diff options
Diffstat (limited to 'fs/pipe.c')
| -rw-r--r-- | fs/pipe.c | 1454 |
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); |