net: erspan: remove md NULL check

The 'md' is allocated from 'tun_dst = ip_tun_rx_dst' and
since we've checked 'tun_dst', 'md' will never be NULL.
The patch removes it at both ipv4 and ipv6 erspan.

Fixes: afb4c97d90e6 ("ip6_gre: fix potential memory leak in ip6erspan_rcv")
Fixes: 50670b6ee9bc ("ip_gre: fix potential memory leak in erspan_rcv")
Cc: Haishuang Yan <yanhaishuang@cmss.chinamobile.com>
Signed-off-by: William Tu <u9012063@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/ip_gre.c

@@ -313,11 +313,6 @@ static int erspan_rcv(struct sk_buff *skb, struct tnl_ptk_info *tpi,
 				return PACKET_REJECT;
 
 			md = ip_tunnel_info_opts(&tun_dst->u.tun_info);
-			if (!md) {
-				dst_release((struct dst_entry *)tun_dst);
-				return PACKET_REJECT;
-			}
-
 			memcpy(md, pkt_md, sizeof(*md));
 			md->version = ver;
 

net/ipv6/ip6_gre.c

@@ -550,10 +550,6 @@ static int ip6erspan_rcv(struct sk_buff *skb, int gre_hdr_len,
 
 			info = &tun_dst->u.tun_info;
 			md = ip_tunnel_info_opts(info);
-			if (!md) {
-				dst_release((struct dst_entry *)tun_dst);
-				return PACKET_REJECT;
-			}
 
 			memcpy(md, pkt_md, sizeof(*md));
 			md->version = ver;