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Date: Wed, 7 Oct 2026 13:26:27 +0200
From: Florian Westphal <fw@strlen.de>
To: Pablo Neira Ayuso <pablo@netfilter.org>
Cc: Daehyeon Ko <4ncienth@gmail.com>, phil@nwl.cc,
	netfilter-devel@vger.kernel.org, coreteam@netfilter.org,
	netdev@vger.kernel.org, stable@vger.kernel.org
Subject: Re: [PATCH net v3] netfilter: conntrack: avoid recursive master
 destruction
Message-ID: <asYsY-yLXNVFc_Rv@strlen.de>
References: <20261007014802.2615503-1-4ncienth@gmail.com>
 <asYHaUFdxo0flpAe@strlen.de>
 <asYf2b03D78kWdkZ@chamomile>
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In-Reply-To: <asYf2b03D78kWdkZ@chamomile>

Pablo Neira Ayuso <pablo@netfilter.org> wrote:
> > That said, ignoring the source of the problem is not good.
> > 
> > I see no point whatsoever for a expected connection to have a
> > non-control connection as its master.
> 
> I would prefer if chain length is limited too, ie. tighten this
> interface based on the LLM feedback.

Thanks, working on this now.  Tentative plan:

#define NF_CT_MAX_EXPECT_CHAIN_LEN     4

static inline bool nf_ct_master_acceptable(const struct nf_conn *m)
{
       unsigned int depth = 0;

       while (m->master) {
               if (++depth > NF_CT_MAX_EXPECT_CHAIN_LEN)
                       return false;
               m = m->master;
       }

       return true;
}

 struct nf_conntrack_expect *nf_ct_expect_alloc(struct nf_conn *me)
 {
        struct nf_conntrack_expect *new;
 
+       if (!nf_ct_master_acceptable(me))
+               return NULL;
+

I'll make an independent submission for this.