linux-kernel - Re: [syzbot] [netfilter?] WARNING in nf_conntrack_cleanup_net

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Message-ID: <aT1sxJHiK1mcrXaE@strlen.de>
Date: Sat, 13 Dec 2025 14:40:20 +0100
From: Florian Westphal <fw@...len.de>
To: Eric Dumazet <edumazet@...gle.com>
Cc: Jakub Kicinski <kuba@...nel.org>,
	syzbot <syzbot+4393c47753b7808dac7d@...kaller.appspotmail.com>,
	coreteam@...filter.org, davem@...emloft.net, horms@...nel.org,
	kadlec@...filter.org, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org, netfilter-devel@...r.kernel.org,
	pabeni@...hat.com, pablo@...filter.org, phil@....cc,
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [netfilter?] WARNING in nf_conntrack_cleanup_net_list

Eric Dumazet <edumazet@...gle.com> 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).