Bluetooth: Fix potential NULL dereference

The bnep_get_device function may be triggered by an ioctl just after a
connection has gone down. In such a case the respective L2CAP chan->conn
pointer will get set to NULL (by l2cap_chan_del). This patch adds a
missing NULL check for this case in the bnep_get_device() function.
Reported-by: Patrik Flykt <patrik.flykt@linux.intel.com>
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

net/bluetooth/bnep/core.c

@@ -511,13 +511,12 @@ static int bnep_session(void *arg)
 
 static struct device *bnep_get_device(struct bnep_session *session)
 {
-	struct hci_conn *conn;
+	struct l2cap_conn *conn = l2cap_pi(session->sock->sk)->chan->conn;
 
-	conn = l2cap_pi(session->sock->sk)->chan->conn->hcon;
-	if (!conn)
+	if (!conn || !conn->hcon)
 		return NULL;
 
-	return &conn->dev;
+	return &conn->hcon->dev;
 }
 
 static struct device_type bnep_type = {