Re: [PATCH net 1/3] bpf: bpf_out_neigh_v4: Fix nd_tbl NULL dereference when IPv6 is disabled

[Daniel Borkmann]

On 3/5/26 2:43 AM, Jakub Kicinski wrote:
> On Thu, 5 Mar 2026 02:34:00 +0100 Daniel Borkmann wrote:
> > > Maybe I am missing something here, but I believe this won't solve
> > > the problem. Even if ipv6 is built-in, it should be possible to
> > > pass ipv6.disable=1 during boot and therefore nd_tbl would still be
> > > uninitialized, not NULL tho.
> >
> > I presume you mean disable_ipv6_mod which then bails out during the module
> > load process without error, right? It could be deprecated with a warning so
> > that it turns into a no-op:
>
> I believe disabling ipv6 may be legit. Some admins on ipv4 networks may
> be paranoid and not want to allow any ipv6 traffic if their "firewalls"
> can only understand IPv6? This is just a guess on my side, but I'm less
> confident of deprecating the disable knob than =m. I'd be happy if I'm
> wrong.
>
> To answer the earlier question -- I would prefer to take the fixes now
> and make IPv6 bool in net-next, feels like too big of a change for rc3
> :(

Makes sense, I think starting this process via net-next is fine and can be
better justified. Fernando, maybe in that case resend with the unlikely()
added.

Thanks,
Daniel