| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <c6e044cc-5596-90b7-4418-6ad7009d6d79@yandex-team.ru>
Date: Sun, 27 Oct 2019 19:04:35 +0300
From: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
To: David Howells <dhowells@...hat.com>, torvalds@...ux-foundation.org
Cc: Rasmus Villemoes <linux@...musvillemoes.dk>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Peter Zijlstra <peterz@...radead.org>,
nicolas.dichtel@...nd.com, raven@...maw.net,
Christian Brauner <christian@...uner.io>,
keyrings@...r.kernel.org, linux-usb@...r.kernel.org,
linux-block@...r.kernel.org, linux-security-module@...r.kernel.org,
linux-fsdevel@...r.kernel.org, linux-api@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 11/10] pipe: Add fsync() support [ver #2]
On 24/10/2019 19.57, David Howells wrote:
> pipe: Add fsync() support
>
> The keyrings testsuite needs the ability to wait for all the outstanding
> notifications in the queue to have been processed so that it can then go
> through them to find out whether the notifications it expected have been
> emitted.
Similar synchronization is required for reusing memory after vmsplice()?
I don't see other way how sender could safely change these pages.
>
> Implement fsync() support for pipes to provide this. The tailmost buffer
> at the point of calling is marked and fsync adds itself to the list of
> waiters, noting the tail position to be waited for and marking the buffer
> as no longer mergeable. Then when the buffer is consumed, if the flag is
> set, any matching waiters are woken up.
>
> Signed-off-by: David Howells <dhowells@...hat.com>
> ---
> fs/fuse/dev.c | 1
> fs/pipe.c | 61 ++++++++++++++++++++++++++++++++++++++++++++++
> fs/splice.c | 3 ++
> include/linux/pipe_fs_i.h | 22 ++++++++++++++++
> lib/iov_iter.c | 2 -
> 5 files changed, 88 insertions(+), 1 deletion(-)
>
>
> diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
> index 5ef57a322cb8..9617a35579cb 100644
> --- a/fs/fuse/dev.c
> +++ b/fs/fuse/dev.c
> @@ -1983,6 +1983,7 @@ static ssize_t fuse_dev_splice_write(struct pipe_inode_info *pipe,
> if (rem >= ibuf->len) {
> *obuf = *ibuf;
> ibuf->ops = NULL;
> + pipe_wake_fsync(pipe, ibuf, tail);
> tail++;
> pipe_commit_read(pipe, tail);
> } else {
> diff --git a/fs/pipe.c b/fs/pipe.c
> index 6a982a88f658..8e5fd7314be1 100644
> --- a/fs/pipe.c
> +++ b/fs/pipe.c
> @@ -30,6 +30,12 @@
>
> #include "internal.h"
>
> +struct pipe_fsync {
> + struct list_head link; /* Link in pipe->fsync */
> + struct completion done;
> + unsigned int tail; /* The buffer being waited for */
> +};
> +
> /*
> * 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
> @@ -269,6 +275,58 @@ static bool pipe_buf_can_merge(struct pipe_buffer *buf)
> return buf->ops == &anon_pipe_buf_ops;
> }
>
> +/*
> + * Wait for all the data currently in the pipe to be consumed.
> + */
> +static int pipe_fsync(struct file *file, loff_t a, loff_t b, int datasync)
> +{
> + struct pipe_inode_info *pipe = file->private_data;
> + struct pipe_buffer *buf;
> + struct pipe_fsync fsync;
> + unsigned int head, tail, mask;
> +
> + pipe_lock(pipe);
> +
> + head = pipe->head;
> + tail = pipe->tail;
> + mask = pipe->ring_size - 1;
> +
> + if (pipe_empty(head, tail)) {
> + pipe_unlock(pipe);
> + return 0;
> + }
> +
> + init_completion(&fsync.done);
> + fsync.tail = tail;
> + buf = &pipe->bufs[tail & mask];
> + buf->flags |= PIPE_BUF_FLAG_FSYNC;
> + pipe_buf_mark_unmergeable(buf);
> + list_add_tail(&fsync.link, &pipe->fsync);
> + pipe_unlock(pipe);
> +
> + if (wait_for_completion_interruptible(&fsync.done) < 0) {
> + pipe_lock(pipe);
> + list_del(&fsync.link);
> + pipe_unlock(pipe);
> + return -EINTR;
> + }
> +
> + return 0;
> +}
> +
> +void __pipe_wake_fsync(struct pipe_inode_info *pipe, unsigned int tail)
> +{
> + struct pipe_fsync *fsync, *p;
> +
> + list_for_each_entry_safe(fsync, p, &pipe->fsync, link) {
> + if (fsync->tail == tail) {
> + list_del_init(&fsync->link);
> + complete(&fsync->done);
> + }
> + }
> +}
> +EXPORT_SYMBOL(__pipe_wake_fsync);
> +
> static ssize_t
> pipe_read(struct kiocb *iocb, struct iov_iter *to)
