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 DA9EC4F7983; Tue, 13 Oct 2026 12:39:48 +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=1791895190; cv=none; b=AcB/xWrTFpNMZZ9v9eQe2HrbxYVaQip8kp9QrJ5+L25cFSWtXb1Qbf1Qxbkg5rVB1Cp5t4xWwav8hqkaa3FfzhfdxaK8w9uT+cX8xmi90KOJJenoDqQ2cXq7ySWgiY7NyCVnEBosp4gfxhixtauBkEbVfvYPwEgHj1pW7H+DcsM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791895190; c=relaxed/simple; bh=lOMNmUTqS2RLxL9gdU/wlKiPRAeEIPK4a/+EzqgrTnM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=hJD6FdGLKnDKlgEZjyCwp1HAaWHddVCrt8jwV+JvZ0s13+QNfVrypdCg5X9i/GYvEoWruR8yunbAmPzcVh4KQ6i/Kzt3sdegsh1/PpH1wRgAsBycd6YcabfDYz1488MdSHTWzQp2tfoBKxkI0Li5asOid8xoJRwLERFeFzkjItk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=sEa/NnOm; 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="sEa/NnOm" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 38C781F0089A; Tue, 13 Oct 2026 12:39:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1791895188; bh=4FrvmTVxF+KfXahp8eS71ikmWcjREKQviKJ1RyWHkow=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=sEa/NnOmhIDhD3bgzZISjz1eQXJg3O/bGqD14ywueUwz3A4r5K1aUBtl2YsF8r4bx ePgbdCpSbD52lVFe7aO+RN3VINV7hWGUDXTVq3WQkj/722CCWsuWFx+mwkt70T1Nc0 fuMXzTa0vhfjj0j/D4LiUKVkeU80SyvgIRZXQRCQ= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Willem de Bruijn , Jakub Kicinski , Sasha Levin Subject: [PATCH 6.12 192/497] net: extend IPv6 exthdr detection of tunneled packets Date: Tue, 13 Oct 2026 13:35:59 +0200 Message-ID: <20261013112912.449287077@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261013112907.864180619@linuxfoundation.org> References: <20261013112907.864180619@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: Willem de Bruijn [ Upstream commit 5f0764cb1c81a9712bce605d38efe6d844a70b29 ] Commit c4336a07eb6b ("net: correctly handle tunneled traffic on IPV6_CSUM GSO fallback") split skb_gso_has_extension_hdr() into mutually exclusive branches on skb->encapsulation. This did not yet address all paths: 1. With skb->encapsulation set, the outer header is not checked. IPv6 tunnels such as ip6_gre and ip6_tunnel add an outer Destination Options header by default (encap_limit). Their GSO packets skip software GSO, then skb_csum_hwoffload_help() sees the outer extension header and calls skb_checksum_help() on the GSO skb, which warns and drops it. 2. Tunnels over IPv6 without an outer transport header, such as ip6_tunnel, leave skb->transport_header at the inner transport header. skb_network_header_len() then spans the outer IPv6, tunnel and inner IP headers, a false positive. 3. UDP tunnels without an inner network header, such as SCTP-in-UDP or PSP, have no inner IPv6 header to check. Decide on the outer header alone. 4. Directly dereferencing inner_ip_hdr(skb)->version without skb_header_pointer() is unsafe. Instead, check ipv6_ext_hdr(nexthdr) on the outer IPv6 header and, if set, on the inner IPv6 header. Read the headers with skb_header_pointer(). Keep the skb_network_header_len() check when !skb->encapsulation to also catch encapsulated packets without skb->encapsulation (e.g., virtio). Use the same helper in skb_csum_hwoffload_help(). Its open coded test has the false positive of (2) and ignores the inner header. Background: checksum offload of tunneled packets invariants: Non-GSO skb: - If the inner packet is CHECKSUM_PARTIAL, Local Checksum Offload computes the outer checksum in software and the device offloads only the inner L4 checksum. - If the inner packet is CHECKSUM_NONE (e.g., SCTP-in-UDP, ESP-in-UDP, Remote