linux-kernel - Re: [PATCH 1/1] netfilter: nf_tables: fib: Drop IPV6 packages if IPv6 is disabled on boot

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Message-ID: <20190820053607.GL2588@breakpoint.cc>
Date:   Tue, 20 Aug 2019 07:36:07 +0200
From:   Florian Westphal <fw@...len.de>
To:     Leonardo Bras <leonardo@...ux.ibm.com>
Cc:     netfilter-devel@...r.kernel.org, coreteam@...filter.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>,
        "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH 1/1] netfilter: nf_tables: fib: Drop IPV6 packages if
 IPv6 is disabled on boot

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 package, 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
> 
> Fix this behavior by dropping IPv6 packages if !ipv6_mod_enabled().

Wouldn't fib_netdev.c have the same problem?

If so, might be better to place this test in both
nft_fib6_eval_type and nft_fib6_eval.