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(I'm so sorry!) Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel os linux
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SPDX-License-Identifier: GPL-2.0/* * linux/fs/pipe.c * * Copyright (C) 1991, 1992, 1999 Linus Torvalds */
#include <linux/mm.h>#include <linux/file.h>#include <linux/poll.h>#include <linux/slab.h>#include <linux/module.h>#include <linux/init.h>#include <linux/fs.h>#include <linux/log2.h>#include <linux/mount.h>#include <linux/pseudo_fs.h>#include <linux/magic.h>#include <linux/pipe_fs_i.h>#include <linux/uio.h>#include <linux/highmem.h>#include <linux/pagemap.h>#include <linux/audit.h>#include <linux/syscalls.h>#include <linux/fcntl.h>#include <linux/memcontrol.h>#include <linux/watch_queue.h>#include <linux/sysctl.h>#include <linux/sort.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 */
#ifdef CONFIG_PROVE_LOCKINGstatic int pipe_lock_cmp_fn(const struct lockdep_map *a, const struct lockdep_map *b){ return cmp_int((unsigned long) a, (unsigned long) b);}#endif
void pipe_lock(struct pipe_inode_info *pipe){ if (pipe->files) mutex_lock(&pipe->mutex);}EXPORT_SYMBOL(pipe_lock);
void pipe_unlock(struct pipe_inode_info *pipe){ if (pipe->files) mutex_unlock(&pipe->mutex);}EXPORT_SYMBOL(pipe_unlock);
void pipe_double_lock(struct pipe_inode_info *pipe1, struct pipe_inode_info *pipe2){ BUG_ON(pipe1 == pipe2);
if (pipe1 > pipe2) swap(pipe1, pipe2);
pipe_lock(pipe1); pipe_lock(pipe2);}
static struct page *anon_pipe_prealloc_pop(struct anon_pipe_prealloc *prealloc){ if (!prealloc->count) return NULL;
prealloc->count--;
return prealloc->pages[prealloc->count];}
/* Push a page to the prealloc pool. Returns true if added, false if full. */static bool anon_pipe_prealloc_push(struct anon_pipe_prealloc *prealloc, struct page *page){ if (prealloc->count >= PIPE_PREALLOC_MAX) return false; prealloc->pages[prealloc->count++] = page; return true;}
/* * Top up the pipe's own pool, then take pipe->mutex and return with it held. * The shortfall is allocated outside the lock; the push and the caller's write * then run under a single lock acquisition, avoiding a separate prefill * lock/unlock cycle. anon_pipe_get_page() drains the pool instead of allocating * under the lock. */static void anon_pipe_prefill_and_lock(struct pipe_inode_info *pipe, size_t total_len){ struct page *pages[PIPE_PREALLOC_MAX]; unsigned int want, have, need, n = 0;
want = min_t(unsigned int, DIV_ROUND_UP(total_len, PAGE_SIZE), PIPE_PREALLOC_MAX); /* Unlocked read; the pool is refilled under the lock below. */ have = min_t(unsigned int, READ_ONCE(pipe->prealloc.count), want); need = want - have;
if (!need) { mutex_lock(&pipe->mutex); return; }
while (n < need) { struct page *page = alloc_page(GFP_HIGHUSER | __GFP_ACCOUNT);
if (!page) break; pages[n++] = page; }
mutex_lock(&pipe->mutex); while (n && anon_pipe_prealloc_push(&pipe->prealloc, pages[n - 1])) n--;
/* * Just flush any extra page that got affected by the TOCTOU * effect */ while (n) put_page(pages[--n]);}
/* * Called with pipe->mutex held. Trim the pool down to PIPE_PREALLOC_KEEP under * the lock, drop it, then free the excess outside the critical section. */static void anon_pipe_trim_and_unlock(struct pipe_inode_info *pipe){ struct page *excess[PIPE_PREALLOC_MAX]; unsigned int nexcess = 0;
while (pipe->prealloc.count > PIPE_PREALLOC_KEEP) excess[nexcess++] = anon_pipe_prealloc_pop(&pipe->prealloc); mutex_unlock(&pipe->mutex);
while (nexcess) put_page(excess[--nexcess]);}
static struct page *anon_pipe_get_page(struct pipe_inode_info *pipe){ struct page *page;
