1(pipe, int __user *, fildes)
+{
+ return do_pipe2(fildes, 0);
+}
+
+/*
+ * This is the stupid "wait for pipe to be readable or writable"
+ * model.
+ *
+ * See pipe_read/write() for the proper kind of exclusive wait,
+ * but that requires that we wake up any other readers/writers
+ * if we then do not end up reading everything (ie the whole
+ * "wake_next_reader/writer" logic in pipe_read/write()).
+ */
+void pipe_wait_readable(struct pipe_inode_info *pipe)
+{
+ pipe_unlock(pipe);
+ wait_event_interruptible(pipe->rd_wait, pipe_readable(pipe));
+ pipe_lock(pipe);
+}
+
+void pipe_wait_writable(struct pipe_inode_info *pipe)
+{
+ pipe_unlock(pipe);
+ wait_event_interruptible(pipe->wr_wait, pipe_writable(pipe));
+ pipe_lock(pipe);
+}
+
+/*
+ * This depends on both the wait (here) and the wakeup (wake_up_partner)
+ * holding the pipe lock, so "*cnt" is stable and we know a wakeup cannot
+ * race with the count check and waitqueue prep.
+ *
+ * Normally in order to avoid races, you'd do the prepare_to_wait() first,
+ * then check the condition you're waiting for, and only then sleep. But
+ * because of the pipe lock, we can check the condition before being on
+ * the wait queue.
+ *
+ * We use the 'rd_wait' waitqueue for pipe partner waiting.
+ */
+static int wait_for_partner(struct pipe_inode_info *pipe, unsigned int *cnt)
+{
+ DEFINE_WAIT(rdwait);
+ int cur = *cnt;
+
+ while (cur == *cnt) {
+ prepare_to_wait(&pipe->rd_wait, &rdwait, TASK_INTERRUPTIBLE);
+ pipe_unlock(pipe);
+ schedule();
+ finish_wait(&pipe->rd_wait, &rdwait);
+ pipe_lock(pipe);
+ if (signal_pending(current))
+ break;
+ }
+ return cur == *cnt ? -ERESTARTSYS : 0;
+}
+
+static void wake_up_partner(struct pipe_inode_info *pipe)
+{
+ wake_up_interruptible_all(&pipe->rd_wait);
+}
+
+static int fifo_open(struct inode *inode, struct file *filp)
+{
+ struct pipe_inode_info *pipe;
+ bool is_pipe = inode->i_sb->s_magic == PIPEFS_MAGIC;
+ int ret;
+
+ filp->f_version = 0;
+
+ spin_lock(&inode->i_lock);
+ if (inode->i_pipe) {
+ pipe = inode->i_pipe;
+ pipe->files++;
+ spin_unlock(&inode->i_lock);
+ } else {
+ spin_unlock(&inode->i_lock);
+ pipe = alloc_pipe_info();
+ if (!pipe)
+ return -ENOMEM;
+ pipe->files = 1;
+ spin_lock(&inode->i_lock);
+ if (unlikely(inode->i_pipe)) {
+ inode->i_pipe->files++;
+ spin_unlock(&inode->i_lock);
+ free_pipe_info(pipe);
+ pipe = inode->i_pipe;
+ } else {
+ inode->i_pipe = pipe;
+ spin_unlock(&inode->i_lock);
+ }
+ }
+ filp->private_data = pipe;
+ /* OK, we have a pipe and it's pinned down */
+
+ __pipe_lock(pipe);
+
+ /* We can only do regular read/write on fifos */
+ stream_open(inode, filp);
+
+ switch (filp->f_mode & (FMODE_READ | FMODE_WRITE)) {
+ case FMODE_READ:
+ /*
+ * O_RDONLY
+ * POSIX.1 says that O_NONBLOCK means return with the FIFO
+ * opened, even when there is no process writing the FIFO.
