[PATCH 4.4 085/143] fuse: call pipe_buf_release() under pipe lock

[Greg Kroah-Hartman]

4.4-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 |    3 +++
 1 file changed, 3 insertions(+)

--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -2074,10 +2074,13 @@ 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++) {
 		struct pipe_buffer *buf = &bufs[idx];
 		buf->ops->release(pipe, buf);
 	}
+	pipe_unlock(pipe);
+
 out:
 	kfree(bufs);
 	return ret;