net: dsa: add error handling for pskb_trim_rcsum

[ Upstream commit 349b71d6 ]

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

net/dsa/tag_trailer.c

@@ -79,7 +79,8 @@ static struct sk_buff *trailer_rcv(struct sk_buff *skb, struct net_device *dev,
 	if (unlikely(ds->cpu_port_mask & BIT(source_port)))
 		return NULL;
 
-	pskb_trim_rcsum(skb, skb->len - 4);
+	if (pskb_trim_rcsum(skb, skb->len - 4))
+		return NULL;
 
 	skb->dev = ds->ports[source_port].netdev;