From: Dave Chinner <david@fromorbit.com>
To: "Darrick J. Wong" <darrick.wong@oracle.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>,
Andreas Gruenbacher <agruenba@redhat.com>,
Rasmus Villemoes <linux@rasmusvillemoes.dk>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Bob Peterson <rpeterso@redhat.com>
Subject: Re: [PATCH v3] splice: only read in as much information as there is pipe buffer space
Date: Wed, 16 Oct 2019 14:12:59 +1100 [thread overview]
Message-ID: <20191016031259.GH15134@dread.disaster.area> (raw)
In-Reply-To: <20191014220940.GF13098@magnolia>
On Mon, Oct 14, 2019 at 03:09:40PM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@oracle.com>
>
> Andreas Grünbacher reports that on the two filesystems that support
> iomap directio, it's possible for splice() to return -EAGAIN (instead of
> a short splice) if the pipe being written to has less space available in
> its pipe buffers than the length supplied by the calling process.
>
> Months ago we fixed splice_direct_to_actor to clamp the length of the
> read request to the size of the splice pipe. Do the same to do_splice.
>
> Fixes: 17614445576b6 ("splice: don't read more than available pipe space")
> Reported-by: syzbot+3c01db6025f26530cf8d@syzkaller.appspotmail.com
> Reported-by: Andreas Grünbacher <andreas.gruenbacher@gmail.com>
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> ---
> fs/splice.c | 14 +++++++++++---
> 1 file changed, 11 insertions(+), 3 deletions(-)
>
> diff --git a/fs/splice.c b/fs/splice.c
> index 98412721f056..e509239d7e06 100644
> --- a/fs/splice.c
> +++ b/fs/splice.c
> @@ -945,12 +945,13 @@ ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
> WARN_ON_ONCE(pipe->nrbufs != 0);
>
> while (len) {
> + unsigned int pipe_pages;
define this as a size_t...
> size_t read_len;
> loff_t pos = sd->pos, prev_pos = pos;
>
> /* Don't try to read more the pipe has space for. */
> - read_len = min_t(size_t, len,
> - (pipe->buffers - pipe->nrbufs) << PAGE_SHIFT);
> + pipe_pages = pipe->buffers - pipe->nrbufs;
> + read_len = min(len, (size_t)pipe_pages << PAGE_SHIFT);
read_len = min_t(size_t, len, pipe_pages << PAGER_SHIFT);
> ret = do_splice_to(in, &pos, pipe, read_len, flags);
> if (unlikely(ret <= 0))
> goto out_release;
> @@ -1180,8 +1181,15 @@ static long do_splice(struct file *in, loff_t __user *off_in,
>
> pipe_lock(opipe);
> ret = wait_for_space(opipe, flags);
> - if (!ret)
> + if (!ret) {
> + unsigned int pipe_pages;
> +
> + /* Don't try to read more the pipe has space for. */
> + pipe_pages = opipe->buffers - opipe->nrbufs;
> + len = min(len, (size_t)pipe_pages << PAGE_SHIFT);
And same here...
Cheers,
Dave.
--
Dave Chinner
david@fromorbit.com
next prev parent reply other threads:[~2019-10-16 3:13 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-14 22:09 [PATCH v3] splice: only read in as much information as there is pipe buffer space Darrick J. Wong
2019-10-15 11:31 ` Andreas Grünbacher
2019-10-16 3:12 ` Dave Chinner [this message]
2019-10-16 18:54 ` Darrick J. Wong
2019-10-16 18:45 ` Eric Biggers
2019-10-16 18:52 ` Darrick J. Wong
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