> {
> @@ -325,6 +383,7 @@ pipe_read(struct kiocb *iocb, struct iov_iter *to)
> if (!buf->len) {
> pipe_buf_release(pipe, buf);
> spin_lock_irq(&pipe->wait.lock);
> + pipe_wake_fsync(pipe, buf, tail);
> tail++;
> pipe_commit_read(pipe, tail);
> do_wakeup = 1;
> @@ -717,6 +776,7 @@ struct pipe_inode_info *alloc_pipe_info(void)
> pipe->ring_size = pipe_bufs;
> pipe->user = user;
> mutex_init(&pipe->mutex);
> + INIT_LIST_HEAD(&pipe->fsync);
> return pipe;
> }
>
> @@ -1060,6 +1120,7 @@ const struct file_operations pipefifo_fops = {
> .llseek = no_llseek,
> .read_iter = pipe_read,
> .write_iter = pipe_write,
> + .fsync = pipe_fsync,
> .poll = pipe_poll,
> .unlocked_ioctl = pipe_ioctl,
> .release = pipe_release,
> diff --git a/fs/splice.c b/fs/splice.c
> index 3f72bc31b6ec..e106367e1be6 100644
> --- a/fs/splice.c
> +++ b/fs/splice.c
> @@ -523,6 +523,7 @@ static int splice_from_pipe_feed(struct pipe_inode_info *pipe, struct splice_des
>
> if (!buf->len) {
> pipe_buf_release(pipe, buf);
> + pipe_wake_fsync(pipe, buf, tail);
> tail++;
> pipe_commit_read(pipe, tail);
> if (pipe->files)
> @@ -771,6 +772,7 @@ iter_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
> ret -= buf->len;
> buf->len = 0;
> pipe_buf_release(pipe, buf);
> + pipe_wake_fsync(pipe, buf, tail);
> tail++;
> pipe_commit_read(pipe, tail);
> if (pipe->files)
> @@ -1613,6 +1615,7 @@ static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
> */
> *obuf = *ibuf;
> ibuf->ops = NULL;
> + pipe_wake_fsync(ipipe, ibuf, i_tail);
> i_tail++;
> pipe_commit_read(ipipe, i_tail);
> input_wakeup = true;
> diff --git a/include/linux/pipe_fs_i.h b/include/linux/pipe_fs_i.h
> index 90055ff16550..1a3027089558 100644
> --- a/include/linux/pipe_fs_i.h
> +++ b/include/linux/pipe_fs_i.h
> @@ -8,6 +8,7 @@
> #define PIPE_BUF_FLAG_ATOMIC 0x02 /* was atomically mapped */
> #define PIPE_BUF_FLAG_GIFT 0x04 /* page is a gift */
> #define PIPE_BUF_FLAG_PACKET 0x08 /* read() as a packet */
> +#define PIPE_BUF_FLAG_FSYNC 0x10 /* fsync() is waiting for this buffer to die */
>
> /**
> * struct pipe_buffer - a linux kernel pipe buffer
> @@ -43,6 +44,7 @@ struct pipe_buffer {
> * @w_counter: writer counter
> * @fasync_readers: reader side fasync
> * @fasync_writers: writer side fasync
> + * @fsync: Waiting fsyncs
> * @bufs: the circular array of pipe buffers
> * @user: the user who created this pipe
> **/
> @@ -62,6 +64,7 @@ struct pipe_inode_info {
> struct page *tmp_page;
> struct fasync_struct *fasync_readers;
> struct fasync_struct *fasync_writers;
> + struct list_head fsync;
> struct pipe_buffer *bufs;
> struct user_struct *user;
> };
> @@ -268,6 +271,25 @@ extern const struct pipe_buf_operations nosteal_pipe_buf_ops;
> long pipe_fcntl(struct file *, unsigned int, unsigned long arg);
> struct pipe_inode_info *get_pipe_info(struct file *file);
>
> +void __pipe_wake_fsync(struct pipe_inode_info *pipe, unsigned int tail);
> +
> +/**
> + * pipe_wake_fsync - Wake up anyone waiting with fsync for this point
> + * @pipe: The pipe that owns the buffer
> + * @buf: The pipe buffer in question
> + * @tail: The index in the ring of the buffer
> + *
> + * Check to see if anyone is waiting for the pipe ring to clear up to and
> + * including this buffer, and, if they are, wake them up.
> + */
> +static inline void pipe_wake_fsync(struct pipe_inode_info *pipe,
> + struct pipe_buffer *buf,
> + unsigned int tail)
> +{
> + if (unlikely(buf->flags & PIPE_BUF_FLAG_FSYNC))
> + __pipe_wake_fsync(pipe, tail);
> +}
> +
> int create_pipe_files(struct file **, int);
> unsigned int round_pipe_size(unsigned long size);
>
> diff --git a/lib/iov_iter.c b/lib/iov_iter.c
> index e22f4e283f6d..38d52524cd21 100644
> --- a/lib/iov_iter.c
> +++ b/lib/iov_iter.c
> @@ -404,7 +404,7 @@ static size_t copy_page_to_iter_pipe(struct page *page, size_t offset, size_t by
> buf->offset = offset;
> buf->len = bytes;
>
> - pipe_commit_read(pipe, i_head);
> + pipe_commit_write(pipe, i_head);
> i->iov_offset = offset + bytes;
> i->head = i_head;
> out:
>
>
Powered by blists - more mailing lists