From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 58B74368D59; Fri, 10 Jul 2026 16:19:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783700397; cv=none; b=AdPrKe1/FnyGGiOIn0kmq0t7OgZ6/y/6XiQcZkJbzZUxGaWsFui7h0AmJCGIEKgumynDKFKfdaHGiwXdQfMcioFmxccyWk5YA/z7kNa4yyUCXf8N9DsDxnWArJny2hmBx21TGG/WgjzXWXs2SnKe/o1xFdPTGiNzsJmDj3DFR7Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783700397; c=relaxed/simple; bh=gwc1Zl5mINekUhb39fjvwrNJVc+2AXdQ8ZH/ukfVtFQ=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=avAJ0gwX9rybHuTpQWs98kJ8tTKuf5QmgwTtpE9+P4/ci7bh1uR6r8yty3Saqhs+YwbUl33mSDqNS4SpRVtn/k8RpRMG/R5upo7VFEdupP/ywQCTaQ91G9ZWZxM8LWDmPXr7m0eIzLlAW6Nppp4YpyNp/gdkof5m/VJ7LtcBHvQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=CMIuPEV+; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="CMIuPEV+" Received: by smtp.kernel.org (Postfix) with ESMTPSA id AA5331F000E9; Fri, 10 Jul 2026 16:19:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1783700394; bh=Nu3Wp1wI0A1+Gn22afTscrgbYWwQ7DDpD4i0bGHPoUM=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=CMIuPEV+ylHfmxqQaUJKod/WwjhVwUqlSKdgUj44kPWSTdEm+ue7I8k6mVjUa0czF uCaY1RPhxK4e0Vw+XU0jV0OKp5Dllq4qJp3k1LKYpx8+zQMD4znkevWtt3ygVJlb8b nmo6u8URlbTO4ox5smDZxL7k1fHZ+yh0gy38Xhl6+qSI//jdjmk4pzZRm3QkV16abB kK+O8fUVE7tqfA95s9jbCp1tT+Fa7zulqKkNgRLbVyQVUnKEX5P9wd9N7zUpV4Ss8u tlntoHD64jaTXxqLoKjqZ2aTKw0EzlvsVjrRG2+7TERLP0std6g3hjYLTJP5KzRAqy f+bWGrXDVylWQ== Message-ID: <5bb0177a-8d42-4301-8cf1-db4630f18437@kernel.org> Date: Fri, 10 Jul 2026 18:19:49 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Beta Subject: Re: [PATCH net v3] mptcp: only set DATA_FIN when a mapping is present Content-Language: fr To: Michael Bommarito , Mat Martineau Cc: Geliang Tang , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Gang Yan , mptcp@lists.linux.dev, netdev@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260709191925.2811195-1-michael.bommarito@gmail.com> From: Matthieu Baerts Autocrypt: addr=matttbe@kernel.org; keydata= xsFNBFXj+ekBEADxVr99p2guPcqHFeI/JcFxls6KibzyZD5TQTyfuYlzEp7C7A9swoK5iCvf YBNdx5Xl74NLSgx6y/1NiMQGuKeu+2BmtnkiGxBNanfXcnl4L4Lzz+iXBvvbtCbynnnqDDqU c7SPFMpMesgpcu1xFt0F6bcxE+0ojRtSCZ5HDElKlHJNYtD1uwY4UYVGWUGCF/+cY1YLmtfb WdNb/SFo+Mp0HItfBC12qtDIXYvbfNUGVnA5jXeWMEyYhSNktLnpDL2gBUCsdbkov5VjiOX7 CRTkX0UgNWRjyFZwThaZADEvAOo12M5uSBk7h07yJ97gqvBtcx45IsJwfUJE4hy8qZqsA62A nTRflBvp647IXAiCcwWsEgE5AXKwA3aL6dcpVR17JXJ6nwHHnslVi8WesiqzUI9sbO/hXeXw