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

Pablo Neira Ayuso
2019-09-03T16:49:55Z

On Tue, Sep 03, 2019 at 01:46:50PM -0300, Leonardo Bras wrote:
> On Fri, 2019-08-30 at 22:58 +0200, Florian Westphal wrote:
> > Leonardo Bras <leonardo@linux.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@linux.ibm.com>
> >
> > Acked-by: Florian Westphal <fw@strlen.de>
> >
>
> Hello Pablo,
>
> Any trouble with this patch?
> I could see the other* one got applied, but not this one.
> *(The other did not get acked, so i released it alone as v5)
>
> Is there any fix I need to do in this one?

Hm, I see, so this one:

https://patchwork.ozlabs.org/patch/1156100/

is not enough?

I was expecting we could find a way to handle this from br_netfilter
alone itself.

Thanks.