From: Pablo Neira Ayuso <pablo@netfilter.org>
To: Florian Westphal <fw@strlen.de>
Cc: netfilter-devel@vger.kernel.org
Subject: Re: [PATCH nf] netfilter: nf_tables: avoid skb access on nf_stolen
Date: Tue, 28 Jun 2022 19:01:49 +0200 [thread overview]
Message-ID: <Yrsz88r5osn6nirQ@salvia> (raw)
In-Reply-To: <20220622144357.20162-1-fw@strlen.de>
On Wed, Jun 22, 2022 at 04:43:57PM +0200, Florian Westphal wrote:
> When verdict is NF_STOLEN, the skb might have been freed.
>
> When tracing is enabled, this can result in a use-after-free:
> 1. access to skb->nf_trace
> 2. access to skb->mark
> 3. computation of trace id
> 4. dump of packet payload
>
> To avoid 1, keep a cached copy of skb->nf_trace in the
> trace state struct.
> Refresh this copy whenever verdict is != STOLEN.
>
> Avoid 2 by skipping skb->mark access if verdict is STOLEN.
>
> 3 is avoided by precomputing the trace id.
>
> Only dump the packet when verdict is not "STOLEN".
Applied, thanks
prev parent reply other threads:[~2022-06-28 17:02 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-22 14:43 [PATCH nf] netfilter: nf_tables: avoid skb access on nf_stolen Florian Westphal
2022-06-28 17:01 ` Pablo Neira Ayuso [this message]
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