From: Eric Dumazet Date: Mon, 25 May 2026 20:36:42 +0000 (+0000) Subject: vxlan: do not reuse cached ip_hdr() value after skb_tunnel_check_pmtu() X-Git-Tag: v7.1-rc6~27^2~12 X-Git-Url: http://git.ipfire.org/gitweb/index.cgi?a=commitdiff_plain;h=7d9ef0cb271555d8cf39fefe6c981e1493b25ecf;p=thirdparty%2Fkernel%2Flinux.git vxlan: do not reuse cached ip_hdr() value after skb_tunnel_check_pmtu() skb_tunnel_check_pmtu() can change skb->head. Reusing old_iph afer skb_tunnel_check_pmtu() can cause an UAF. Use instead ip_hdr(skb) as done in drivers/net/bareudp.c and drivers/net/geneve.c. Found by Sashiko. Fixes: 4cb47a8644cc ("tunnels: PMTU discovery support for directly bridged IP packets") Signed-off-by: Eric Dumazet Reviewed-by: Stefano Brivio Link: https://patch.msgid.link/20260525203642.2389723-1-edumazet@google.com Signed-off-by: Jakub Kicinski --- diff --git a/drivers/net/vxlan/vxlan_core.c b/drivers/net/vxlan/vxlan_core.c index e88798497503..b5b1253ac08b 100644 --- a/drivers/net/vxlan/vxlan_core.c +++ b/drivers/net/vxlan/vxlan_core.c @@ -2531,7 +2531,7 @@ void vxlan_xmit_one(struct sk_buff *skb, struct net_device *dev, goto out_unlock; } - tos = ip_tunnel_ecn_encap(tos, old_iph, skb); + tos = ip_tunnel_ecn_encap(tos, ip_hdr(skb), skb); ttl = ttl ? : ip4_dst_hoplimit(&rt->dst); err = vxlan_build_skb(skb, ndst, sizeof(struct iphdr), vni, md, flags, udp_sum); @@ -2605,7 +2605,7 @@ void vxlan_xmit_one(struct sk_buff *skb, struct net_device *dev, goto out_unlock; } - tos = ip_tunnel_ecn_encap(tos, old_iph, skb); + tos = ip_tunnel_ecn_encap(tos, ip_hdr(skb), skb); ttl = ttl ? : ip6_dst_hoplimit(ndst); skb_scrub_packet(skb, xnet); err = vxlan_build_skb(skb, ndst, sizeof(struct ipv6hdr),