From 55787a73fbb61cd385264fe4500c9fca352fa899 Mon Sep 17 00:00:00 2001 From: Jianbo Liu Date: Thu, 20 Nov 2025 05:56:09 +0200 Subject: [PATCH] xfrm: Fix inner mode lookup in tunnel mode GSO segmentation [ Upstream commit 3d5221af9c7711b7aec8da1298c8fc393ef6183d ] Commit 61fafbee6cfe ("xfrm: Determine inner GSO type from packet inner protocol") attempted to fix GSO segmentation by reading the inner protocol from XFRM_MODE_SKB_CB(skb)->protocol. This was incorrect because the field holds the inner L4 protocol (TCP/UDP) instead of the required tunnel protocol. Also, the memory location (shared by XFRM_SKB_CB(skb) which could be overwritten by xfrm_replay_overflow()) is prone to corruption. This combination caused the kernel to select the wrong inner mode and get the wrong address family. The correct value is in xfrm_offload(skb)->proto, which is set from the outer tunnel header's protocol field by esp[4|6]_gso_encap(). It is initialized by xfrm[4|6]_tunnel_encap_add() to either IPPROTO_IPIP or IPPROTO_IPV6, using xfrm_af2proto() and correctly reflects the inner packet's address family. Fixes: 61fafbee6cfe ("xfrm: Determine inner GSO type from packet inner protocol") Signed-off-by: Jianbo Liu Reviewed-by: Sabrina Dubroca Signed-off-by: Steffen Klassert Signed-off-by: Sasha Levin --- net/ipv4/esp4_offload.c | 4 ++-- net/ipv6/esp6_offload.c | 4 ++-- 2 files changed, 4 insertions(+), 4 deletions(-) diff --git a/net/ipv4/esp4_offload.c b/net/ipv4/esp4_offload.c index 11e33a431267..028d2d3477d1 100644 --- a/net/ipv4/esp4_offload.c +++ b/net/ipv4/esp4_offload.c @@ -111,8 +111,8 @@ static struct sk_buff *xfrm4_tunnel_gso_segment(struct xfrm_state *x, struct sk_buff *skb, netdev_features_t features) { - const struct xfrm_mode *inner_mode = xfrm_ip2inner_mode(x, - XFRM_MODE_SKB_CB(skb)->protocol); + struct xfrm_offload *xo = xfrm_offload(skb); + const struct xfrm_mode *inner_mode = xfrm_ip2inner_mode(x, xo->proto); __be16 type = inner_mode->family == AF_INET6 ? htons(ETH_P_IPV6) : htons(ETH_P_IP); diff --git a/net/ipv6/esp6_offload.c b/net/ipv6/esp6_offload.c index 438f9cbdca29..333d87557bf3 100644 --- a/net/ipv6/esp6_offload.c +++ b/net/ipv6/esp6_offload.c @@ -145,8 +145,8 @@ static struct sk_buff *xfrm6_tunnel_gso_segment(struct xfrm_state *x, struct sk_buff *skb, netdev_features_t features) { - const struct xfrm_mode *inner_mode = xfrm_ip2inner_mode(x, - XFRM_MODE_SKB_CB(skb)->protocol); + struct xfrm_offload *xo = xfrm_offload(skb); + const struct xfrm_mode *inner_mode = xfrm_ip2inner_mode(x, xo->proto); __be16 type = inner_mode->family == AF_INET ? htons(ETH_P_IP) : htons(ETH_P_IPV6);