| // 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 |
| * 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; |
| 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, 1); |
| |
| /* |
| * 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; |
| |
| 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, |
| }; |
| |
| 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); |