linux-kernel - [PATCH 3.16 044/202] fuse: call pipe_buf

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Message-ID: <lsq.1556377989.28395121@decadent.org.uk>
Date:   Sat, 27 Apr 2019 16:13:09 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "Miklos Szeredi" <mszeredi@...hat.com>,
        "Jann Horn" <jannh@...gle.com>
Subject: [PATCH 3.16 044/202] fuse: call pipe_buf_release() under pipe lock

3.16.66-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Jann Horn <jannh@...gle.com>

commit 9509941e9c534920ccc4771ae70bd6cbbe79df1c upstream.

Some of the pipe_buf_release() handlers seem to assume that the pipe is
locked - in particular, anon_pipe_buf_release() accesses pipe->tmp_page
without taking any extra locks. From a glance through the callers of
pipe_buf_release(), it looks like FUSE is the only one that calls
pipe_buf_release() without having the pipe locked.

This bug should only lead to a memory leak, nothing terrible.

Fixes: dd3bb14f44a6 ("fuse: support splice() writing to fuse device")
Signed-off-by: Jann Horn <jannh@...gle.com>
Signed-off-by: Miklos Szeredi <mszeredi@...hat.com>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 fs/fuse/dev.c | 2 ++
 1 file changed, 2 insertions(+)

--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -1978,10 +1978,12 @@ static ssize_t fuse_dev_splice_write(str
 
 	ret = fuse_dev_do_write(fc, &cs, len);
 
+	pipe_lock(pipe);
 	for (idx = 0; idx < nbuf; idx++) {
 		struct pipe_buffer *buf = &bufs[idx];
 		buf->ops->release(pipe, buf);
 	}
+	pipe_unlock(pipe);
 out:
 	kfree(bufs);
 	return ret;