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[78.154.15.182]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-c250a5d62dfsm738498266b.4.2026.08.27.07.35.51 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 27 Aug 2026 07:35:51 -0700 (PDT) Message-ID: Date: Thu, 27 Aug 2026 17:35:50 +0300 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [BUG] net/bridge: out-of-bounds in br_forward() Content-Language: en-US, bg To: Florian Westphal , netfilter-devel@vger.kernel.org Cc: bridge@lists.linux.dev, netdev@vger.kernel.org, Pablo Neira Ayuso , Ido Schimmel , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Sabrina Dubroca , Phil Sutter , Simon Horman , linux-kernel@vger.kernel.org References: From: Nikolay Aleksandrov In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 27/08/2026 17:29, Florian Westphal wrote: > co wrote: >> We found a bug reachable in: >> >> path net/bridge/netfilter >> crash out-of-bounds in br_forward() >> commit 7b5344954050 ("Merge tag 'nf-26-08-10' of git://git.kernel.org/pub/scm/linux/kernel/git/netfilter/nf") > > I'm looking into these reports, I think this is the same > underlying bug as the other report; a variant of > > ccb9fd4b8753 ("netfilter: revalidate bridge ports") > > That bug uses nfnetlink_queue for RCU escape, the other two reports > use defrag engine. > > And sure, its br_netfilter again -- I think we will have to consider > removing it even though it will break existing setups. > +10 > As a compromise, I suggest to reject br_netfilter in user namespaces, > i.e. call_iptables cannot be enabled anymore unless you have > CAP_NET_ADMIN in init net. +1000 :) I absolutely agree on both counts.