/* Drain the prealloc pool before allocating. Called with mutex held. */ page = anon_pipe_prealloc_pop(&pipe->prealloc); if (page) return page;
/* FWIW: This is called with pipe->mutex held */ return alloc_page(GFP_HIGHUSER | __GFP_ACCOUNT);}
static void anon_pipe_put_page(struct pipe_inode_info *pipe, struct page *page){ if (page_count(page) == 1 && anon_pipe_prealloc_push(&pipe->prealloc, page)) return;
put_page(page);}
static void anon_pipe_buf_release(struct pipe_inode_info *pipe, struct pipe_buffer *buf){ struct page *page = buf->page;
anon_pipe_put_page(pipe, 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){ union pipe_index idx = { .head_tail = READ_ONCE(pipe->head_tail) }; unsigned int writers = READ_ONCE(pipe->writers);
return !pipe_empty(idx.head, idx.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_tanon_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 wake_writer = false, wake_next_reader = false; ssize_t ret;
/* Null read succeeds. */ if (unlikely(total_len == 0)) return 0;
ret = 0; mutex_lock(&pipe->mutex);
/* * We only wake up writers if the pipe was full when we started reading * and it is no longer full after reading 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. */ for (;;) { /* Read ->head with a barrier vs post_one_notification() */ unsigned int head = smp_load_acquire(&pipe->head); unsigned int tail = pipe->tail;
#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_buf(pipe, tail); 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) { wake_writer |= pipe_full(head, tail, pipe->max_usage); 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; } mutex_unlock(&pipe->mutex); /* * We only get here if we didn't actually read anything. * * 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;
wake_next_reader = true; mutex_lock(&pipe->mutex); } if (pipe_is_empty(pipe)) wake_next_reader = false; /* Consumed buffers may have refilled the pool; trim it and unlock. */ anon_pipe_trim_and_unlock(pipe);
if (wake_writer) 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); return ret;}
static ssize_tfifo_pipe_read(struct kiocb *iocb, struct iov_iter *to){ int ret = anon_pipe_read(iocb, to); if (ret > 0) file_accessed(iocb->ki_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){ union pipe_index idx = { .head_tail = READ_ONCE(pipe->head_tail) }; unsigned int max_usage = READ_ONCE(pipe->max_usage);
return !pipe_full(idx.head, idx.tail, max_usage) || !READ_ONCE(pipe->readers);}
static ssize_tanon_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;
anon_pipe_prefill_and_lock(pipe, total_len);
if (!pipe->readers) { if ((iocb->ki_flags & IOCB_NOSIGNAL) == 0) 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) { struct pipe_buffer *buf = pipe_buf(pipe, head - 1); 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) { if ((iocb->ki_flags & IOCB_NOSIGNAL) == 0) send_sig(SIGPIPE, current, 0); if (!ret) ret = -EPIPE; break; }
head = pipe->head; if (!pipe_full(head, pipe->tail, pipe->max_usage)) { struct pipe_buffer *buf; struct page *page; int copied;
page = anon_pipe_get_page(pipe); if (unlikely(!page)) { if (!ret) ret = -ENOMEM; break; }
copied = copy_page_from_iter(page, 0, PAGE_SIZE, from); if (unlikely(copied < PAGE_SIZE && iov_iter_count(from))) { anon_pipe_put_page(pipe, page); if (!ret) ret = -EFAULT; break; }
pipe->head = head + 1; /* Insert it into the buffer array */ buf = pipe_buf(pipe, head); buf->page = page; buf->ops = &anon_pipe_buf_ops; buf->offset = 0; if (is_packetized(filp)) buf->flags = PIPE_BUF_FLAG_PACKET; else buf->flags = PIPE_BUF_FLAG_CAN_MERGE;
