Input: usbtouchscreen - add driver_info sanity check

Add a sanity check on the device id-table driver_info field to make sure
we never access a type structure (and function pointers) outside of the
device info array (e.g. if someone fails to ifdef a device-id entry).

Note that this also suppresses a compiler warning with -Warray-bounds
(gcc-11.3.0) when compile-testing the driver without enabling any of
the device type Kconfig options:

    drivers/input/touchscreen/usbtouchscreen.c: In function 'usbtouch_probe':
    drivers/input/touchscreen/usbtouchscreen.c:1668:16:warning: array subscript <unknown> is outside array bounds of 'struct usbtouch_device_info[0]' [-Warray-bounds]
     1668 |         type = &usbtouch_dev_info[id->driver_info];

Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20220623062446.16944-1-johan@kernel.org
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

diff --git a/drivers/input/touchscreen/usbtouchscreen.c b/drivers/input/touchscreen/usbtouchscreen.c
index 43c521f..3dda6ea 100644 (file)
--- a/drivers/input/touchscreen/usbtouchscreen.c
+++ b/drivers/input/touchscreen/usbtouchscreen.c
@@ -1654,6 +1654,9 @@ static int usbtouch_probe(struct usb_interface *intf,
        if (id->driver_info == DEVTYPE_IGNORE)
                return -ENODEV;
 
+       if (id->driver_info >= ARRAY_SIZE(usbtouch_dev_info))
+               return -ENODEV;
+
        endpoint = usbtouch_get_input_endpoint(intf->cur_altsetting);
        if (!endpoint)
                return -ENXIO;