From 04c20a9356f283da623903e81e7c6d5df7e4dc3c Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Beno=C3=AEt=20Monin?= Date: Thu, 24 Oct 2024 16:01:54 +0200 Subject: [PATCH] net: skip offload for NETIF_F_IPV6_CSUM if ipv6 header contains extension MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit As documented in skbuff.h, devices with NETIF_F_IPV6_CSUM capability can only checksum TCP and UDP over IPv6 if the IP header does not contains extension. This is enforced for UDP packets emitted from user-space to an IPv6 address as they go through ip6_make_skb(), which calls __ip6_append_data() where a check is done on the header size before setting CHECKSUM_PARTIAL. But the introduction of UDP encapsulation with fou6 added a code-path where it is possible to get an skb with a partial UDP checksum and an IPv6 header with extension: * fou6 adds a UDP header with a partial checksum if the inner packet does not contains a valid checksum. * ip6_tunnel adds an IPv6 header with a destination option extension header if encap_limit is non-zero (the default value is 4). The thread linked below describes in more details how to reproduce the problem with GRE-in-UDP tunnel. Add a check on the network header size in skb_csum_hwoffload_help() to make sure no IPv6 packet with extension header is handed to a network device with NETIF_F_IPV6_CSUM capability. Link: https://lore.kernel.org/netdev/26548921.1r3eYUQgxm@benoit.monin/T/#u Fixes: aa3463d65e7b ("fou: Add encap ops for IPv6 tunnels") Signed-off-by: Benoît Monin Reviewed-by: Willem de Bruijn Link: https://patch.msgid.link/5fbeecfc311ea182aa1d1c771725ab8b4cac515e.1729778144.git.benoit.monin@gmx.fr Signed-off-by: Jakub Kicinski --- net/core/dev.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/net/core/dev.c b/net/core/dev.c index ea5fbcd133ae..8453e14d301b 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -3639,6 +3639,9 @@ 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)) + goto sw_checksum; switch (skb->csum_offset) { case offsetof(struct tcphdr, check): case offsetof(struct udphdr, check): @@ -3646,6 +3649,7 @@ int skb_csum_hwoffload_help(struct sk_buff *skb, } } +sw_checksum: return skb_checksum_help(skb); } EXPORT_SYMBOL(skb_csum_hwoffload_help);