net: moxa: fix UAF in moxart_mac_probe

commit c78eaee upstream.

In case of netdev registration failure the code path will
jump to init_fail label:

init_fail:
	netdev_err(ndev, "init failed\n");
	moxart_mac_free_memory(ndev);
irq_map_fail:
	free_netdev(ndev);
	return ret;

So, there is no need to call free_netdev() before jumping
to error handling path, since it can cause UAF or double-free
bug.

Fixes: 6c821bd ("net: Add MOXA ART SoCs ethernet driver")
Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/net/ethernet/moxa/moxart_ether.c

@@ -541,10 +541,8 @@ static int moxart_mac_probe(struct platform_device *pdev)
 	SET_NETDEV_DEV(ndev, &pdev->dev);
 
 	ret = register_netdev(ndev);
-	if (ret) {
-		free_netdev(ndev);
+	if (ret)
 		goto init_fail;
-	}
 
 	netdev_dbg(ndev, "%s: IRQ=%d address=%pM\n",
 		   __func__, ndev->irq, ndev->dev_addr);