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

From: Florian Westphal <[email-masked]>
Date: Sat, 13 Dec 2025 14:40:20 +0100

Eric Dumazet <[email-masked]> wrote:
> > > I looked around last night but couldn't find an skb stuck anywhere.
> > > The nf_conntrack_net->count was == 1
> >
> > Its caused skb skb fraglist skbs that still hold nf_conn references
> > on the softnet data defer lists.
> >
> > setting net.core.skb_defer_max=0 makes the hang disappear for me.
> 
> What kind of packets ? TCP ones ?

UDP, but I can't say yet if thats an udp specific issue or not.
(the packets are generated via ip_defrag.c).