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

BugLink: https://bugs.launchpad.net/bugs/1775771

[ Upstream commit ffab87fd ]

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: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

drivers/tty/serial/fsl_lpuart.c

@@ -1818,6 +1818,10 @@ 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;
 	sport->lpuart32 = of_device_is_compatible(np, "fsl,ls1021a-lpuart");