netdev - Re: [PATCH v4 1/2] netfilter: Terminate rule eval if protocol=IPv6 and ipv6 module is disabled

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Date:   Fri, 30 Aug 2019 22:58:02 +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 v4 1/2] netfilter: Terminate rule eval if protocol=IPv6
 and ipv6 module is disabled

Leonardo Bras <leonardo@...ux.ibm.com> wrote:
> If IPv6 is disabled on boot (ipv6.disable=1), but nft_fib_inet ends up
> dealing with a IPv6 packet, it causes a kernel panic in
> fib6_node_lookup_1(), crashing in bad_page_fault.
> 
> The panic is caused by trying to deference a very low address (0x38
> in ppc64le), due to ipv6.fib6_main_tbl = NULL.
> BUG: Kernel NULL pointer dereference at 0x00000038
> 
> The kernel panic was reproduced in a host that disabled IPv6 on boot and
> have to process guest packets (coming from a bridge) using it's ip6tables.
> 
> Terminate rule evaluation when packet protocol is IPv6 but the ipv6 module
> is not loaded.
> 
> Signed-off-by: Leonardo Bras <leonardo@...ux.ibm.com>

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