TDSB+YhErbNOxvHqCzZEnGAAFf6ges26fRVyuU119AzO40sjdLV0l6LE7GshddyazWZf0iac nEhX9NKxGnuhMu5SXmo2poIQttJuYAvTVUNwQVEx/0yY5xmiuyqvXa+XT7NKJkOZSiAPlNt6 VffjgOP62S7M9wDShUghN3F7CPOrrRsOHWO/l6I/qJdUMW+MHSFYPfYiFXoLUZyPvNVCYSgs 3oQaFhHapq1f345XBtfG3fOYp1K2wTXd4ThFraTLl8PHxCn4ywARAQABzSRNYXR0aGlldSBC YWVydHMgPG1hdHR0YmVAa2VybmVsLm9yZz7CwZEEEwEIADsCGwMFCwkIBwIGFQoJCAsCBBYC AwECHgECF4AWIQToy4X3aHcFem4n93r2t4JPQmmgcwUCZUDpDAIZAQAKCRD2t4JPQmmgcz33 EACjROM3nj9FGclR5AlyPUbAq/txEX7E0EFQCDtdLPrjBcLAoaYJIQUV8IDCcPjZMJy2ADp7 /zSwYba2rE2C9vRgjXZJNt21mySvKnnkPbNQGkNRl3TZAinO1Ddq3fp2c/GmYaW1NWFSfOmw MvB5CJaN0UK5l0/drnaA6Hxsu62V5UnpvxWgexqDuo0wfpEeP1PEqMNzyiVPvJ8bJxgM8qoC cpXLp1Rq/jq7pbUycY8GeYw2j+FVZJHlhL0w0Zm9CFHThHxRAm1tsIPc+oTorx7haXP+nN0J iqBXVAxLK2KxrHtMygim50xk2QpUotWYfZpRRv8dMygEPIB3f1Vi5JMwP4M47NZNdpqVkHrm jvcNuLfDgf/vqUvuXs2eA2/BkIHcOuAAbsvreX1WX1rTHmx5ud3OhsWQQRVL2rt+0p1DpROI 3Ob8F78W5rKr4HYvjX2Inpy3WahAm7FzUY184OyfPO/2zadKCqg8n01mWA9PXxs84bFEV2mP VzC5j6K8U3RNA6cb9bpE5bzXut6T2gxj6j+7TsgMQFhbyH/tZgpDjWvAiPZHb3sV29t8XaOF BwzqiI2AEkiWMySiHwCCMsIH9WUH7r7vpwROko89Tk+InpEbiphPjd7qAkyJ+tNIEWd1+MlX ZPtOaFLVHhLQ3PLFLkrU3+Yi3tXqpvLE3gO3LM7BTQRV4/npARAA5+u/Sx1n9anIqcgHpA7l 5SUCP1e/qF7n5DK8LiM10gYglgY0XHOBi0S7vHppH8hrtpizx+7t5DBdPJgVtR6SilyK0/mp 9nWHDhc9rwU3KmHYgFFsnX58eEmZxz2qsIY8juFor5r7kpcM5dRR9aB+HjlOOJJgyDxcJTwM 1ey4L/79P72wuXRhMibN14SX6TZzf+/XIOrM6TsULVJEIv1+NdczQbs6pBTpEK/G2apME7vf mjTsZU26Ezn+LDMX16lHTmIJi7Hlh7eifCGGM+g/AlDV6aWKFS+sBbwy+YoS0Zc3Yz8zrdbi Kzn3kbKd+99//mysSVsHaekQYyVvO0KD2KPKBs1S/ImrBb6XecqxGy/y/3HWHdngGEY2v2IP Qox7mAPznyKyXEfG+0rrVseZSEssKmY01IsgwwbmN9ZcqUKYNhjv67WMX7tNwiVbSrGLZoqf Xlgw4aAdnIMQyTW8nE6hH/Iwqay4S2str4HZtWwyWLitk7N+e+vxuK5qto4AxtB7VdimvKUs x6kQO5F3YWcC3vCXCgPwyV8133+fIR2L81R1L1q3swaEuh95vWj6iskxeNWSTyFAVKYYVskG V+OTtB71P1XCnb6AJCW9cKpC25+zxQqD2Zy0dK3u2RuKErajKBa/YWzuSaKAOkneFxG3LJIv Hl7iqPF+JDCjB5sAEQEAAcLBXwQYAQIACQUCVeP56QIbDAAKCRD2t4JPQmmgc5VnD/9YgbCr HR1FbMbm7td54UrYvZV/i7m3dIQNXK2e+Cbv5PXf19ce3XluaE+wA8D+vnIW5mbAAiojt3Mb 6p0WJS3QzbObzHNgAp3zy/L4lXwc6WW5vnpWAzqXFHP8D9PTpqvBALbXqL06smP47JqbyQxj Xf7D2rrPeIqbYmVY9da1KzMOVf3gReazYa89zZSdVkMojfWsbq05zwYU+SCWS3NiyF6QghbW voxbFwX1i/0xRwJiX9NNbRj1huVKQuS4W7rbWA87TrVQPXUAdkyd7FRYICNW+0gddysIwPoa KrLfx3Ba6Rpx0JznbrVOtXlihjl4KV8mtOPjYDY9u+8x412xXnlGl6AC4HLu2F3ECkamY4G6 UxejX+E6vW6Xe4n7H+rEX5UFgPRdYkS1TA/X3nMen9bouxNsvIJv7C6adZmMHqu/2azX7S7I