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Tue, 09 Jul 2024 03:40:25 -0700 (PDT) X-Google-Smtp-Source: AGHT+IHNCKJ0T7kZ55W4np4jEaOXrU3VVZKHqlYR3BXWtqZzKQ7qSmz5O3yTc2H9GGMw6jEQR7/Y5Q== X-Received: by 2002:a05:6000:2ad:b0:367:4d9d:56a6 with SMTP id ffacd0b85a97d-367cea452damr1529322f8f.1.1720521624681; Tue, 09 Jul 2024 03:40:24 -0700 (PDT) Received: from gerbillo.redhat.com ([2a0d:3344:1710:e810:1180:8096:5705:abe]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-367cdfab09esm2161820f8f.101.2024.07.09.03.40.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 09 Jul 2024 03:40:24 -0700 (PDT) Message-ID: <16e61611ecc9209bdf7de68f77804793386850dd.camel@redhat.com> Subject: Re: [PATCH net v2] net/sched: Fix UAF when resolving a clash From: Paolo Abeni To: Chengen Du , Michal Kubiak Cc: Florian Westphal , jhs@mojatatu.com, xiyou.wangcong@gmail.com, jiri@resnulli.us, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, ozsh@nvidia.com, paulb@nvidia.com, marcelo.leitner@gmail.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Gerald Yang Date: Tue, 09 Jul 2024 12:40:22 +0200 In-Reply-To: References: <20240705025056.12712-1-chengen.du@canonical.com> <20240705093525.GA30758@breakpoint.cc> Autocrypt: addr=pabeni@redhat.com; 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charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.50.4 (3.50.4-1.fc39) Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Mon, 2024-07-08 at 17:39 +0800, Chengen Du wrote: > On Mon, Jul 8, 2024 at 4:33=E2=80=AFPM Michal Kubiak wrote: > > For example, if "nf_conntrack_confirm()" returns NF_ACCEPT, (even after > > the clash resolving), I would not expect calling "goto drop". > > That is why I suggested a less invasive solution which is just blocking > > calling "tcf_ct_flow_table_process_conn()" where there is a risk of UAF= . > > So, I asked if such solution would work in case of this function. >=20 > Thank you for expressing your concerns in detail. >=20 > In my humble opinion, skipping the addition of an entry in the flow > table is controlled by other logic and may not be suitable to mix with > error handling. If nf_conntrack_confirm returns NF_ACCEPT, I believe > there is no reason for nf_ct_get to fail. The nf_ct_get function > simply converts skb->_nfct into a struct nf_conn type. The only > instance it might fail is when CONFIG_NF_CONNTRACK is disabled. The > CONFIG_NET_ACT_CT depends on this configuration and determines whether > act_ct.c needs to be compiled. Actually, the "goto drop" logic is > included for completeness and might only be relevant if the memory is > corrupted. Perhaps we could wrap the judgment with "unlikely" to > emphasize this point? I agree with Michal, I think it should be better to just skip tcf_ct_flow_table_process_conn() in case of clash to avoid potential behavior changes. Thanks, Paolo