linux-stable/fs/pipe.c
Linus Torvalds a05aea98d4 sysctl-6.8-rc1
To help make the move of sysctls out of kernel/sysctl.c not incur a size
 penalty sysctl has been changed to allow us to not require the sentinel, the
 final empty element on the sysctl array. Joel Granados has been doing all this
 work. On the v6.6 kernel we got the major infrastructure changes required to
 support this. For v6.7 we had all arch/ and drivers/ modified to remove
 the sentinel. For v6.8-rc1 we get a few more updates for fs/ directory only.
 The kernel/ directory is left but we'll save that for v6.9-rc1 as those patches
 are still being reviewed. After that we then can expect also the removal of the
 no longer needed check for procname == NULL.
 
 Let us recap the purpose of this work:
 
   - this helps reduce the overall build time size of the kernel and run time
     memory consumed by the kernel by about ~64 bytes per array
   - the extra 64-byte penalty is no longer inncurred now when we move sysctls
     out from kernel/sysctl.c to their own files
 
 Thomas Weißschuh also sent a few cleanups, for v6.9-rc1 we expect to see further
 work by Thomas Weißschuh with the constificatin of the struct ctl_table.
 
 Due to Joel Granados's work, and to help bring in new blood, I have suggested
 for him to become a maintainer and he's accepted. So for v6.9-rc1 I look forward
 to seeing him sent you a pull request for further sysctl changes. This also
 removes Iurii Zaikin as a maintainer as he has moved on to other projects and
 has had no time to help at all.
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Merge tag 'sysctl-6.8-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/mcgrof/linux

Pull sysctl updates from Luis Chamberlain:
 "To help make the move of sysctls out of kernel/sysctl.c not incur a
  size penalty sysctl has been changed to allow us to not require the
  sentinel, the final empty element on the sysctl array. Joel Granados
  has been doing all this work.

  In the v6.6 kernel we got the major infrastructure changes required to
  support this. For v6.7 we had all arch/ and drivers/ modified to
  remove the sentinel. For v6.8-rc1 we get a few more updates for fs/
  directory only.

  The kernel/ directory is left but we'll save that for v6.9-rc1 as
  those patches are still being reviewed. After that we then can expect
  also the removal of the no longer needed check for procname == NULL.

  Let us recap the purpose of this work:

   - this helps reduce the overall build time size of the kernel and run
     time memory consumed by the kernel by about ~64 bytes per array

   - the extra 64-byte penalty is no longer inncurred now when we move
     sysctls out from kernel/sysctl.c to their own files

  Thomas Weißschuh also sent a few cleanups, for v6.9-rc1 we expect to
  see further work by Thomas Weißschuh with the constificatin of the
  struct ctl_table.

  Due to Joel Granados's work, and to help bring in new blood, I have
  suggested for him to become a maintainer and he's accepted. So for
  v6.9-rc1 I look forward to seeing him sent you a pull request for
  further sysctl changes. This also removes Iurii Zaikin as a maintainer
  as he has moved on to other projects and has had no time to help at
  all"

* tag 'sysctl-6.8-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/mcgrof/linux:
  sysctl: remove struct ctl_path
  sysctl: delete unused define SYSCTL_PERM_EMPTY_DIR
  coda: Remove the now superfluous sentinel elements from ctl_table array
  sysctl: Remove the now superfluous sentinel elements from ctl_table array
  fs: Remove the now superfluous sentinel elements from ctl_table array
  cachefiles: Remove the now superfluous sentinel element from ctl_table array
  sysclt: Clarify the results of selftest run
  sysctl: Add a selftest for handling empty dirs
  sysctl: Fix out of bounds access for empty sysctl registers
  MAINTAINERS: Add Joel Granados as co-maintainer for proc sysctl
  MAINTAINERS: remove Iurii Zaikin from proc sysctl
2024-01-10 17:44:36 -08:00

1530 lines
37 KiB
C

// 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 inline unsigned int pipe_update_tail(struct pipe_inode_info *pipe,
struct pipe_buffer *buf,
unsigned int tail)
{
pipe_buf_release(pipe, buf);
/*
* If the pipe has a watch_queue, we need additional protection
* by the spinlock because notifications get posted with only
* this spinlock, no mutex
*/
if (pipe_has_watch_queue(pipe)) {
spin_lock_irq(&pipe->rd_wait.lock);
#ifdef CONFIG_WATCH_QUEUE
if (buf->flags & PIPE_BUF_FLAG_LOSS)
pipe->note_loss = true;
#endif
pipe->tail = ++tail;
spin_unlock_irq(&pipe->rd_wait.lock);
return tail;
}
/*
* Without a watch_queue, we can simply increment the tail
* without the spinlock - the mutex is enough.
*/
pipe->tail = ++tail;
return tail;
}
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)
tail = pipe_update_tail(pipe, buf, tail);
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) ||
(iocb->ki_flags & IOCB_NOWAIT)) {
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;
/*
* Reject writing to watch queue pipes before the point where we lock
* the pipe.
* Otherwise, lockdep would be unhappy if the caller already has another
* pipe locked.
* If we had to support locking a normal pipe and a notification pipe at
* the same time, we could set up lockdep annotations for that, but
* since we don't actually need that, it's simpler to just bail here.
*/
if (pipe_has_watch_queue(pipe))
return -EXDEV;
/* 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 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;
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.
*/
pipe->head = head + 1;
/* 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->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) ||
(iocb->ki_flags & IOCB_NOWAIT)) {
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 __ro_after_init;
/*
* 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();
simple_inode_init_ts(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;
/* pipe groks IOCB_NOWAIT */
files[0]->f_mode |= FMODE_NOWAIT;
files[1]->f_mode |= FMODE_NOWAIT;
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 int 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 int 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 int 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);