[PATCH 4.9 116/137] fuse: call pipe_buf_release() under pipe lock

From: Greg Kroah-Hartman
Date: Mon Feb 11 2019 - 10:11:03 EST

4.9-stable review patch. If anyone has any objections, please let me know.


From: Jann Horn <jannh@xxxxxxxxxx>

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")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Jann Horn <jannh@xxxxxxxxxx>
Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

fs/fuse/dev.c | 2 ++
1 file changed, 2 insertions(+)

--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -2018,8 +2018,10 @@ static ssize_t fuse_dev_splice_write(str

ret = fuse_dev_do_write(fud, &cs, len);

+ pipe_lock(pipe);
for (idx = 0; idx < nbuf; idx++)
pipe_buf_release(pipe, &bufs[idx]);
+ pipe_unlock(pipe);