serial: fsl_lpuart: Fix out-of-bounds access through DT alias

The lpuart_ports[] array is indexed using a value derived from the
"serialN" alias in DT, which may lead to an out-of-bounds access.

Fix this by adding a range check.

Fixes: c9e2e946 ("tty: serial: add Freescale lpuart driver support")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/fsl_lpuart.c

@@ -2145,6 +2145,10 @@ static int lpuart_probe(struct platform_device *pdev)
 		dev_err(&pdev->dev, "failed to get alias id, errno %d\n", ret);
 		return ret;
 	}
+	if (ret >= ARRAY_SIZE(lpuart_ports)) {
+		dev_err(&pdev->dev, "serial%d out of range\n", ret);
+		return -EINVAL;
+	}
 	sport->port.line = ret;
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	sport->port.membase = devm_ioremap_resource(&pdev->dev, res);