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 21F337404E; Sat, 17 Oct 2026 16:33:50 +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=1792254831; cv=none; b=HeD45+bR59dbiedayPFcSkoEOiJgiCZcA2dyiJRweEHZuwzosJdYj+5x/xAMVqkQ8C2ytBxedQhYSefU/iwEXzzwZaUer5rCy7l5ged2lh34BDpcvbvYHLeFrpcxkL4/TJTd+r2ME7AfFbynzhhxjuYu3Umx6xA3tW1XVhIF3VA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792254831; c=relaxed/simple; bh=BYfjwRPGGQHumeNPDHpaRe9BYb0oKH2Or43nFOcyvao=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=u52NDrtxWP3VBKUm31SqJ0j4OHFISDh4hQvJblevnrWfzWU9F5h/9oOL699/X9ihRvDxGWG3g8FyPUtndeTAW9cUBETIS9rXe3nrPd5XhBnN5ATHxv5Y0m8mWE0yV90nRwuhZmzZY9SR4A9e6IXrmr8N3+HykGDeKSSOLbJSkGI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=L72Gh0Os; 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="L72Gh0Os" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7A1C31F000C4; Sat, 17 Oct 2026 16:33:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1792254830; bh=NlHfTbj8+iZYWCERJPPvf8z66oLk1IMqpHfm1Zs+I7M=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=L72Gh0OsGKTCz16JPEcIHlQQ2mArV4RHD2EQobBt39tywqDc58PKRyMuBHowJhr19 3qG8dR+MYjan8/k1655LbKbnvdf9UPYDmf3unoSNdRoSIAj/c8ZCzvOpoxta7pKVkl yIqEumVJXZzNQrZ1JlE+fWAagcaDuDBo47l2oaZQ= 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 6.12 559/869] net: tap: fix wrong transport_header when sending VLAN-tagged frame Date: Sat, 17 Oct 2026 17:56:40 +0200 Message-ID: <20261017160051.412277255@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261017160036.979869304@linuxfoundation.org> References: <20261017160036.979869304@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 6.12-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 d5a1ab9b2a37d..fcc9d135c5fc2 100644 --- a/drivers/net/tap.c +++ b/drivers/net/tap.c @@ -1208,12 +1208,13 @@ 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