net: microchip: sparx5: Fix potential null-ptr-deref in sparx_stats_init() and sparx5_start()

sparx_stats_init() calls create_singlethread_workqueue() and not
checked the ret value, which may return NULL. And a null-ptr-deref may
happen:

sparx_stats_init()
    create_singlethread_workqueue() # failed, sparx5->stats_queue is NULL
    queue_delayed_work()
        queue_delayed_work_on()
            __queue_delayed_work()  # warning here, but continue
                __queue_work()      # access wq->flags, null-ptr-deref

Check the ret value and return -ENOMEM if it is NULL. So as
sparx5_start().

Fixes: af4b1102 ("net: sparx5: add ethtool configuration and statistics support")
Fixes: b37a1bae ("net: sparx5: add mactable support")
Signed-off-by: Shang XiaoJing <shangxiaojing@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/microchip/sparx5/sparx5_ethtool.c

@@ -1253,6 +1253,9 @@ int sparx_stats_init(struct sparx5 *sparx5)
 	snprintf(queue_name, sizeof(queue_name), "%s-stats",
 		 dev_name(sparx5->dev));
 	sparx5->stats_queue = create_singlethread_workqueue(queue_name);
+	if (!sparx5->stats_queue)
+		return -ENOMEM;
+
 	INIT_DELAYED_WORK(&sparx5->stats_work, sparx5_check_stats_work);
 	queue_delayed_work(sparx5->stats_queue, &sparx5->stats_work,
 			   SPX5_STATS_CHECK_DELAY);

drivers/net/ethernet/microchip/sparx5/sparx5_main.c

@@ -659,6 +659,9 @@ static int sparx5_start(struct sparx5 *sparx5)
 	snprintf(queue_name, sizeof(queue_name), "%s-mact",
 		 dev_name(sparx5->dev));
 	sparx5->mact_queue = create_singlethread_workqueue(queue_name);
+	if (!sparx5->mact_queue)
+		return -ENOMEM;
+
 	INIT_DELAYED_WORK(&sparx5->mact_work, sparx5_mact_pull_work);
 	queue_delayed_work(sparx5->mact_queue, &sparx5->mact_work,
 			   SPX5_MACT_PULL_DELAY);