Bluetooth: Do not dereference zero sk

Signed-off-by: NAndrei Emeltchenko <andrei.emeltchenko@intel.com>
Acked-by: NMarcel Holtmann <marcel@holtmann.org>
Signed-off-by: NJohan Hedberg <johan.hedberg@intel.com>

net/bluetooth/l2cap_sock.c

@@ -795,7 +795,7 @@ static void l2cap_sock_kill(struct sock *sk)
 static int l2cap_sock_shutdown(struct socket *sock, int how)
 {
 	struct sock *sk = sock->sk;
-	struct l2cap_chan *chan = l2cap_pi(sk)->chan;
+	struct l2cap_chan *chan;
 	int err = 0;
 
 	BT_DBG("sock %p, sk %p", sock, sk);
@@ -803,6 +803,8 @@ static int l2cap_sock_shutdown(struct socket *sock, int how)
 	if (!sk)
 		return 0;
 
+	chan = l2cap_pi(sk)->chan;
+
 	lock_sock(sk);
 	if (!sk->sk_shutdown) {
 		if (chan->mode == L2CAP_MODE_ERTM)