netdev - Re: [syzbot] [netfilter?] possible deadlock in nf_tables_dumpreset

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Message-ID: <aUkofscPurmzJ0Sh@strlen.de>
Date: Mon, 22 Dec 2025 12:16:14 +0100
From: Florian Westphal <fw@...len.de>
To: Pablo Neira Ayuso <pablo@...filter.org>
Cc: syzbot <syzbot+ff16b505ec9152e5f448@...kaller.appspotmail.com>,
	coreteam@...filter.org, davem@...emloft.net, edumazet@...gle.com,
	horms@...nel.org, kadlec@...filter.org, kuba@...nel.org,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	netfilter-devel@...r.kernel.org, pabeni@...hat.com, phil@....cc,
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [netfilter?] possible deadlock in
 nf_tables_dumpreset_obj

Pablo Neira Ayuso <pablo@...filter.org> wrote:
> > > CPU0: 'nft reset'.
> > > CPU1: 'ipset list' (anything in ipset doing a netlink dump op)
> > > CPU2: 'iptables-nft -A ... -m set ...'
> > > 
> > > ... can result in:
> > > 
> > > CPU0                    CPU1                            CPU2
> > > ----                    ----                            ----
> > > lock(nlk_cb_mutex-NETFILTER);
> > >                         lock(nfnl_subsys_ipset);
> > >                                                        lock(&nft_net->commit_mutex);
> > >                         lock(nlk_cb_mutex-NETFILTER);
> > >                                                        lock(nfnl_subsys_ipset);
> > > lock(&nft_net->commit_mutex);
> 
> Would it work to use a separated mutex for reset itself?

I think so, yes, its only job is to prevent concurrent reset actions,
the objects themselves are protected by rcu.

Parallel add/removal should be fine.