Adding upstream version 5.10.209.upstream/5.10.209upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1454 insertions, 0 deletions

diff --git a/fs/pipe.c b/fs/pipe.c
new file mode 100644
index 000000000..dbb090e1b
--- /dev/null
+++ b/fs/pipe.c
@@ -0,0 +1,1454 @@
+// 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/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
+ */
+unsigned int pipe_max_size = 1048576;
+
+/* Maximum allocatable pages per user. Hard limit is unset by default, soft
+ * matches default values.
+ */
+unsigned long pipe_user_pages_hard;
+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
+ *	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;
+	}
+
+#ifdef CONFIG_WATCH_QUEUE
+	if (pipe->watch_queue) {
+		ret = -EXDEV;
+		goto out;
+	}
+#endif
+
+	/*
+	 * 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;
+	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)
+{
+	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(dentry, 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;
+
+	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;
+
+#ifdef CONFIG_WATCH_QUEUE
+	if (pipe->watch_queue)
+		return -EBUSY;
+#endif
+
+	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;
+
+	pipe->max_usage = nr_slots;
+	pipe->nr_accounted = nr_slots;
+	return pipe->max_usage * PAGE_SIZE;
+
+out_revert_acct:
+	(void) account_pipe_buffers(pipe->user, nr_slots, pipe->nr_accounted);
+	return ret;
+}
+
+/*
+ * After the inode slimming patch, i_pipe/i_bdev/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;
+#ifdef CONFIG_WATCH_QUEUE
+	if (for_splice && pipe->watch_queue)
+		return NULL;
+#endif
+	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,
+};
+
+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);
+		}
+	}
+	return err;
+}
+
+fs_initcall(init_pipe_fs);