net: dsa: add error handling for pskb_trim_rcsum

When pskb_trim_rcsum fails, the lack of error-handling code may
cause unexpected results.

This patch adds error-handling code after calling pskb_trim_rcsum.
Signed-off-by: Zhouyang Jia <jiazhouyang09@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/dsa/tag_trailer.c

@@ -75,7 +75,8 @@ static struct sk_buff *trailer_rcv(struct sk_buff *skb, struct net_device *dev,
 	if (!skb->dev)
 		return NULL;
 
-	pskb_trim_rcsum(skb, skb->len - 4);
+	if (pskb_trim_rcsum(skb, skb->len - 4))
+		return NULL;
 
 	return skb;
 }