Subject: Re: [PATCH] i40e: Add checking for null for nlmsg_find_attr()

From: Simon Horman <[email-masked]>
Date: Wed, 25 Jan 2023 16:08:12 +0100

On Wed, Jan 25, 2023 at 05:13:28PM +0300, Natalia Petrova wrote:
> The result of nlmsg_find_attr() 'br_spec' is dereferenced in
> nla_for_each_nested, but it can take null value in 'nla_find' finction,
> which will result in an error.
> 
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
> 
> Fixes: 51616018dd1b ("i40e: Add support for getlink, setlink ndo ops")
> Signed-off-by: Natalia Petrova <[email-masked]>
> ---
>  drivers/net/ethernet/intel/i40e/i40e_main.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/net/ethernet/intel/i40e/i40e_main.c b/drivers/net/ethernet/intel/i40e/i40e_main.c
> index b36bf9c3e1e4..ed4be4ffeb09 100644
> --- a/drivers/net/ethernet/intel/i40e/i40e_main.c
> +++ b/drivers/net/ethernet/intel/i40e/i40e_main.c
> @@ -13101,6 +13101,8 @@ static int i40e_ndo_bridge_setlink(struct net_device *dev,
>  	}
>  
>  	br_spec = nlmsg_find_attr(nlh, sizeof(struct ifinfomsg), IFLA_AF_SPEC);
> +	if (!br_spec)
> +		return -ENOENT;

Seems fine to me, but I wonder if -EINVAL is more appropriate.
nlh is invalid in this case.

>  
>  	nla_for_each_nested(attr, br_spec, rem) {
>  		__u16 mode;
> -- 
> 2.34.1
>