fsl/fman: fix dereference null return value

Check before using returned value to avoid dereferencing null pointer.

Fixes: 18a6c85f ("fsl/fman: Add FMan Port Support")
Signed-off-by: Florinel Iordache <florinel.iordache@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/freescale/fman/fman_port.c

@@ -1767,6 +1767,7 @@ static int fman_port_probe(struct platform_device *of_dev)
 	struct fman_port *port;
 	struct fman *fman;
 	struct device_node *fm_node, *port_node;
+	struct platform_device *fm_pdev;
 	struct resource res;
 	struct resource *dev_res;
 	u32 val;
@@ -1791,8 +1792,14 @@ static int fman_port_probe(struct platform_device *of_dev)
 		goto return_err;
 	}
 
-	fman = dev_get_drvdata(&of_find_device_by_node(fm_node)->dev);
+	fm_pdev = of_find_device_by_node(fm_node);
 	of_node_put(fm_node);
+	if (!fm_pdev) {
+		err = -EINVAL;
+		goto return_err;
+	}
+
+	fman = dev_get_drvdata(&fm_pdev->dev);
 	if (!fman) {
 		err = -EINVAL;
 		goto return_err;