linux-kernel - Re: Soft lock-ups caused by iptables

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Message-ID: <aR4Ildw_PYHPAkPo@orbyte.nwl.cc>
Date: Wed, 19 Nov 2025 19:12:37 +0100
From: Phil Sutter <phil@....cc>
To: Florian Westphal <fw@...len.de>
Cc: Hamza Mahfooz <hamzamahfooz@...ux.microsoft.com>,
	netdev@...r.kernel.org, Pablo Neira Ayuso <pablo@...filter.org>,
	Jozsef Kadlecsik <kadlec@...filter.org>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Simon Horman <horms@...nel.org>, netfilter-devel@...r.kernel.org,
	coreteam@...filter.org, linux-kernel@...r.kernel.org
Subject: Re: Soft lock-ups caused by iptables

On Wed, Nov 19, 2025 at 04:58:46PM +0100, Florian Westphal wrote:
> Phil Sutter <phil@....cc> wrote:
> > On nftables side, maybe we could annotate chains with a depth value once
> > validated to skip digging into them again when revisiting from another
> > jump?
> 
> Yes, but you also need to annotate the type of the last base chain origin,
> else you might skip validation of 'chain foo' because its depth value says its
> fine but new caller is coming from filter, not nat, and chain foo had
> masquerade expression.

There would need to be masks of valid types and hooks recording the
restrictions imposed on a non-base chain by its rules' expressions.
Maybe this even needs a matrix for cases where some hooks are OK in some
families/types but not others.

Cheers, Phil