netdev - Re: [PATCH net 1/2] net: dsa: realtek: fix out-of-bounds access

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Message-ID: <20230315132134.3xzj7nemljhgtqbg@bang-olufsen.dk>
Date:   Wed, 15 Mar 2023 13:21:35 +0000
From:   Alvin Šipraga <ALSI@...g-olufsen.dk>
To:     Ahmad Fatoum <a.fatoum@...gutronix.de>
CC:     Linus Walleij <linus.walleij@...aro.org>,
        Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        Luiz Angelo Daros de Luca <luizluca@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net 1/2] net: dsa: realtek: fix out-of-bounds access

On Wed, Mar 15, 2023 at 02:09:15PM +0100, Ahmad Fatoum wrote:
> The probe function sets priv->chip_data to (void *)priv + sizeof(*priv)
> with the expectation that priv has enough trailing space.
> 
> However, only realtek-smi actually allocated this chip_data space.
> Do likewise in realtek-mdio to fix out-of-bounds accesses.
> 
> Fixes: aac94001067d ("net: dsa: realtek: add new mdio interface for drivers")
> Signed-off-by: Ahmad Fatoum <a.fatoum@...gutronix.de>
> ---

Reviewed-by: Alvin Šipraga <alsi@...g-olufsen.dk>

Makes me wonder how the switches worked over MDIO all this time... I
guess it was dumb luck.

>  drivers/net/dsa/realtek/realtek-mdio.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/dsa/realtek/realtek-mdio.c b/drivers/net/dsa/realtek/realtek-mdio.c
> index 3e54fac5f902..3b22d3f7ad99 100644
> --- a/drivers/net/dsa/realtek/realtek-mdio.c
> +++ b/drivers/net/dsa/realtek/realtek-mdio.c
> @@ -152,7 +152,7 @@ static int realtek_mdio_probe(struct mdio_device *mdiodev)
>  	if (!var)
>  		return -EINVAL;
>  
> -	priv = devm_kzalloc(&mdiodev->dev, sizeof(*priv), GFP_KERNEL);
> +	priv = devm_kzalloc(&mdiodev->dev, sizeof(*priv) + var->chip_data_sz, GFP_KERNEL);
>  	if (!priv)
>  		return -ENOMEM;
>  
> -- 
> 2.30.2
>