kernel/relay.c: revert "kernel/relay.c: fix potential memory leak"

This reverts commit ba62baf ("kernel/relay.c: fix potential memory leak").

This commit introduced a double free bug, because 'chan' is already
freed by the line:

    kref_put(&chan->kref, relay_destroy_channel);

This bug was found by syzkaller, using the BLKTRACESETUP ioctl.

Link: http://lkml.kernel.org/r/[email protected]
Fixes: ba62baf ("kernel/relay.c: fix potential memory leak")
Signed-off-by: Eric Biggers <[email protected]>
Reported-by: syzbot <[email protected]>
Reviewed-by: Andrew Morton <[email protected]>
Cc: Zhouyi Zhou <[email protected]>
Cc: Jens Axboe <[email protected]>
Cc: <[email protected]>	[4.7+]
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

kernel/relay.c

@@ -611,7 +611,6 @@ struct rchan *relay_open(const char *base_filename,
 
 	kref_put(&chan->kref, relay_destroy_channel);
 	mutex_unlock(&relay_channels_mutex);
-	kfree(chan);
 	return NULL;
 }
 EXPORT_SYMBOL_GPL(relay_open);