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Date: Wed, 24 Jun 2026 22:19:23 +0200
From: Florian Westphal <fw@strlen.de>
To: Theodor Arsenij Larionov-Trichkine <theodorlarionov@gmail.com>
Cc: Pablo Neira Ayuso <pablo@netfilter.org>, Phil Sutter <phil@nwl.cc>,
	netfilter-devel@vger.kernel.org, coreteam@netfilter.org
Subject: Re: [BUG] netfilter: nft_fib: NULL-ptr-deref (GPF) in nft_fib6_eval
 on netdev egress hook
Message-ID: <ajw7y1y7E8yyasOy@strlen.de>
References: <CAEZyMPC0BQ=FO80mi3BVZaL4=T9y6=MYVL32St=Ck4w53hASqg@mail.gmail.com>
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In-Reply-To: <CAEZyMPC0BQ=FO80mi3BVZaL4=T9y6=MYVL32St=Ck4w53hASqg@mail.gmail.com>

Theodor Arsenij Larionov-Trichkine <theodorlarionov@gmail.com> wrote:
> A `fib' expression in a netdev `egress' base chain dereferences the input
> device nft_in(pkt), which is NULL on the transmit path, so any IPv6 packet
> leaving the chain's device hits a GPF / KASAN NULL-ptr-deref. An unprivileged
> user can set this up in a user+net namespace.

Please just send a patch to disable fib on egress.