Subject: Re: [PATCH net-next] ipv6: blackhole_netdev needs snmp6 counters

From: Ido Schimmel <[email-masked]>
Date: Mon, 14 Feb 2022 09:44:02 +0200

On Sun, Feb 13, 2022 at 06:10:56PM -0800, Eric Dumazet wrote:
> From: Ido Schimmel <[email-masked]>
> 
> Whenever rt6_uncached_list_flush_dev() swaps rt->rt6_idev
> to the blackhole device, parts of IPv6 stack might still need
> to increment one SNMP counter.
> 
> Root cause, patch from Ido, changelog from Eric :)
> 
> This bug suggests that we need to audit rt->rt6_idev usages
> and make sure they are properly using RCU protection.
> 
> Fixes: e5f80fcf869a ("ipv6: give an IPv6 dev to blackhole_netdev")
> Signed-off-by: Ido Schimmel <[email-masked]>
> Signed-off-by: Eric Dumazet <[email-masked]>
> Reported-by: syzbot <[email-masked]>

Thanks for taking care of this, Eric. I applied the patch to our tree
last night before logging off and regression does look fine.