+ */
+ pipe->r_counter++;
+ if (pipe->readers++ == 0)
+ wake_up_partner(pipe);
+
+ if (!is_pipe && !pipe->writers) {
+ if ((filp->f_flags & O_NONBLOCK)) {
+ /* suppress EPOLLHUP until we have
+ * seen a writer */
+ filp->f_version = pipe->w_counter;
+ } else {
+ if (wait_for_partner(pipe, &pipe->w_counter))
+ goto err_rd;
+ }
+ }
+ break;
+
+ case FMODE_WRITE:
+ /*
+ * O_WRONLY
+ * POSIX.1 says that O_NONBLOCK means return -1 with
+ * errno=ENXIO when there is no process reading the FIFO.
+ */
+ ret = -ENXIO;
+ if (!is_pipe && (filp->f_flags & O_NONBLOCK) && !pipe->readers)
+ goto err;
+
+ pipe->w_counter++;
+ if (!pipe->writers++)
+ wake_up_partner(pipe);
+
+ if (!is_pipe && !pipe->readers) {
+ if (wait_for_partner(pipe, &pipe->r_counter))
+ goto err_wr;
+ }
+ break;
+
+ case FMODE_READ | FMODE_WRITE:
+ /*
+ * O_RDWR
+ * POSIX.1 leaves this case "undefined" when O_NONBLOCK is set.
+ * This implementation will NEVER block on a O_RDWR open, since
+ * the process can at least talk to itself.
+ */
+
+ pipe->readers++;
+ pipe->writers++;
+ pipe->r_counter++;
+ pipe->w_counter++;
+ if (pipe->readers == 1 || pipe->writers == 1)
+ wake_up_partner(pipe);
+ break;
+
+ default:
+ ret = -EINVAL;
+ goto err;
+ }
+
+ /* Ok! */
+ __pipe_unlock(pipe);
+ return 0;
+
+err_rd:
+ if (!--pipe->readers)
+ wake_up_interruptible(&pipe->wr_wait);
+ ret = -ERESTARTSYS;
+ goto err;
+
+err_wr:
+ if (!--pipe->writers)
+ wake_up_interruptible_all(&pipe->rd_wait);
+ ret = -ERESTARTSYS;
+ goto err;
+
+err:
+ __pipe_unlock(pipe);
+
+ put_pipe_info(inode, pipe);
+ return ret;
+}
+
+const struct file_operations pipefifo_fops = {
+ .open = fifo_open,
+ .llseek = no_llseek,
+ .read_iter = pipe_read,
+ .write_iter = pipe_write,
+ .poll = pipe_poll,
+ .unlocked_ioctl = pipe_ioctl,
+ .release = pipe_release,
+ .fasync = pipe_fasync,
+ .splice_write = iter_file_splice_write,
+};
+
+/*
+ * Currently we rely on the pipe array holding a power-of-2 number
+ * of pages. Returns 0 on error.
+ */
+unsigned int round_pipe_size(unsigned long size)
+{
+ if (size > (1U << 31))
+ return 0;
+
+ /* Minimum pipe size, as required by POSIX */
+ if (size < PAGE_SIZE)
+ return PAGE_SIZE;
+
+ return roundup_pow_of_two(size);
+}
+
+/*
+ * Resize the pipe ring to a number of slots.
+ *
+ * Note the pipe can be reduced in capacity, but only if the current
+ * occupancy doesn't exceed nr_slots; if it does, EBUSY will be
+ * returned instead.
+ */
+int pipe_resize_ring(struct pipe_inode_info *pipe, unsigned int nr_slots)
+{
+ struct pipe_buffer *bufs;
+ unsigned int head, tail, mask, n;
+
+ bufs = kcalloc(nr_slots, sizeof(*bufs),
+ GFP_KERNEL_ACCOUNT | __GFP_NOWARN);
+ if (unlikely(!bufs))
+ return -ENOMEM;
+
+ spin_lock_irq(&pipe->rd_wait.lock);
+ mask = pipe->ring_size - 1;
+ head = pipe->head;
+ tail = pipe->tail;
+
+ n = pipe_occupancy(head, tail);
+ if (nr_slots < n) {
+ spin_unlock_irq(&pipe->rd_wait.lock);
+ kfree(bufs);
+ return -EBUSY;
+ }
+
+ /*
+ * The pipe array wraps around, so just start the new one at zero
+ * and adjust the indices.
