Commit 7d9ef0cb authored by Eric Dumazet's avatar Eric Dumazet Committed by Jakub Kicinski
Browse files

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: 4cb47a86 ("tunnels: PMTU discovery support for directly bridged IP packets")
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Reviewed-by: default avatarStefano Brivio <sbrivio@redhat.com>
Link: https://patch.msgid.link/20260525203642.2389723-1-edumazet@google.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent b4bc9435

drivers/net/vxlan/vxlan_core.c

+2 −2
Original line number Diff line number Diff line
@@ -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),