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

The sirf_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: a6ffe896 ("serial: sirf: use dynamic method allocate uart structure")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/sirfsoc_uart.c

@@ -1283,6 +1283,11 @@ static int sirfsoc_uart_probe(struct platform_device *pdev)
 		goto err;
 	}
 	sirfport->port.line = of_alias_get_id(np, "serial");
+	if (sirfport->port.line >= ARRAY_SIZE(sirf_ports)) {
+		dev_err(&pdev->dev, "serial%d out of range\n",
+			sirfport->port.line);
+		return -EINVAL;
+	}
 	sirf_ports[sirfport->port.line] = sirfport;
 	sirfport->port.iotype = UPIO_MEM;
 	sirfport->port.flags = UPF_BOOT_AUTOCONF;