net: caif: Add a missing rcu_read_unlock() in caif_flow_cb

Add a missing rcu_read_unlock in the error path

Fixes: c95567c8 ("caif: added check for potential null return")
Signed-off-by: NYueHaibing <yuehaibing@huawei.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/caif/caif_dev.c

@@ -131,8 +131,10 @@ static void caif_flow_cb(struct sk_buff *skb)
 	caifd = caif_get(skb->dev);
 
 	WARN_ON(caifd == NULL);
-	if (caifd == NULL)
+	if (!caifd) {
+		rcu_read_unlock();
 		return;
+	}
 
 	caifd_hold(caifd);
 	rcu_read_unlock();