Re: [PATCH v1 2/2] net: ethernet: mtk_eth_soc: Support custom ifname

From: "Russell King (Oracle)" <linux@armlinux.org.uk>
To: Reto Schneider <code@reto-schneider.ch>
Cc: devicetree@vger.kernel.org, linux-mediatek@lists.infradead.org,
	netdev@vger.kernel.org, Stefan Roese <sr@denx.de>,
	Reto Schneider <reto.schneider@husqvarnagroup.com>,
	"David S. Miller" <davem@davemloft.net>,
	Felix Fietkau <nbd@nbd.name>, Jakub Kicinski <kuba@kernel.org>,
	John Crispin <john@phrozen.org>,
	Mark Lee <Mark-MC.Lee@mediatek.com>,
	Matthias Brugger <matthias.bgg@gmail.com>,
	Sean Wang <sean.wang@mediatek.com>,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v1 2/2] net: ethernet: mtk_eth_soc: Support custom ifname
Date: Sun, 13 Jun 2021 13:20:43 +0100	[thread overview]
Message-ID: <20210613122043.GP22278@shell.armlinux.org.uk> (raw)
In-Reply-To: <20210613115820.1525478-2-code@reto-schneider.ch>

On Sun, Jun 13, 2021 at 01:58:19PM +0200, Reto Schneider wrote:
> diff --git a/drivers/net/ethernet/mediatek/mtk_eth_soc.c b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
> index 64adfd24e134..8bb09801918f 100644
> --- a/drivers/net/ethernet/mediatek/mtk_eth_soc.c
> +++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
> @@ -2948,6 +2948,7 @@ static const struct net_device_ops mtk_netdev_ops = {
>  static int mtk_add_mac(struct mtk_eth *eth, struct device_node *np)
>  {
>  	const __be32 *_id = of_get_property(np, "reg", NULL);
> +	const char *const name = of_get_property(np, "label", NULL);
>  	phy_interface_t phy_mode;
>  	struct phylink *phylink;
>  	struct mtk_mac *mac;
> @@ -3020,6 +3021,9 @@ static int mtk_add_mac(struct mtk_eth *eth, struct device_node *np)
>  
>  	mac->phylink = phylink;
>  
> +	if (name)
> +		strncpy(eth->netdev[id]->name, name, IFNAMSIZ);

Please don't use strncpy() - this is a good example why strncpy() is bad
news.

 * strncpy - Copy a length-limited, C-string
 * @dest: Where to copy the string to
 * @src: Where to copy the string from
 * @count: The maximum number of bytes to copy
 *
 * The result is not %NUL-terminated if the source exceeds
 * @count bytes.

Consequently, if "name" is IFNAMSIZ bytes or longer,
eth->netdev[id]->name will not be NUL terminated, and subsequent use
will run off the end of the string. strscpy() is safer to use here.

Thanks.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!