vrxxySzOw9GxjoVTuzWMKWpDGP8n71IFeOot8JuPZtJ8omz+DZel+WCNZMVdVNLPOd5frqOv mpz0VhFAlNTjU1Vy0CnuxX3AM51J8dpdNyG0S8rADh6C8AKCDOfUstpq28/6oTaQv7QZdge0 JY6dglzGKnCi/zsmp2+1w559frz4+IC7j/igvJGX4KDDKUs0mlld8J2u2sBXv7CGxdzQoHaz lzVbFe7fduHbABmYz9cefQpO7wDE/Q== Organization: NGI0 Core In-Reply-To: <20260709191925.2811195-1-michael.bommarito@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Hi Michael, On 09/07/2026 21:19, Michael Bommarito wrote: > mptcp_get_options() clears only the status group of struct > mptcp_options_received; data_seq, subflow_seq and data_len are filled in > by mptcp_parse_option() exclusively inside the DSS mapping block, which > runs only when the DSS M (mapping present) bit is set. > > A peer can send a DSS option with the DATA_FIN flag set but the mapping > bit clear. The parser then records mp_opt->data_fin while leaving > data_len and data_seq uninitialized. For a zero-length segment > mptcp_incoming_options() evaluates > > if (mp_opt.data_fin && mp_opt.data_len == 1 && > mptcp_update_rcv_data_fin(msk, mp_opt.data_seq, mp_opt.dsn64)) > > which reads the uninitialized data_len and data_seq; KMSAN reports an > uninit-value in mptcp_incoming_options(). The stale data_seq can also be > fed into the receive-side DATA_FIN sequence tracking. > > Record the DATA_FIN flag only when the DSS option carries a mapping, so > data_fin is never set without data_seq and data_len also being present. > data_fin is part of the status group that mptcp_get_options() clears up > front, so on the no-map path it stays zero and the zero-length DATA_FIN > branch is simply skipped. A DATA_FIN is always transmitted together with > a mapping (mptcp_write_data_fin() sets use_map along with data_seq and > data_len), so legitimate DATA_FIN handling is unaffected. > > Move the pr_debug() that logs the parsed DSS flags below the mapping > block, so it reports the final data_fin value instead of the stale one > it would otherwise print before the assignment. Thank you for the v3, it looks good to me: Reviewed-by: Matthieu Baerts (NGI0) I tried to reproduce it on my side using packetdrill-mptcp [1], but I was not able to test with KMSAN: my kernel boot, but is stuck when KMSAN is enabled... By chance, if you can try this reproducer on your side, with and without your patched kernel, that would be great :) [1] https://github.com/multipath-tcp/packetdrill/pull/203 Cheers, Matt -- Sponsored by the NGI0 Core fund.