> 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.
>
> This is a static checker fix and I'm not sure what the impact is.
>
> Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
>
> diff --git a/drivers/net/ethernet/intel/igbvf/netdev.c b/drivers/net/ethernet/intel/igbvf/netdev.c
> index 95d5430..24e3883 100644
> --- a/drivers/net/ethernet/intel/igbvf/netdev.c
> +++ b/drivers/net/ethernet/intel/igbvf/netdev.c
> @@ -2342,7 +2342,7 @@ static struct net_device_stats *igbvf_get_stats(struct net_device *netdev)
> 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;
> + unsigned 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");
It is safer to check:
if ((new_mtu < 68) || (new_mtu > MAX_JUMBO_FRAME_SIZE - ETH_HLEN - ETH_FCS_LEN)) {
David
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