kernel/relay.c: fix potential memory leak

When relay_open_buf() fails in relay_open(), code will goto free_bufs,
but chan is nowhere freed.

Link: http://lkml.kernel.org/r/1464777927-19675-1-git-send-email-yizhouzhou@ict.ac.cn
Signed-off-by: Zhouyi Zhou <zhouzhouyi@gmail.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/relay.c

@@ -614,6 +614,7 @@ free_bufs:
 
 	kref_put(&chan->kref, relay_destroy_channel);
 	mutex_unlock(&relay_channels_mutex);
+	kfree(chan);
 	return NULL;
 }
 EXPORT_SYMBOL_GPL(relay_open);