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From: Pablo Neira Ayuso <pablo@netfilter.org>
To: David Lee <david.lee@trailofbits.com>
Cc: fw@strlen.de, davem@davemloft.net, edumazet@google.com,
	kuba@kernel.org, pabeni@redhat.com,
	Kyle Zeng <kylebot@openai.com>,
	Dominik 'Disconnect3d' Czarnota
	<dominik.czarnota@trailofbits.com>,
	phil@nwl.cc, horms@kernel.org, netfilter-devel@vger.kernel.org,
	coreteam@netfilter.org, netdev@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] netfilter: nf_conntrack: prevent helper extension relocation
Date: Fri, 31 Jul 2026 17:37:07 +0200	[thread overview]
Message-ID: <amzBI6YKhMX3Ezib@chamomile> (raw)
In-Reply-To: <20260731140811.566714-1-david.lee@trailofbits.com>

On Fri, Jul 31, 2026 at 02:08:10PM +0000, David Lee wrote:
> struct nf_conn_help contains the head of the per-master expectation
> list. hlist_add_head_rcu() makes the first expectation node point back to
> that head, but nf_ct_ext_add() can later move the extension buffer with
> krealloc(). This leaves the node backpointer aimed at freed memory, so
> unlinking the expectation writes through a stale pointer.
> 
> Reserve the full u8-addressable extension space when adding the helper
> extension and reuse the existing buffer once the helper is present. This
> keeps the expectation list head stable while allowing later extensions
> to be added.
> 
> Fixes: 857b46027d6f ("netfilter: nft_ct: add ct expectations support")
> Bug found and triaged by OpenAI Security Research and 
> validated by Trail of Bits.

Thanks for your patch.

This is a duplicate of:

https://patchwork.ozlabs.org/project/netfilter-devel/patch/20260715144755.00ea7dfcd9f@proton.me/

proposed fix tackles the problem from the ct expectation feature angle:

https://patchwork.ozlabs.org/project/netfilter-devel/patch/20260730150305.617144-1-pablo@netfilter.org/

      reply	other threads:[~2026-07-31 15:37 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-07-31 14:08 David Lee
2026-07-31 15:37 ` Pablo Neira Ayuso [this message]

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