linux-kernel - Re: [PATCH v5 1/1] net: br_netfiler_hooks: Drops IPv6 packets if IPv6 module is not loaded

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Message-ID: <20190831083859.GT20113@breakpoint.cc>
Date:   Sat, 31 Aug 2019 10:38:59 +0200
From:   Florian Westphal <fw@...len.de>
To:     Leonardo Bras <leonardo@...ux.ibm.com>
Cc:     netfilter-devel@...r.kernel.org, coreteam@...filter.org,
        bridge@...ts.linux-foundation.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Pablo Neira Ayuso <pablo@...filter.org>,
        Jozsef Kadlecsik <kadlec@...filter.org>,
        Florian Westphal <fw@...len.de>,
        Roopa Prabhu <roopa@...ulusnetworks.com>,
        Nikolay Aleksandrov <nikolay@...ulusnetworks.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH v5 1/1] net: br_netfiler_hooks: Drops IPv6 packets if
 IPv6 module is not loaded

Leonardo Bras <leonardo@...ux.ibm.com> wrote:
> A kernel panic can happen if a host has disabled IPv6 on boot and have to
> process guest packets (coming from a bridge) using it's ip6tables.
> 
> IPv6 packets need to be dropped if the IPv6 module is not loaded, and the
> host ip6tables will be used.
> 
> Signed-off-by: Leonardo Bras <leonardo@...ux.ibm.com>
> ---
> Changes from v4:
> - Check if the host ip6tables is going to be used before testing 
>   ipv6 module presence 
> - Adds a warning about ipv6 module disabled.
> 
> 
>  net/bridge/br_netfilter_hooks.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/net/bridge/br_netfilter_hooks.c b/net/bridge/br_netfilter_hooks.c
> index d3f9592f4ff8..af7800103e51 100644
> --- a/net/bridge/br_netfilter_hooks.c
> +++ b/net/bridge/br_netfilter_hooks.c
> @@ -496,6 +496,10 @@ static unsigned int br_nf_pre_routing(void *priv,
>  		if (!brnet->call_ip6tables &&
>  		    !br_opt_get(br, BROPT_NF_CALL_IP6TABLES))
>  			return NF_ACCEPT;
> +		if (!ipv6_mod_enabled()) {
> +			pr_warn_once("Module ipv6 is disabled, so call_ip6tables is not supported.");
> +			return NF_DROP;
> +		}

pr_warn_once needs a '\n'.  Pablo, can you mangle this locally when
applying?

Patch looks good to me, so:

Acked-by: Florian Westphal <fw@...len.de>