buf->len = copied; ret += copied;
if (!iov_iter_count(from)) break;
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. */ mutex_unlock(&pipe->mutex); 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)); mutex_lock(&pipe->mutex); was_empty = pipe_is_empty(pipe); wake_next_writer = true; }out: if (pipe_is_full(pipe)) wake_next_writer = false; anon_pipe_trim_and_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 * * ->pseudo_edgetrigger enables per-write wakeups, see pipe_poll() */ if (was_empty || READ_ONCE(pipe->pseudo_edgetrigger)) 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); return ret;}
static ssize_tfifo_pipe_write(struct kiocb *iocb, struct iov_iter *from){ int ret = anon_pipe_write(iocb, from); if (ret > 0) { struct file *filp = iocb->ki_filp; if (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;
switch (cmd) { case FIONREAD: mutex_lock(&pipe->mutex); count = 0; head = pipe->head; tail = pipe->tail;
while (!pipe_empty(head, tail)) { count += pipe_buf(pipe, tail)->len; tail++; } mutex_unlock(&pipe->mutex);
return put_user(count, (int __user *)arg);
#ifdef CONFIG_WATCH_QUEUE case IOC_WATCH_QUEUE_SET_SIZE: { int ret; mutex_lock(&pipe->mutex); ret = watch_queue_set_size(pipe, arg); mutex_unlock(&pipe->mutex); return ret; }
case IOC_WATCH_QUEUE_SET_FILTER: return watch_queue_set_filter( pipe, (struct watch_notification_filter __user *)arg);#endif
default: return -ENOIOCTLCMD; }}
static __poll_tpipe_poll(struct file *filp, poll_table *wait){ __poll_t mask; struct pipe_inode_info *pipe = filp->private_data; union pipe_index idx;
/* * Legacy epoll(EPOLLET) users depend on historical per-write wakeups, * see 3a34b13a88ca ("pipe: make pipe writes always wake up readers") * and the ->pseudo_edgetrigger check in anon_pipe_write(). * Currently io_uring sets EPOLLET for multishot polls, so it gets the * same behaviour. */ if ((filp->f_mode & FMODE_READ) && wait && (wait->_key & EPOLLET) && unlikely(!READ_ONCE(pipe->pseudo_edgetrigger))) WRITE_ONCE(pipe->pseudo_edgetrigger, 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. */ idx.head_tail = READ_ONCE(pipe->head_tail);
mask = 0; if (filp->f_mode & FMODE_READ) { if (!pipe_empty(idx.head, idx.tail)) mask |= EPOLLIN | EPOLLRDNORM; if (!pipe->writers && filp->f_pipe != pipe->w_counter) mask |= EPOLLHUP; }
if (filp->f_mode & FMODE_WRITE) { if (!pipe_full(idx.head, idx.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 intpipe_release(struct inode *inode, struct file *file){ struct pipe_inode_info *pipe = file->private_data;
mutex_lock(&pipe->mutex); 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); } mutex_unlock(&pipe->mutex);
put_pipe_info(inode, pipe); return 0;}
static intpipe_fasync(int fd, struct file *filp, int on){ struct pipe_inode_info *pipe = filp->private_data; int retval = 0;
mutex_lock(&pipe->mutex); if (filp->f_mode & FMODE_READ) retval = fasync_helper(fd, filp, on, &pipe->fasync_readers); if ((filp->f_mode & FMODE_WRITE) && retval >= 0) { int read_ret = retval;
retval = fasync_helper(fd, filp, on, &pipe->fasync_writers); /* Undo only a reader entry added by this call. */ if (retval < 0 && read_ret > 0) fasync_helper(-1, filp, 0, &pipe->fasync_readers); } mutex_unlock(&pipe->mutex); 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_obj(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 = kzalloc_objs(struct pipe_buffer, pipe_bufs, 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); lock_set_cmp_fn(&pipe->mutex, pipe_lock_cmp_fn, NULL); 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 for (i = 0; i < pipe->prealloc.count; i++) __free_page(pipe->prealloc.pages[i]); 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:[%llu]", d_inode(dentry)->i_ino);}
