Bluetooth: l2cap: always unlock channel in l2cap_conless_channel()

[ Upstream commit c531e63871c0b50c8c4e62c048535a08886fba3e ]

Add missing call to 'l2cap_chan_unlock()' on receive error handling
path in 'l2cap_conless_channel()'.

Fixes: a24cce144b ("Bluetooth: Fix reference counting of global L2CAP channels")
Reported-by: syzbot+45ac74737e866894acb0@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=45ac74737e866894acb0
Signed-off-by: Dmitry Antipov <dmantipov@yandex.ru>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

net/bluetooth/l2cap_core.c

@@ -7767,6 +7767,7 @@ static void l2cap_conless_channel(struct l2cap_conn *conn, __le16 psm,
 	bt_cb(skb)->l2cap.psm = psm;
 
 	if (!chan->ops->recv(chan, skb)) {
+		l2cap_chan_unlock(chan);
 		l2cap_chan_put(chan);
 		return;
 	}