net: erspan: fix wrong return value

If pskb_may_pull return failed, return PACKET_REJECT
instead of -ENOMEM.

Fixes: 94d7d8f2 ("ip6_gre: add erspan v2 support")
Fixes: f551c91d ("net: erspan: introduce erspan v2 for ip_gre")
Signed-off-by: William Tu <u9012063@gmail.com>
Cc: Haishuang Yan <yanhaishuang@cmss.chinamobile.com>
Acked-by: Haishuang Yan <yanhaishuang@cmss.chinamobile.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/ip_gre.c

@@ -287,7 +287,7 @@ static int erspan_rcv(struct sk_buff *skb, struct tnl_ptk_info *tpi,
 	if (tunnel) {
 		len = gre_hdr_len + erspan_hdr_len(ver);
 		if (unlikely(!pskb_may_pull(skb, len)))
-			return -ENOMEM;
+			return PACKET_REJECT;
 
 		if (__iptunnel_pull_header(skb,
 					   len,

net/ipv6/ip6_gre.c

@@ -524,7 +524,7 @@ static int ip6erspan_rcv(struct sk_buff *skb, int gre_hdr_len,
 		int len = erspan_hdr_len(ver);
 
 		if (unlikely(!pskb_may_pull(skb, len)))
-			return -ENOMEM;
+			return PACKET_REJECT;
 
 		if (__iptunnel_pull_header(skb, len,
 					   htons(ETH_P_TEB),