From nobody Sat Jul 25 07:27:28 2026 Received: from mail-qk1-f169.google.com (mail-qk1-f169.google.com [209.85.222.169]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4318843786F for ; Tue, 7 Jul 2026 17:17:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.222.169 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783444667; cv=none; b=oGqxJILFdlnze70opnDpj5317I5EzColj3eeXH9XpRah8D0l6wWs3tXjswgiKnyHZlbiShda5twJKXG0uXSPypZMJE4dLvss//Sdi7M1iAdprs7vj7pVsujzjwnkZdqdZXJPypcSwO3dIuzhzy/VR/3BCoTpeYR0vAgebzFA5uU= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783444667; c=relaxed/simple; bh=nu6ZSgb2jRk2Ndie2s2jUBHTDDESXJco+T6QJqejMAk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=qXaIWVhhsUy388SYsjbu+Hp3kyk6n13MKGDKfMkEX41slsctlQlUiL5rT2aDAqJEAV7zMMBxxqsJJhNO/Mi7XZarxQmmmPctG4Hb7EXBkroxht1aVLtCMe0iTNl6FqtgNK/44zcEvux//vNzZtdhuUZ+4+Ja96JCfMG3xSSUJas= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=qkiHYXnA; arc=none smtp.client-ip=209.85.222.169 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="qkiHYXnA" Received: by mail-qk1-f169.google.com with SMTP id af79cd13be357-92e51d3d83cso228036285a.2 for ; Tue, 07 Jul 2026 10:17:46 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1783444665; x=1784049465; darn=lists.linux.dev; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to:content-type; bh=oUCStv+mG3q24BIMvpoJICyGa6vMwC+AFAbHW03keOc=; b=qkiHYXnAJpMjmUw4s7R95BMSemiesKaf6GKW+/VsX9MRvt0svavMkcZo2GONjlM7xX wb+5eHmVRfbKHktZMu1M0Bg/qouLWVDJn9BVADc8xSNc+kf5wcJrSc5oWOUrzLVSKizD F1KW64qJMVZKZN5PWqsg7Tv008JwNGrv4AS0mWycaI0i3IIdTxj5I2ZhtsZcvC43pSTp eATQeb5k5p5GgQ6SxqPSToZ9viJMyZr2i2+fmOEmW9Sd2qNvACc+5WmveaALLj/0P7tJ jflI0FVxKB4uFcv4KDWFa/ddv5/n3GobCNDK2W1kVcvkaZq5Eb9IrspST+pUEKM7bznW q6cQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1783444665; x=1784049465; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to:content-type; bh=oUCStv+mG3q24BIMvpoJICyGa6vMwC+AFAbHW03keOc=; b=lUHk5HOJmhfn5Pado9n/fLC06rTyCwx4CJsYOx28YhQ3FUg4r3MUPwx5dYfmqJ86rv DAlIJ+QQsWkcUEFnmZHggxFbsOIc0y/cBKhr1iyyqIiVzbtvAhySL5mu/6Tmu4WAO3le Z/VHS7ejo3mArxW1m0IkPV6vA1t6HuN7sgfsI9d01CXJpd4IUHwTQAgijHkVB4pM3XYD 93ArLUIPtlmTAVDQdj/eI0tM3iEG9x0VWomI7jOboVFUhI2JL5t03P0SWMdYp1FmYQ9n EVgAZSH33RAxSk/D1fXl1/OTDCM6uUa34ar6mPHWImo6X8tmCa5NMmShhb8BxKKasXKc jEtQ== X-Forwarded-Encrypted: i=1; AHgh+RqdiCWr1k4vJ6JWpTgmQwqX1wm11yWbB+wNjkVGNKFruIIMr2tsrW1VDPPE6KJPU7DD/cpr4A==@lists.linux.dev X-Gm-Message-State: AOJu0Yx1Xf1WAbjd9bA+QW9K9UFqpk+uHxNbeHJ8VmWtgHZyUw9zt1ae rnbJgDXKhIOPPrjb0WX5BSGnRxjb9lIEML4pqZp9a5x3sh7l2M6emE9O X-Gm-Gg: AfdE7cncJKNMPM2/qxgHhT5w0lSppUa3Bu9uOgGPRVElBrJtWpEqdt8rPD6tEMd4zKh 0xIvObroALGWGWSq2SYhhkFhfg1+SKg7ikXgAkL8yJczeUGqikZxrNp/GQiust6VhbHJ8GVuoy9 0SaMpY5TKI8U6uHEpH4EUTPkTkVh0gIEmfSWvdCzR2xV2JncKNvZdzYeaqnWjfD7az6nheisThV /bFStz9wSwC+SIwSCZtIGl6xrNY7OUL43jSjcA6m3jHyIRAO8SWaOWyuLOfd6WZQWfR8dPRFw0B ItH/VWT73vz2z4M0WIsGj0ayVrnDh2w13KmsPe9lt1IA5gUZnkQaw/Y/+Gx8btWV+xu2V7t7U2h PKjdkC4h45PFwPKlJh4h9tOOBiWDvs9ygviSdSWN1Z+4ng6Y1vxvUBP6QjHUKHFj3u9vlTEW4Tk rt+KCPAQzQxXTjiqJLCLP025w2nFOHi+rHKNWbloA5zOqePLUtOTRrw0NJQrZzhGcoas4O71OwZ nwmq7+UuBM7tG6jWz3je+FAnxN+LxUx X-Received: by 2002:a05:620a:4102:b0:92e:8a88:ab27 with SMTP id af79cd13be357-92ebb528e65mr702327185a.14.1783444665081; Tue, 07 Jul 2026 10:17:45 -0700 (PDT) Received: from server0.tail6e7dd.ts.net (c-68-48-65-54.hsd1.mi.comcast.net. [68.48.65.54]) by smtp.gmail.com with ESMTPSA id af79cd13be357-92e90ccde4fsm1220363385a.39.2026.07.07.10.17.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 07 Jul 2026 10:17:44 -0700 (PDT) From: Michael Bommarito To: Matthieu Baerts , Mat Martineau Cc: Geliang Tang , Paolo Abeni , Eric Dumazet , Jakub Kicinski , mptcp@lists.linux.dev, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v2] mptcp: only set DATA_FIN when a mapping is present Date: Tue, 7 Jul 2026 13:17:30 -0400 Message-ID: <20260707171730.2679013-1-michael.bommarito@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2edcb1cd-f2db-4d0c-a0e3-fd2b4dd820fe@redhat.com> References: <2edcb1cd-f2db-4d0c-a0e3-fd2b4dd820fe@redhat.com> Precedence: bulk X-Mailing-List: mptcp@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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 =3D=3D 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. Fixes: 43b54c6ee382 ("mptcp: Use full MPTCP-level disconnect state machine") Suggested-by: Paolo Abeni Cc: stable@vger.kernel.org Assisted-by: Claude:claude-opus-4-8 Signed-off-by: Michael Bommarito --- v2: adopt Paolo Abeni's suggested approach - do not set mp_opt->data_fin at all unless a mapping is present, rather than gating the consumer in mptcp_incoming_options() (v1). data_fin then defaults to the value mptcp_get_options() already clears it to (0) on the no-map path, so the uninitialized data_len/data_seq are never read. net/mptcp/options.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/mptcp/options.c b/net/mptcp/options.c index dff3fd5d3b559..6d003b24b969f 100644 --- a/net/mptcp/options.c +++ b/net/mptcp/options.c @@ -157,7 +157,6 @@ static void mptcp_parse_option(const struct sk_buff *sk= b, ptr++; flags =3D (*ptr++) & MPTCP_DSS_FLAG_MASK; - mp_opt->data_fin =3D (flags & MPTCP_DSS_DATA_FIN) !=3D 0; mp_opt->dsn64 =3D (flags & MPTCP_DSS_DSN64) !=3D 0; mp_opt->use_map =3D (flags & MPTCP_DSS_HAS_MAP) !=3D 0; mp_opt->ack64 =3D (flags & MPTCP_DSS_ACK64) !=3D 0; @@ -178,6 +177,7 @@ static void mptcp_parse_option(const struct sk_buff *sk= b, } if (mp_opt->use_map) { + mp_opt->data_fin =3D (flags & MPTCP_DSS_DATA_FIN) !=3D 0; if (mp_opt->dsn64) expected_opsize +=3D TCPOLEN_MPTCP_DSS_MAP64; else -- 2.53.0