Checksum Offload), the device offloads the outer UDP or GRE checksum instead. GSO skb: - A device with NETIF_F_GSO_UDP_TUNNEL_CSUM or NETIF_F_GSO_GRE_CSUM computes both inner and outer checksums per segment. The outer checksum is seeded with only the pseudo-header checksum. A NETIF_F_IPV6_CSUM device must parse through the outer headers to reach the inner ones. Fixes: c4336a07eb6b ("net: correctly handle tunneled traffic on IPV6_CSUM GSO fallback") Cc: stable@vger.kernel.org Signed-off-by: Willem de Bruijn Link: https://patch.msgid.link/20260926140506.2335137-1-willemdebruijn.kernel@gmail.com Signed-off-by: Jakub Kicinski [ sashal: kept the !ipv6_has_hopopt_jumbo() exemptions; this tree still inserts the BIG TCP HBH jumbo header ] Signed-off-by: Sasha Levin --- net/core/dev.c | 49 ++++++++++++++++++++++++++++++++----------------- 1 file changed, 32 insertions(+), 17 deletions(-) diff --git a/net/core/dev.c b/net/core/dev.c index a4554020076f4..48f099f9e804c 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -3579,20 +3579,36 @@ static netdev_features_t dflt_features_check(struct sk_buff *skb, return vlan_features_check(skb, features); } -static bool skb_gso_has_extension_hdr(const struct sk_buff *skb) -{ - if (!skb->encapsulation) - return ((skb_shinfo(skb)->gso_type & SKB_GSO_TCPV6 || - (skb_shinfo(skb)->gso_type & SKB_GSO_UDP_L4 && - vlan_get_protocol(skb) == htons(ETH_P_IPV6))) && - skb_transport_header_was_set(skb) && - skb_network_header_len(skb) != sizeof(struct ipv6hdr)); - else - return (!skb_inner_network_header_was_set(skb) || - ((skb_shinfo(skb)->gso_type & SKB_GSO_TCPV6 || - (skb_shinfo(skb)->gso_type & SKB_GSO_UDP_L4 && - inner_ip_hdr(skb)->version == 6)) && - skb_inner_network_header_len(skb) != sizeof(struct ipv6hdr))); +static bool __skb_has_ipv6_ext_hdr(const struct sk_buff *skb, int nhoff) +{ + const struct ipv6hdr *ip6h; + struct ipv6hdr _ip6h; + + ip6h = skb_header_pointer(skb, nhoff, sizeof(_ip6h), &_ip6h); + return ip6h && ip6h->version == 6 && ipv6_ext_hdr(ip6h->nexthdr); +} + +static bool skb_has_ipv6_extension_hdr(const struct sk_buff *skb) +{ + if (vlan_get_protocol(skb) == htons(ETH_P_IPV6)) { + if (__skb_has_ipv6_ext_hdr(skb, skb_network_offset(skb))) + return true; + + /* Catch tunnels without skb->encapsulation (e.g., virtio). */ + if (!skb->encapsulation && + skb_transport_header_was_set(skb) && + skb_network_header_len(skb) != sizeof(struct ipv6hdr)) + return true; + } + + /* Tunnels without an inner network header, such as SCTP-in-UDP or + * PSP, have no inner IP header and thus no inner extension header. + */ + if (skb->encapsulation && skb_inner_network_header_was_set(skb) && + __skb_has_ipv6_ext_hdr(skb, skb_inner_network_offset(skb))) + return true; + + return false; } static netdev_features_t gso_features_check(const struct sk_buff *skb, @@ -3641,7 +3657,7 @@ static netdev_features_t gso_features_check(const struct sk_buff *skb, * so neither does TSO that depends on it. */ if (features & NETIF_F_IPV6_CSUM && - skb_gso_has_extension_hdr(skb) && + skb_has_ipv6_extension_hdr(skb) && !ipv6_has_hopopt_jumbo(skb)) features &= ~(NETIF_F_IPV6_CSUM | NETIF_F_TSO6 | NETIF_F_GSO_UDP_L4); @@ -3744,8 +3760,7 @@ int skb_csum_hwoffload_help(struct sk_buff *skb, return 0; if (features & (NETIF_F_IP_CSUM | NETIF_F_IPV6_CSUM)) { - if (vlan_get_protocol(skb) == htons(ETH_P_IPV6) && - skb_network_header_len(skb) != sizeof(struct ipv6hdr) && + if (skb_has_ipv6_extension_hdr(skb) && !ipv6_has_hopopt_jumbo(skb)) goto sw_checksum; -- 2.53.0