Bluetooth: SCO: remove the redundant sco_conn_put

When adding conn, it is necessary to increase and retain the conn reference
count at the same time.

Another problem was fixed along the way, conn_put is missing when hcon is NULL
in the timeout routine.

Fixes: e672077 ("Bluetooth: SCO: Use kref to track lifetime of sco_conn")
Reported-and-tested-by: syzbot+489f78df4709ac2bfdd3@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=489f78df4709ac2bfdd3
Signed-off-by: Edward Adam Davis <eadavis@qq.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>

Author: ea1davis

net/bluetooth/sco.c

@@ -143,6 +143,7 @@ static void sco_sock_timeout(struct work_struct *work)
 	sco_conn_lock(conn);
 	if (!conn->hcon) {
 		sco_conn_unlock(conn);
+		sco_conn_put(conn);
 		return;
 	}
 	sk = sco_sock_hold(conn);
@@ -192,7 +193,6 @@ static struct sco_conn *sco_conn_add(struct hci_conn *hcon)
 			conn->hcon = hcon;
 			sco_conn_unlock(conn);
 		}
-		sco_conn_put(conn);
 		return conn;
 	}