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

The arc_uart_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.

Note that the array size is defined by a Kconfig symbol
(CONFIG_SERIAL_ARC_NR_PORTS), so this can even be triggered using a
legitimate DTB.

Fixes: ea28fd56fcde69af ("serial/arc-uart: switch to devicetree based probing")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/arc_uart.c b/drivers/tty/serial/arc_uart.c
index 2599f9e..d904a3a 100644 (file)
--- a/drivers/tty/serial/arc_uart.c
+++ b/drivers/tty/serial/arc_uart.c
@@ -593,6 +593,11 @@ static int arc_serial_probe(struct platform_device *pdev)
        if (dev_id < 0)
                dev_id = 0;
 
+       if (dev_id >= ARRAY_SIZE(arc_uart_ports)) {
+               dev_err(&pdev->dev, "serial%d out of range\n", dev_id);
+               return -EINVAL;
+       }
+
        uart = &arc_uart_ports[dev_id];
        port = &uart->port;