netdev - Re: [PATCH] fix for potential NULL pointer dereference with bare lan743x

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Date:   Fri, 30 Oct 2020 17:03:53 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Sergej Bauer <sbauer@...ckbox.su>
Cc:     Bryan Whitehead <bryan.whitehead@...rochip.com>,
        Microchip Linux Driver Support <UNGLinuxDriver@...rochip.com>,
        "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] fix for potential NULL pointer dereference with bare
 lan743x

On Thu, 29 Oct 2020 03:28:45 +0300 Sergej Bauer wrote:
>   This is just a minor fix which prevents a kernel NULL pointer
> dereference when using phy-less lan743x.
> 
> Signed-off-by: Sergej Bauer <sbauer@...ckbox.su>

I take you mean when the device is down netdev->phydev will be NULL?

> diff --git a/drivers/net/ethernet/microchip/lan743x_ethtool.c b/drivers/net/ethernet/microchip/lan743x_ethtool.c
> index dcde496da7fb..354d72d550f2 100644
> --- a/drivers/net/ethernet/microchip/lan743x_ethtool.c
> +++ b/drivers/net/ethernet/microchip/lan743x_ethtool.c
> @@ -793,6 +795,9 @@ static int lan743x_ethtool_set_wol(struct net_device *netdev,
>  {
>  	struct lan743x_adapter *adapter = netdev_priv(netdev);
>  
> +	if (!netdev->phydev)
> +		return -EIO;

Does it make sense to just skip the phy_ethtool_set_wol() call instead?

Also doesn't the wol configuration of the PHY get lost across an
netdev up/down cycle in this driver? Should it be re-applied after phy
is connected back?

>  	adapter->wolopts = 0;
>  	if (wol->wolopts & WAKE_UCAST)
>  		adapter->wolopts |= WAKE_UCAST;