igbvf: integer wrapping bug setting the mtu

If new_mtu is very large then "new_mtu + ETH_HLEN + ETH_FCS_LEN" can
wrap and the check on the next line can underflow. This is one of those
bugs which can be triggered by the user if you have namespaces
configured.

Also since this is something the user can trigger then we don't want to
have dev_err() message.

This is a static checker fix and I'm not sure what the impact is.
Signed-off-by: NDan Carpenter <dan.carpenter@oracle.com>
Tested-by: NAaron Brown <aaron.f.brown@intel.com>
Tested-by: Sibai Li Sibai.li@intel.com>
Signed-off-by: NJeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/igbvf/netdev.c

@@ -2343,10 +2343,9 @@ static int igbvf_change_mtu(struct net_device *netdev, int new_mtu)
 	struct igbvf_adapter *adapter = netdev_priv(netdev);
 	int max_frame = new_mtu + ETH_HLEN + ETH_FCS_LEN;
 
-	if ((new_mtu < 68) || (max_frame > MAX_JUMBO_FRAME_SIZE)) {
-		dev_err(&adapter->pdev->dev, "Invalid MTU setting\n");
+	if (new_mtu < 68 || new_mtu > INT_MAX - ETH_HLEN - ETH_FCS_LEN ||
+	    max_frame > MAX_JUMBO_FRAME_SIZE)
 		return -EINVAL;
-	}
 
 #define MAX_STD_JUMBO_FRAME_SIZE 9234
 	if (max_frame > MAX_STD_JUMBO_FRAME_SIZE) {