net:ipv6: check return value of pskb_trim()

goto tx_err if an unexpected result is returned by pskb_tirm()
in ip6erspan_tunnel_xmit().

Fixes: 5a963eb6 ("ip6_gre: Add ERSPAN native tunnel support")
Signed-off-by: Yuanjun Gong <ruc_gongyuanjun@163.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/ip6_gre.c

@@ -955,7 +955,8 @@ static netdev_tx_t ip6erspan_tunnel_xmit(struct sk_buff *skb,
 		goto tx_err;
 
 	if (skb->len > dev->mtu + dev->hard_header_len) {
-		pskb_trim(skb, dev->mtu + dev->hard_header_len);
+		if (pskb_trim(skb, dev->mtu + dev->hard_header_len))
+			goto tx_err;
 		truncate = true;
 	}