+ */
+ if (n > 0) {
+ unsigned int h = head & mask;
+ unsigned int t = tail & mask;
+ if (h > t) {
+ memcpy(bufs, pipe->bufs + t,
+ n * sizeof(struct pipe_buffer));
+ } else {
+ unsigned int tsize = pipe->ring_size - t;
+ if (h > 0)
+ memcpy(bufs + tsize, pipe->bufs,
+ h * sizeof(struct pipe_buffer));
+ memcpy(bufs, pipe->bufs + t,
+ tsize * sizeof(struct pipe_buffer));
+ }
+ }
+
+ head = n;
+ tail = 0;
+
+ kfree(pipe->bufs);
+ pipe->bufs = bufs;
+ pipe->ring_size = nr_slots;
+ if (pipe->max_usage > nr_slots)
+ pipe->max_usage = nr_slots;
+ pipe->tail = tail;
+ pipe->head = head;
+
+ if (!pipe_has_watch_queue(pipe)) {
+ pipe->max_usage = nr_slots;
+ pipe->nr_accounted = nr_slots;
+ }
+
+ spin_unlock_irq(&pipe->rd_wait.lock);
+
+ /* This might have made more room for writers */
+ wake_up_interruptible(&pipe->wr_wait);
+ return 0;
+}
+
+/*
+ * Allocate a new array of pipe buffers and copy the info over. Returns the
+ * pipe size if successful, or return -ERROR on error.
+ */
+static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long arg)
+{
+ unsigned long user_bufs;
+ unsigned int nr_slots, size;
+ long ret = 0;
+
+ if (pipe_has_watch_queue(pipe))
+ return -EBUSY;
+
+ size = round_pipe_size(arg);
+ nr_slots = size >> PAGE_SHIFT;
+
+ if (!nr_slots)
+ return -EINVAL;
+
+ /*
+ * If trying to increase the pipe capacity, check that an
+ * unprivileged user is not trying to exceed various limits
+ * (soft limit check here, hard limit check just below).
+ * Decreasing the pipe capacity is always permitted, even
+ * if the user is currently over a limit.
+ */
+ if (nr_slots > pipe->max_usage &&
+ size > pipe_max_size && !capable(CAP_SYS_RESOURCE))
+ return -EPERM;
+
+ user_bufs = account_pipe_buffers(pipe->user, pipe->nr_accounted, nr_slots);
+
+ if (nr_slots > pipe->max_usage &&
+ (too_many_pipe_buffers_hard(user_bufs) ||
+ too_many_pipe_buffers_soft(user_bufs)) &&
+ pipe_is_unprivileged_user()) {
+ ret = -EPERM;
+ goto out_revert_acct;
+ }
+
+ ret = pipe_resize_ring(pipe, nr_slots);
+ if (ret < 0)
+ goto out_revert_acct;
+
+ return pipe->max_usage * PAGE_SIZE;
+
+out_revert_acct:
+ (void) account_pipe_buffers(pipe->user, nr_slots, pipe->nr_accounted);
+ return ret;
+}
+
+/*
+ * Note that i_pipe and i_cdev share the same location, so checking ->i_pipe is
+ * not enough to verify that this is a pipe.
