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 E3C1A37E5D8; Thu, 20 Aug 2026 15:09:57 +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=1787238599; cv=none; b=KRmNfPlLlNMSByWhVSWxLgyg4VU86xGzeL/ypTn3oL7/xFq05TJmKji0h7KFCy3fwjtgpJ6fm+eqWZlhmb1bS37ps8QXTZ10dDi1t8fA+PST9Rd+4K8V0l1A8eat8Wh6ZQAPfHzZFuB60IDzcufl1LN/B0zq7RN24OZHUc8g6YE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787238599; c=relaxed/simple; bh=ZcK2G7Jsep6TsycxStA3sWogWd1W6VkUJB3MsU/2yRM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=fveuDpoiX/tUThOEDZGxZSmNDSOvcL0MhQEKW0m4te8pxlUp/lQgRTQF8mS/E8TO2iLFsFSf4mvRtOTjHfqFBhe78vl/URiOBA33CG7td5/IjVeWG6zqoJ5gbT+AIaaUdjCdFlRmHcT4doy+rYxLvc+YesnTZ1eqt+PPmohAotI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=OUUiR9LI; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="OUUiR9LI" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 465A91F000E9; Thu, 20 Aug 2026 15:09:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1787238597; bh=30moH52uNv36WXtMsFU2GTFK9lnVkX9+4lkHKNuuOUY=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=OUUiR9LIq+o9hwSaGW9xuSfvfAYzJEZBY/WsjkARbTye68vp7eOk9OjPd/aICq0q0 kD2AH/Qg3l37sczzFP2nXEvYyg5IxFG1Z8499Z9tAvb//HPcyjm2qALNSbvN6D3oCo i3kAd50fq5XSeZlSaXcLIfHu302RMWxmO3bbsMXA= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Wei Fang , Willem de Bruijn , Paolo Abeni , Sasha Levin Subject: [PATCH 7.1 203/228] net: tap: fix wrong transport_header when sending VLAN-tagged frame Date: Thu, 20 Aug 2026 16:55:45 +0200 Message-ID: <20260820145251.202146450@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260820145244.450574346@linuxfoundation.org> References: <20260820145244.450574346@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 7.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Wei Fang [ Upstream commit cbb35cbe8db268fefe34c23df15348cf99025298 ] In tap_get_user_xdp(), when processing a VLAN-tagged frame (e.g. ETH_P_8021Q), skb_set_network_header() is called first to advance network_header past the VLAN tag to the inner protocol header. skb_probe_transport_header() is then called with skb->protocol still set to ETH_P_8021Q, while nhoff (derived from skb_network_offset()) already points past the VLAN tag to the inner protocol header. In __skb_flow_dissect(), proto is initialized to ETH_P_8021Q and nhoff points past the VLAN tag. When the dissector hits case ETH_P_8021Q, it reads a struct vlan_hdr at the current nhoff via __skb_header_pointer(), but that offset contains the inner protocol header (e.g. an IP header). The bytes are misinterpreted as a VLAN header, yielding a garbage encapsulated EtherType that matches no known protocol. The dissector returns false, so skb_probe_transport_header() never calls skb_set_transport_header(), leaving transport_header at its uninitialized sentinel value (~0U). Move skb_set_network_header() to after skb_probe_transport_header(). At the time skb_probe_transport_header() is called, network_header still points to the VLAN header (offset ETH_HLEN), so nhoff is correct and the flow dissector can parse the VLAN header, extract the inner EtherType, and advance nhoff to the inner protocol header, allowing transport_header to be set correctly. Fixes: 8c76e77f9069 ("tap: call skb_probe_transport_header after setting skb->dev") Assisted-by: WChat:claude-opus-4-8 Signed-off-by: Wei Fang Reviewed-by: Willem de Bruijn Link: https://patch.msgid.link/20260807063405.688780-3-wei.fang@oss.nxp.com Signed-off-by: Paolo Abeni Signed-off-by: Sasha Levin --- drivers/net/tap.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/net/tap.c b/drivers/net/tap.c index 5d2d34d24ce81..9b5af08cdd479 100644 --- a/drivers/net/tap.c +++ b/drivers/net/tap.c @@ -1091,12 +1091,13 @@ static int tap_get_user_xdp(struct tap_queue *q, struct xdp_buff *xdp) } } + skb_probe_transport_header(skb); + /* Move network header to the right position for VLAN tagged packets */ if (eth_type_vlan(skb->protocol) && vlan_get_protocol_and_depth(skb, skb->protocol, &depth) != 0) skb_set_network_header(skb, depth); - skb_probe_transport_header(skb); dev_queue_xmit(skb); rcu_read_unlock(); -- 2.53.0