When __ip6_tnl_rcv fails, the tun_dst won't be freed, so call
dst_release to free it in error code path.
Fixes: 8d79266bc48c ("ip6_tunnel: add collect_md mode to IPv6 tunnels")
CC: Alexei Starovoitov <ast@fb.com>
Tested-by: Zhang Shengju <zhangshengju@cmss.chinamobile.com>
Signed-off-by: Haishuang Yan <yanhaishuang@cmss.chinamobile.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
        return 0;
 
 drop:
+       if (tun_dst)
+               dst_release((struct dst_entry *)tun_dst);
        kfree_skb(skb);
        return 0;
 }