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Date: Sat, 13 Dec 2025 14:40:20 +0100
From: Florian Westphal <fw@strlen.de>
To: Eric Dumazet <edumazet@google.com>
Cc: Jakub Kicinski <kuba@kernel.org>,
	syzbot <syzbot+4393c47753b7808dac7d@syzkaller.appspotmail.com>,
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Subject: Re: [syzbot] [netfilter?] WARNING in nf_conntrack_cleanup_net_list
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 <20251213080716.27a25928@kernel.org>
 <aT1pyVp3pQRvCjLn@strlen.de>
 <CANn89i+V0XfUMjo5azSAkcr6EKucQFs6fv6mpNeL3rN41SsTzg@mail.gmail.com>
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Eric Dumazet <edumazet@google.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).