xfrm6: Fix transport header offset in _decode_session6.

skb->transport_header might not be valid when we do a reverse
decode because the ipv6 tunnel error handlers don't update it
to the inner transport header. This leads to a wrong offset
calculation and to wrong layer 4 informations. We fix this
by using the size of the ipv6 header as the first offset.

Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/net/ipv6/xfrm6_policy.c b/net/ipv6/xfrm6_policy.c
index 5f983644373a..aa48302f00a1 100644
--- a/net/ipv6/xfrm6_policy.c
+++ b/net/ipv6/xfrm6_policy.c
@@ -130,8 +130,8 @@ _decode_session6(struct sk_buff *skb, struct flowi *fl, int reverse)
 {
         struct flowi6 *fl6 = &fl->u.ip6;
         int onlyproto = 0;
-        u16 offset = skb_network_header_len(skb);
         const struct ipv6hdr *hdr = ipv6_hdr(skb);
+        u16 offset = sizeof(*hdr);
         struct ipv6_opt_hdr *exthdr;
         const unsigned char *nh = skb_network_header(skb);
         u8 nexthdr = nh[IP6CB(skb)->nhoff];