netdev - Re: [PATCH nf-next 2/6] netfilter: bridge: check len before accessing more nh data

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Date:   Mon, 6 Mar 2023 16:59:37 +0100
From:   Simon Horman <simon.horman@...igine.com>
To:     Xin Long <lucien.xin@...il.com>
Cc:     netfilter-devel@...r.kernel.org,
        network dev <netdev@...r.kernel.org>,
        Pablo Neira Ayuso <pablo@...filter.org>,
        Jozsef Kadlecsik <kadlec@...filter.org>,
        Florian Westphal <fw@...len.de>, davem@...emloft.net,
        kuba@...nel.org, Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Roopa Prabhu <roopa@...dia.com>,
        Nikolay Aleksandrov <razor@...ckwall.org>,
        Pravin B Shelar <pshelar@....org>,
        Aaron Conole <aconole@...hat.com>
Subject: Re: [PATCH nf-next 2/6] netfilter: bridge: check len before
 accessing more nh data

On Fri, Mar 03, 2023 at 07:12:38PM -0500, Xin Long wrote:
> In the while loop of br_nf_check_hbh_len(), similar to ip6_parse_tlv(),
> before accessing 'nh[off + 1]', it should add a check 'len < 2'; and
> before parsing IPV6_TLV_JUMBO, it should add a check 'optlen > len',
> in case of overflows.
> 
> Signed-off-by: Xin Long <lucien.xin@...il.com>

Reviewed-by: Simon Horman <simon.horman@...igine.com>

> ---
>  net/bridge/br_netfilter_ipv6.c | 47 ++++++++++++++++------------------
>  1 file changed, 22 insertions(+), 25 deletions(-)
> 
> diff --git a/net/bridge/br_netfilter_ipv6.c b/net/bridge/br_netfilter_ipv6.c
> index 5cd3e4c35123..50f564c33551 100644
> --- a/net/bridge/br_netfilter_ipv6.c
> +++ b/net/bridge/br_netfilter_ipv6.c

...

> -	if (len == 0)
> -		return 0;
> -bad:
> -	return -1;
> +	if (len)
> +		return -1;
> +
> +	return 0;

nit: if you have to spin a v2, you may want to consider

	return len ? -1 : 0;