From 6973a21ee73c5567f883813c8ef414774b45892f Mon Sep 17 00:00:00 2001 From: Zhiling Zou Date: Mon, 3 Aug 2026 21:28:58 +0800 Subject: [PATCH] ipv6: xfrm: use full sockets in local error paths xfrm6_local_rxpmtu() and xfrm6_local_error() dereference skb->sk as if it always pointed at a full IPv6 socket. That is not guaranteed. TCP SYN-ACK skbs can be owned by a TCP_NEW_SYN_RECV request_sock while the output path itself is driven by the full listener. If rerouting selects an IPv6 XFRM tunnel route with a lower MTU, the local PMTU/error handling path can reach these callbacks with that mini-socket still attached to the skb. The callbacks then miscast the request socket as a full inet/IPv6 socket and can read beyond the request_sock allocation when they access inet_sock or ipv6_pinfo state. Resolve the owner with skb_to_full_sk() in both callbacks and bail out when no full socket is attached. This matches the surrounding XFRM IPv6 PMTU/error logic, which already reasons about full sockets with skb_to_full_sk(). Fixes: dd767856a36e ("xfrm6: Don't call icmpv6_send on local error") Cc: stable@vger.kernel.org Reported-by: Vega Signed-off-by: Zhiling Zou Signed-off-by: Steffen Klassert --- net/ipv6/xfrm6_output.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/net/ipv6/xfrm6_output.c b/net/ipv6/xfrm6_output.c index 512bdaf13699..44b221a09a0c 100644 --- a/net/ipv6/xfrm6_output.c +++ b/net/ipv6/xfrm6_output.c @@ -19,7 +19,10 @@ void xfrm6_local_rxpmtu(struct sk_buff *skb, u32 mtu) { struct flowi6 fl6; - struct sock *sk = skb->sk; + struct sock *sk = skb_to_full_sk(skb); + + if (!sk) + return; fl6.flowi6_oif = sk->sk_bound_dev_if; fl6.daddr = ipv6_hdr(skb)->daddr; @@ -31,7 +34,10 @@ void xfrm6_local_error(struct sk_buff *skb, u32 mtu) { struct flowi6 fl6; const struct ipv6hdr *hdr; - struct sock *sk = skb->sk; + struct sock *sk = skb_to_full_sk(skb); + + if (!sk) + return; hdr = skb->encapsulation ? inner_ipv6_hdr(skb) : ipv6_hdr(skb); fl6.fl6_dport = inet_sk(sk)->inet_dport;