ipv4 tunnels: fix an oops when using ipip/sit with IPsec

Since commit 3d7b46cd20e3 (ip_tunnel: push generic protocol handling to
ip_tunnel module.), an Oops is triggered when an xfrm policy is configured on
an IPv4 over IPv4 tunnel.

xfrm4_policy_check() calls __xfrm_policy_check2(), which uses skb_dst(skb). But
this field is NULL because iptunnel_pull_header() calls skb_dst_drop(skb).

Signed-off-by: Li Hongjun <hongjun.li@6wind.com>
Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 3 deletions

diff --git a/net/ipv4/ipip.c b/net/ipv4/ipip.c
index 51fc2a1dcdd3..b3ac3c3f6219 100644
--- a/net/ipv4/ipip.c
+++ b/net/ipv4/ipip.c
@@ -190,15 +190,14 @@ static int ipip_rcv(struct sk_buff *skb)
         struct ip_tunnel *tunnel;
         const struct iphdr *iph;
 
-        if (iptunnel_pull_header(skb, 0, tpi.proto))
-                goto drop;
-
         iph = ip_hdr(skb);
         tunnel = ip_tunnel_lookup(itn, skb->dev->ifindex, TUNNEL_NO_KEY,
                         iph->saddr, iph->daddr, 0);
         if (tunnel) {
                 if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb))
                         goto drop;
+                if (iptunnel_pull_header(skb, 0, tpi.proto))
+                        goto drop;
                 return ip_tunnel_rcv(tunnel, skb, &tpi, log_ecn_error);
         }