From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=74.125.229.8 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1792660508; b=oN3K58CdPbT1EoWeaNmtYXyNbQKXVd0wVgOiwVKAClc8raApDSRTVEMRbSIueqA7h1DW A10VVPe8TDXbWqAz6uxKVtTnB/ZAcYqlFIQRjbKRA6peghVbnGsezsASzpf5RvmI7FxPY aZa/33FgiasqM6OQhl8WkZZRERZixIA1mWfxvrQOVK7Mh/8eBm7O1NUTIC8cd8nkL0MPv 2XRLmA2AAxn2Ao+beZJheRjGhhZqE+CbbgKnwUkW1RyWSb0SIvs7sHhckfofIWj1rlUVN UHMwUfC+4+5A77oIsTey/t61XJBbTXpDPv0dGmbXvDU6n5fmnv/0Mu8nTnTSmVjXM/A== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1792660508; h=DMARC-Filter:Received:DKIM-Signature:X-Google-DKIM-Signature: X-Forwarded-Encrypted:X-Gm-Message-State:X-Gm-Gg:X-Received:Received: From:To:Cc:Subject:Date:Message-Id:X-Mailer:MIME-Version:Content-Type: Content-Transfer-Encoding; bh=e7NVZjs7NMYnhNT7+IbNDUXDeXgt96yTHJb2bsDwWM4=; b=rieFPFTvkUrfmlPUr0KRYLYEfkuFCEBvLNjR7I1E+DFqbBjojSJs/DcI2inMUaGFL8CM yvqdzt+JIUpheYhBeTLxB439nUCuWnbGlfxBHCXdDUruprTjRE1gygrDyFEbpBayw7C91 vNSYJ6+Cm2avk6kRRM6Y3+UXnScHEFCu0ToY2GmWPtsuIDpn6SNGioLlwbvAARnf41f4w Zr0MblVQ40z/vpLr08W/aOWT5fYnVlqCvPfRfrR8a7DIzTkrmZzC6Z/eaebyrcMtGHOrc PNaqU9lyNblN0tFUN1+vObh0+AQgfzFsZTJ+RBpFTvLF2p0ZUmGDgw1Vdqgtq4BE8zA== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass header.d=gmail.com header.i=@gmail.com header.a=rsa-sha256 header.s=20251104 header.b=QhriTMCq; arc=none smtp.remote-ip=74.125.229.8 Received: from mail-dy2-f8.google.com (mail-dy2-f8.google.com [74.125.229.8]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 55884606A321 for ; Thu, 22 Oct 2026 09:15:08 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 55884606A321 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, unprotected) header.d=gmail.com header.i=@gmail.com header.a=rsa-sha256 header.s=20251104 header.b=QhriTMCq Received: by mail-dy2-f8.google.com with SMTP id 5a478bee46e88-33baa8eb238so947439eec.0 for ; Thu, 22 Oct 2026 02:15:08 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1792660507; x=1793265307; darn=vger.kernel.org; h=content-transfer-encoding:content-type:mime-version:message-id:date :subject:cc:to:from:from:to:cc:subject:date:message-id:reply-to :content-type; bh=e7NVZjs7NMYnhNT7+IbNDUXDeXgt96yTHJb2bsDwWM4=; b=QhriTMCqanFSHGj1/mrQRgaQJRQT0WGi/+TulRag7c9OqGnMfhLtzqL2CQSYXPG6Oq 2oXDyR0DXl0LFIusx1pdmqEn8ORXXo3WHfTKUJkOTpqyQ2l4Lo7nAJ7cdorxLVTMt419 bBErp20v5DH8EY/5Uev9R9XizbWPirgqzHl+Deo4lLIXIC3YR/FFIidiPdAFsPH+tdL6 FsSFXG36ym2ubJdn8vDk2n+2J5jSlBlidpM/Fz+5IsAGCMBT+nZtrCjbWVadua/1zQHk pBMwq5kn1ZMVnBMMLWvcGu+or+/yplXBh0AmfpP7Ew4YpLYohlDAzgJCfDJrzJp05Wam mMMg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1792660507; x=1793265307; h=content-transfer-encoding:content-type:mime-version: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=e7NVZjs7NMYnhNT7+IbNDUXDeXgt96yTHJb2bsDwWM4=; b=TFT59BbHdGwwtpFhCxKF3DkOcNrnwsfYYOCBRMo1DRKj998OOnzveuTMkW2btJTXKE 6azVm4NUuq/9IyzxW0Skh6/Vg7Zx1HxIjMuYh3sZ+Vc+QaD5vnTqzKCAF0vaApnBz5Bn RF5p9edAoJuFtv0cq1Isg+rmUAu1F6Rf9eYFneANLXhJAoOiLU7m00CeQuHgzF53nQuy tL4RXpk7DPr2yv6HoqUHM7FF88k0Yy9+PclVmCy54hKnC6LSO1qsj4ufvSlDO24N6kh/ 1SR7QvcYjhJgwpWKtpTFkkgHPNPur1Hw9JHpzD0OFoSJGnLlC4CuoHBQs91ifIb4p8zP mOHw== X-Forwarded-Encrypted: i=1; AKwUvBzNafgXV7lD7gVCJj0kwkBn+NFCVG+luUqoiKCDxY1JeXB/WKI8UpTDc97Ng6h3jZLI3x6GaY4Dp/3Jaqw=@vger.kernel.org X-Gm-Message-State: AFq9FYKtYyUHaCH5/db2GCiDIhkZ2LSCiBsBtbyet0PXMzbnumniRFsK 