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([2a0d:3344:5521:6b10:2eb7:f61a:75:4534]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4926c278ab2sm182095195e9.1.2026.06.29.06.14.56 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 29 Jun 2026 06:14:57 -0700 (PDT) Message-ID: <2edcb1cd-f2db-4d0c-a0e3-fd2b4dd820fe@redhat.com> Date: Mon, 29 Jun 2026 15:14:55 +0200 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mptcp: only honor zero-length DATA_FIN when a mapping is present To: Michael Bommarito Cc: Matthieu Baerts , Mat Martineau , Geliang Tang , Eric Dumazet , Jakub Kicinski , mptcp@lists.linux.dev, netdev@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260617215725.1116295-1-michael.bommarito@gmail.com> <3ad5bba8-18b9-48a6-94e0-99d958f23984@redhat.com> From: Paolo Abeni Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 6/29/26 1:00 PM, Michael Bommarito wrote: > On Mon, Jun 29, 2026 at 5:50 AM Paolo Abeni wrote: >> Isn't this fixed by commit 5e939544f9d2 ("mptcp: fix uninit-value in >> mptcp_established_options") ? > > I did the reproduction ~10 days ago on linus's latest, so definitely > still reproducing. I think 5e939544f9d2 was on the TX side and this > is about the RX option path, so they don't overlap on flows either. Right. AFAICS the RFC is a little vague about enforcing meaningful flags combination. I think it would be better to avoid another conditional while processing incoming ack. Does the following solve the issue? Thanks! --- diff --git a/net/mptcp/options.c b/net/mptcp/options.c index 0ca60314d667..b924209a9b74 100644 --- a/net/mptcp/options.c +++ b/net/mptcp/options.c @@ -157,7 +157,6 @@ static void mptcp_parse_option(const struct sk_buff *skb, ptr++; flags = (*ptr++) & MPTCP_DSS_FLAG_MASK; - mp_opt->data_fin = (flags & MPTCP_DSS_DATA_FIN) != 0; mp_opt->dsn64 = (flags & MPTCP_DSS_DSN64) != 0; mp_opt->use_map = (flags & MPTCP_DSS_HAS_MAP) != 0; mp_opt->ack64 = (flags & MPTCP_DSS_ACK64) != 0; @@ -178,6 +177,7 @@ static void mptcp_parse_option(const struct sk_buff *skb, } if (mp_opt->use_map) { + mp_opt->data_fin = (flags & MPTCP_DSS_DATA_FIN) != 0; if (mp_opt->dsn64) expected_opsize += TCPOLEN_MPTCP_DSS_MAP64; else