From: Kyle Zeng <kylebot@openai.com> mainline inclusion from mainline-v7.2-rc1 commit f0e42f0c4337b1f220de1ddd63f47197c7dee4de category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/15914 CVE: CVE-2026-53228 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- ipip6_tunnel_xmit() caches the inner IPv6 header pointer at function entry and continues using it after iptunnel_handle_offloads(). For GSO skbs, iptunnel_handle_offloads() calls skb_header_unclone(). When the skb header is cloned, skb_header_unclone() can call pskb_expand_head(), which may move the skb head. The pskb_expand_head() contract requires pointers into the skb header to be reloaded after the call. If the later skb_realloc_headroom() branch is not taken, SIT uses the stale iph6 pointer to read the inner hop limit and DS field. That can read from a freed skb head after the old head's remaining clone is released. Reload iph6 after the offload helper succeeds and before subsequent reads from the inner IPv6 header. Keep the existing reload after skb_realloc_headroom(), since that branch can also replace the skb. Fixes: 14909664e4e1 ("sit: Setup and TX path for sit/UDP foo-over-udp encapsulation") Signed-off-by: Kyle Zeng <kylebot@openai.com> Reviewed-by: Eric Dumazet <edumazet@google.com> Reported-by: syzbot+6eb9ca986d80f6f88cf9@syzkaller.appspotmail.com Link: https://patch.msgid.link/20260605073448.6524-1-kylebot@openai.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> Conflicts: net/ipv6/sit.c [context differs: fe8570186f10 use dst4_mtu() in ipip6_tunnel_xmit(), which is not backport] Signed-off-by: Dong Chenchen <dongchenchen2@huawei.com> --- net/ipv6/sit.c | 1 + 1 file changed, 1 insertion(+) diff --git a/net/ipv6/sit.c b/net/ipv6/sit.c index 6799691f565c..0de46ad81f62 100644 --- a/net/ipv6/sit.c +++ b/net/ipv6/sit.c @@ -925,6 +925,7 @@ static netdev_tx_t ipip6_tunnel_xmit(struct sk_buff *skb, ip_rt_put(rt); goto tx_error; } + iph6 = ipv6_hdr(skb); if (df) { mtu = dst_mtu(&rt->dst) - t_hlen; -- 2.43.0