static const struct dentry_operations pipefs_dentry_operations = { .d_dname = pipefs_dname,};
static const struct file_operations pipeanon_fops;
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 = &pipeanon_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_state_assign_raw(inode, 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)), &pipeanon_fops); if (IS_ERR(f)) { free_pipe_info(inode->i_pipe); iput(inode); return PTR_ERR(f); }
f->private_data = inode->i_pipe; f->f_pipe = 0;
res[0] = alloc_file_clone(f, O_RDONLY | (flags & O_NONBLOCK), &pipeanon_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[0]->f_pipe = 0; res[1] = f; stream_open(inode, res[0]); stream_open(inode, res[1]);
/* pipe groks IOCB_NOWAIT */ res[0]->f_mode |= FMODE_NOWAIT; res[1]->f_mode |= FMODE_NOWAIT;
/* * Disable permission and pre-content events, but enable legacy * inotify events for legacy users. */ file_set_fsnotify_mode(res[0], FMODE_NONOTIFY_PERM); file_set_fsnotify_mode(res[1], FMODE_NONOTIFY_PERM); 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){ bool is_pipe = inode->i_fop == &pipeanon_fops; struct pipe_inode_info *pipe; int ret;
filp->f_pipe = 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 */
mutex_lock(&pipe->mutex);
/* 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_pipe = 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! */ mutex_unlock(&pipe->mutex); 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: mutex_unlock(&pipe->mutex);
put_pipe_info(inode, pipe); return ret;}
const struct file_operations pipefifo_fops = { .open = fifo_open, .read_iter = fifo_pipe_read, .write_iter = fifo_pipe_write, .poll = pipe_poll, .unlocked_ioctl = pipe_ioctl, .release = pipe_release, .fasync = pipe_fasync, .splice_write = iter_file_splice_write,};
static const struct file_operations pipeanon_fops = { .open = fifo_open, .read_iter = anon_pipe_read, .write_iter = anon_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;
/* nr_slots larger than limits of pipe->{head,tail} */ if (unlikely(nr_slots > (pipe_index_t)-1u)) return -EINVAL;
bufs = kzalloc_objs(*bufs, nr_slots, 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_poll(&pipe->wr_wait, EPOLLOUT | EPOLLWRNORM); 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 (!pipe) return NULL; if (file->f_op != &pipefifo_fops && file->f_op != &pipeanon_fops) 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;
mutex_lock(&pipe->mutex);
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; }
mutex_unlock(&pipe->mutex); 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 file system 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 ulong round_pipe_size_ul(ulong size){ return round_pipe_size(size);}
static int u2k_pipe_maxsz(const ulong *u_ptr, uint *k_ptr){ return proc_uint_u2k_conv_uop(u_ptr, k_ptr, round_pipe_size_ul);}
static int do_proc_uint_conv_pipe_maxsz(bool *negp, ulong *u_ptr, uint *k_ptr, int dir, const struct ctl_table *table){ return proc_uint_conv(u_ptr, k_ptr, dir, table, true, u2k_pipe_maxsz, proc_uint_k2u_conv);}
static int proc_dopipe_max_size(const struct ctl_table *table, int write, void *buffer, size_t *lenp, loff_t *ppos){ return proc_douintvec_conv(table, write, buffer, lenp, ppos, do_proc_uint_conv_pipe_maxsz);}
static const 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, .extra1 = SYSCTL_ONE, }, { .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);