Bluetooth: smp: Fix possible NULL dereference

smp_chan_create might return NULL so we need to check before
dereferencing smp.
Signed-off-by: Andrei Emeltchenko <andrei.emeltchenko@intel.com>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>

net/bluetooth/smp.c

@@ -579,9 +579,12 @@ static u8 smp_cmd_pairing_req(struct l2cap_conn *conn, struct sk_buff *skb)
 
 	if (!test_and_set_bit(HCI_CONN_LE_SMP_PEND, &conn->hcon->flags))
 		smp = smp_chan_create(conn);
-
+	else
 		smp = conn->smp_chan;
 
+	if (!smp)
+		return SMP_UNSPECIFIED;
+
 	smp->preq[0] = SMP_CMD_PAIRING_REQ;
 	memcpy(&smp->preq[1], req, sizeof(*req));
 	skb_pull(skb, sizeof(*req));