Subject: Re: [PATCH v1] i40e: Add length check for IFLA_AF_SPEC parsing

From: Leon Romanovsky <[email-masked]>
Date: Mon, 24 Jul 2023 20:44:35 +0300

On Sun, Jul 23, 2023 at 03:50:42PM +0800, Lin Ma wrote:
> The nla_for_each_nested parsing in function i40e_ndo_bridge_setlink()
> does not check the length of the attribute. This can lead to an
> out-of-attribute read and allow a malformed nlattr (e.g., length 0) to
> be viewed as a 2 byte integer.
> 
> This patch adds the check based on nla_len() just as other code does,
> see how bnxt_bridge_setlink (drivers/net/ethernet/broadcom/bnxt/bnxt.c)
> parses IFLA_AF_SPEC: type checking plus length checking.
> 
> Fixes: 51616018dd1b ("i40e: Add support for getlink, setlink ndo ops")
> Signed-off-by: Lin Ma <[email-masked]>
> ---
>  drivers/net/ethernet/intel/i40e/i40e_main.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/net/ethernet/intel/i40e/i40e_main.c b/drivers/net/ethernet/intel/i40e/i40e_main.c
> index 29ad1797adce..6363357bdeeb 100644
> --- a/drivers/net/ethernet/intel/i40e/i40e_main.c
> +++ b/drivers/net/ethernet/intel/i40e/i40e_main.c
> @@ -13186,6 +13186,9 @@ static int i40e_ndo_bridge_setlink(struct net_device *dev,
>  		if (nla_type(attr) != IFLA_BRIDGE_MODE)
>  			continue;
>  
> +		if (nla_len(attr) < sizeof(mode))
> +			return -EINVAL;
> +

I see that you added this hunk to all users of nla_for_each_nested(), it
will be great to make that iterator to skip such empty attributes.

However, i don't know nettlink good enough to say if your change is
valid in first place.

Thanks

>  		mode = nla_get_u16(attr);
>  		if ((mode != BRIDGE_MODE_VEPA) &&
>  		    (mode != BRIDGE_MODE_VEB))
> -- 
> 2.17.1
> 
>