sit: Add missing kfree_skb() on pskb_may_pull() failure.

Noticed by Paul Marks <paul@pmarks.net>.

Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/sit.c b/net/ipv6/sit.c
index 4b2f103..5a6fab9 100644
--- a/net/ipv6/sit.c
+++ b/net/ipv6/sit.c
@@ -596,9 +596,9 @@
 	}
 
 	icmp_send(skb, ICMP_DEST_UNREACH, ICMP_PORT_UNREACH, 0);
-	kfree_skb(skb);
 	read_unlock(&ipip6_lock);
 out:
+	kfree_skb(skb);
 	return 0;
 }