Subject: Re: [syzbot] [netfilter?] WARNING in nf_conntrack_cleanup_net_list

From: Jakub Kicinski <[email-masked]>
Date: Sat, 13 Dec 2025 08:07:16 +0900

On Thu, 11 Dec 2025 10:38:31 -0800 syzbot wrote:
> ------------[ cut here ]------------
> conntrack cleanup blocked for 60s
> WARNING: net/netfilter/nf_conntrack_core.c:2512 at

Yes, I was about to comment on the patch which added the warning..

There is still a leak somewhere. Running ip_defrag.sh and then load /
unload ipvlan repros this (modprobe ipvlan is a quick check if the
cleanup thread is wedged, if it is modprobe will hang, if it isn't
run ip_defrag.sh, again etc).

I looked around last night but couldn't find an skb stuck anywhere.
The nf_conntrack_net->count was == 1