Re: [PATCH] HID: input: set usage type to key on keycode remap

[Dmitry Torokhov]

On Thu, Oct 28, 2021 at 10:55:42PM +0200, Thomas Weißschuh wrote:
> When a scancode is manually remapped that previously was not handled as
> key, then the old usage type was incorrectly reused.
> 
> This caused issues on a "04b3:301b IBM Corp. SK-8815 Keyboard" which has
> marked some of its keys with an invalid HID usage.  These invalid usage
> keys are being ignored since support for USB programmable buttons was
> added.
> 
> The scancodes are however remapped explicitly by the systemd hwdb to the
> keycodes that are printed on the physical buttons.  During this mapping
> step the existing usage is retrieved which will be found with a default
> type of 0 (EV_SYN) instead of EV_KEY.
> 
> The events with the correct code but EV_SYN type are not forwarded to
> userspace.
> 
> This also leads to a kernel oops when trying to print the report descriptor
> via debugfs.  hid_resolv_event() tries to resolve a EV_SYN event with an
> EV_KEY code which leads to an out-of-bounds access in the EV_SYN names
> array.
> 
> Fixes: bcfa8d1457 ("HID: input: Add support for Programmable Buttons")
> Fixes: f5854fad39 ("Input: hid-input - allow mapping unknown usages")
> Reported-by: Brent Roman <brent@xxxxxxxxx>
> Tested-by: Brent Roman <brent@xxxxxxxxx>
> Signed-off-by: Thomas Weißschuh <linux@xxxxxxxxxxxxxx>

Makes sense.

Reviewed-by: Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx>

> ---
>  drivers/hid/hid-input.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/hid/hid-input.c b/drivers/hid/hid-input.c
> index 4b5ebeacd283..21d8cc64064d 100644
> --- a/drivers/hid/hid-input.c
> +++ b/drivers/hid/hid-input.c
> @@ -160,6 +160,7 @@ static int hidinput_setkeycode(struct input_dev *dev,
>  	if (usage) {
>  		*old_keycode = usage->type == EV_KEY ?
>  				usage->code : KEY_RESERVED;
> +		usage->type = EV_KEY;
>  		usage->code = ke->keycode;
>  
>  		clear_bit(*old_keycode, dev->keybit);
> 
> base-commit: 42d43c92fc577dca59ed74aec7868abec8d6ca6e
> -- 
> 2.33.1
> 

Thanks.

-- 
Dmitry