+ */
+struct pipe_inode_info *get_pipe_info(struct file *file, bool for_splice)
+{
+ struct pipe_inode_info *pipe = file->private_data;
+
+ if (file->f_op != &pipefifo_fops || !pipe)
+ return NULL;
+ if (for_splice && pipe_has_watch_queue(pipe))
+ return NULL;
+ return pipe;
+}
+
+long pipe_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
+{
+ struct pipe_inode_info *pipe;
+ long ret;
+
+ pipe = get_pipe_info(file, false);
+ if (!pipe)
+ return -EBADF;
+
+ __pipe_lock(pipe);
+
+ switch (cmd) {
+ case F_SETPIPE_SZ:
+ ret = pipe_set_size(pipe, arg);
+ break;
+ case F_GETPIPE_SZ:
+ ret = pipe->max_usage * PAGE_SIZE;
+ break;
+ default:
+ ret = -EINVAL;
+ break;
+ }
+
+ __pipe_unlock(pipe);
+ return ret;
+}
+
+static const struct super_operations pipefs_ops = {
+ .destroy_inode = free_inode_nonrcu,
+ .statfs = simple_statfs,
+};
+
+/*
+ * pipefs should _never_ be mounted by userland - too much of security hassle,
+ * no real gain from having the whole whorehouse mounted. So we don't need
+ * any operations on the root directory. However, we need a non-trivial
+ * d_name - pipe: will go nicely and kill the special-casing in procfs.
+ */
+
+static int pipefs_init_fs_context(struct fs_context *fc)
+{
+ struct pseudo_fs_context *ctx = init_pseudo(fc, PIPEFS_MAGIC);
+ if (!ctx)
+ return -ENOMEM;
+ ctx->ops = &pipefs_ops;
+ ctx->dops = &pipefs_dentry_operations;
+ return 0;
+}
+
+static struct file_system_type pipe_fs_type = {
+ .name = "pipefs",
+ .init_fs_context = pipefs_init_fs_context,
+ .kill_sb = kill_anon_super,
+};
+
+#ifdef CONFIG_SYSCTL
+static int do_proc_dopipe_max_size_conv(unsigned long *lvalp,
+ unsigned int *valp,
+ int write, void *data)
+{
+ if (write) {
+ unsigned int val;
+
+ val = round_pipe_size(*lvalp);
+ if (val == 0)
+ return -EINVAL;
+
+ *valp = val;
+ } else {
+ unsigned int val = *valp;
+ *lvalp = (unsigned long) val;
+ }
+
+ return 0;
+}
+
+static int proc_dopipe_max_size(struct ctl_table *table, int write,
+ void *buffer, size_t *lenp, loff_t *ppos)
+{
+ return do_proc_douintvec(table, write, buffer, lenp, ppos,
+ do_proc_dopipe_max_size_conv, NULL);
+}
+
+static struct ctl_table fs_pipe_sysctls[] = {
+ {
+ .procname = "pipe-max-size",
+ .data = &pipe_max_size,
+ .maxlen = sizeof(pipe_max_size),
+ .mode = 0644,
+ .proc_handler = proc_dopipe_max_size,
+ },
+ {
+ .procname = "pipe-user-pages-hard",
+ .data = &pipe_user_pages_hard,
+ .maxlen = sizeof(pipe_user_pages_hard),
+ .mode = 0644,
+ .proc_handler = proc_doulongvec_minmax,
+ },
+ {
+ .procname = "pipe-user-pages-soft",
+ .data = &pipe_user_pages_soft,
+ .maxlen = sizeof(pipe_user_pages_soft),
+ .mode = 0644,
+ .proc_handler = proc_doulongvec_minmax,
+ },
+ { }
+};
+#endif
+
+static int __init init_pipe_fs(void)
+{
+ int err = register_filesystem(&pipe_fs_type);
+
+ if (!err) {
+ pipe_mnt = kern_mount(&pipe_fs_type);
+ if (IS_ERR(pipe_mnt)) {
+ err = PTR_ERR(pipe_mnt);
+ unregister_filesystem(&pipe_fs_type);
+ }
+ }
+#ifdef CONFIG_SYSCTL
+ register_sysctl_init("fs", fs_pipe_sysctls);
+#endif
+ return err;
+}
+
+fs_initcall(init_pipe_fs);