7WkktsLRklR2dBjEeupZjvQRwVbuGMPjEXOnWoJAS4XmtukbebPAzFWH X-Gm-Gg: AYBFou0u80hg9Y6xjh/gMBlFWLlSAXCjOuHriqh8yjlfuV848t0bO42k50+R1CH6SDE 7OG7hrWcVrcypUXGdCV+lhG+ajPS9ppRFF8ms7BGT6Ib0aXP/yMxt1bx32I0aryr51/YBSCPZGm FjuYCYfrUsP0Ko8yu6kKKjT0IdiEwPNeTRTahoxAc3CIv3ALefcFnXU/S/IsqDg1wWobBpm5eig +d0njB4TqvQbx5WM7BRQWWQZGd+dpqxsWYXXpEGRVqH2mIgDvvhKRGSG/WwhrwmTgx39dJjI3lN disnZ8Fm8GvJr+ZyM9YTFq4zF/WKvAMbhLiUKFp9N9f1ymMnjQ85OZo9d9aVqktcpwUPjIIEgYm kvSV+dNj3+ydbLQ2iMYyyI1HQS6n5EFnCpEvbQq+DPEFDZg9UxvBr8iB5s7608qv7qmLb+q5jGr UK0qJywlG3aZro5CG4vVSuKD/taoIEUzIFSnBgHUaV/F/UWWV2FGlvpiOLrgoCKeWVbufUEMDct pdbU4Jc/4pVDscfWoByAacBT7Q4ZH67vZ59hPcrT0SBZ98QdtXJ8p2Ds+dQlCBrWWAvRi18gb1t ZnGuGWxwRorololRKOeVbORDkTgIEy6keO+Lq5Z2 X-Received: by 2002:a05:693c:4199:10b0:35e:1807:cedf with SMTP id 5a478bee46e88-3674a405bbamr7360868eec.1.1792660507440; Thu, 22 Oct 2026 02:15:07 -0700 (PDT) Received: from youngkk-vm.localdomain (67.216.200.102.16clouds.com. [67.216.200.102]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-36740cca3d8sm14612471eec.14.2026.10.22.02.15.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 22 Oct 2026 02:15:06 -0700 (PDT) From: Cheng Yongkang To: Nikolay Aleksandrov , Ido Schimmel Cc: "David S . Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , bridge@lists.linux.dev, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [BUG] net: bridge: MST bypasses blocking when VLAN filtering is off Date: Thu, 22 Oct 2026 02:15:01 -0700 Message-Id: <20261022091501.3650765-1-teel4res@gmail.com> X-Mailer: git-send-email 2.34.1 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Hi all, MST can be enabled while VLAN filtering is disabled and no port VLAN entries exist. nbp_vlan_init() still installs a port VLAN group, so br_mst_is_enabled() returns true even though BROPT_VLAN_ENABLED is off. With that configuration: ingress skips the normal p->state check and forces forwarding br_allowed_ingress() accepts the unfiltered frame br_allowed_egress() accepts the unfiltered frame A port in BR_STATE_BLOCKING therefore still forwards data in both directions. STP/MRP loop protection is defeated. Observed on Linux v7.3, commit 08ab31164c55f20c7a2653de3186ae333470e2c1, with vlan_filtering=0, default_pvid=0, mst_enabled=1, and a port whose IFLA_BRPORT_STATE read back as BR_STATE_BLOCKING: MST on: egress=3 ingress=3 MST off: egress=0 ingress=0 MST on: egress=3 ingress=3 Each direction sent three matching broadcast frames. This is a deterministic configuration/state mismatch, not a race. The MST fast path should require both MST and VLAN filtering, while retaining the existing non-NULL port VLAN-group lifetime check. The MST configuration itself should also be rejected if it is unusable with VLAN filtering disabled. CVE-2025-40297 used the same broad predicate for a port-deletion UAF, but its fix only added the vlgrp lifetime check. The normal data-plane forwarding bypass remains in current source; I found no separate fix or CVE. The test used a diagnostic switchdev endpoint only to establish the MRP ring state. It did not replace bridge, VLAN, MST or packet-forwarding code. The PoC and full program/console logs are available on request. This was found with a multi-agent workflow; the forwarding differential was reproduced in QEMU. Thanks, Cheng Yongkang