From: Florian Westphal <fw@strlen.de>
To: Jakub Kicinski <kuba@kernel.org>
Cc: syzbot <syzbot+4393c47753b7808dac7d@syzkaller.appspotmail.com>,
coreteam@netfilter.org, davem@davemloft.net, edumazet@google.com,
horms@kernel.org, kadlec@netfilter.org,
linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
netfilter-devel@vger.kernel.org, pabeni@redhat.com,
pablo@netfilter.org, phil@nwl.cc,
syzkaller-bugs@googlegroups.com
Subject: Re: [syzbot] [netfilter?] WARNING in nf_conntrack_cleanup_net_list
Date: Sat, 13 Dec 2025 14:27:37 +0100 [thread overview]
Message-ID: <aT1pyVp3pQRvCjLn@strlen.de> (raw)
In-Reply-To: <20251213080716.27a25928@kernel.org>
Jakub Kicinski <kuba@kernel.org> wrote:
> 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
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.
next prev parent reply other threads:[~2025-12-13 13:27 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-12-11 18:38 [syzbot] [netfilter?] WARNING in nf_conntrack_cleanup_net_list syzbot
2025-12-12 23:07 ` Jakub Kicinski
2025-12-13 13:27 ` Florian Westphal [this message]
2025-12-13 13:30 ` Eric Dumazet
2025-12-13 13:40 ` Florian Westphal
2025-12-13 13:58 ` Eric Dumazet
2025-12-13 18:54 ` Florian Westphal
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