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 7ED013B582F; Fri, 9 Oct 2026 14:34:48 +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=1791556489; cv=none; b=MFf2/xmyzLC1XAlLMh2JFl9G89mtqLQdIzILDsGZySr8szAmcqaSTRcc9qHKHcEEIrCCxVziuttS2o+TsWAzWCutkjAg4/Gqby+m5UN2HmVJAWXzFU22QFkcJ5K0Ixpyov4kDKGIAgWSb0OA52J6hjH1JNjM6EiSYpQcvmWTpZY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791556489; c=relaxed/simple; bh=dlK13NHmJ3MVEr59YO2ppUF5z69yJAqy2rTz1+GLux8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=KWFsamuPVDA7jWF4ZVNFXQINSSjARLrdwZKaLOdNfpbV1pdksuZXm3qzOEy68zTPSEwBfq6AJhCdWAgPo6q2+ws1/cC2VBbO4Og7688m/Qrx0ceTclHw+LVrQjQAYDxVVMaT9GBFxzbD2tuyrZ/QAwpF+7A1XepE02WtYc7lG2I= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=y+LKZuSa; 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="y+LKZuSa" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D90281F00898; Fri, 9 Oct 2026 14:34:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1791556488; bh=MY0lsXIqzcyrPHO5DDOUs4bnnah+zRy81InQKh/y44E=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=y+LKZuSa9j+M5HCxL8fkiHaVmc5FzlSdplEhIbA72r3/q9+ycZtChEwr740r4+3na AWSXR4KjlzcZj0hdvqjsPnfBcIuD6qqdQjmZ8NPMyBhM2Y+TkA4uxHalSI3pLRpvAv cm1LmEDm06XJondqEX88KhvYbHCt9C8juHE1eaus= 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 6.18 243/403] net: extend IPv6 exthdr detection of tunneled packets Date: Fri, 9 Oct 2026 16:10:04 +0200 Message-ID: <20261009140957.849680715@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261009140952.119038291@linuxfoundation.org> References: <20261009140952.119038291@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 6.18-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 22b90820d2c7d..10e02845fea44 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -3756,20 +3756,36 @@ 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, @@ -3824,7 +3840,7 @@ 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); @@ -3927,8 +3943,7 @@ 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