Re: [PATCH] Input: psmouse: check the result of PSMOUSE_CMD_GET* commands

[Dmitry Torokhov <dmitry.torokhov@gmail.com>]

Hi Alexander,

On Mon, Nov 29, 2021 at 03:38:45PM +0100, Alexander Potapenko wrote:
> Execution of a PSMOUSE_CMD_GET* command may fail, leaving the output
> buffer uninitialized. Make sure to check the return value of
> ps2_command() and bail out before checking the buffer contents.
> 
> The use of uninitialized data in genius_detect() was detected by KMSAN,
> other places were fixed for the sake of uniformity.
> 
> Signed-off-by: Alexander Potapenko <glider@google.com>
> ---
>  drivers/input/mouse/psmouse-base.c | 21 ++++++++++++++++-----
>  1 file changed, 16 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/input/mouse/psmouse-base.c b/drivers/input/mouse/psmouse-base.c
> index 0b4a3039f312f..a3305653ce891 100644
> --- a/drivers/input/mouse/psmouse-base.c
> +++ b/drivers/input/mouse/psmouse-base.c
> @@ -546,13 +546,16 @@ static int genius_detect(struct psmouse *psmouse, bool set_properties)
>  {
>  	struct ps2dev *ps2dev = &psmouse->ps2dev;
>  	u8 param[4];
> +	int error;
>  
>  	param[0] = 3;
>  	ps2_command(ps2dev, param, PSMOUSE_CMD_SETRES);
>  	ps2_command(ps2dev,  NULL, PSMOUSE_CMD_SETSCALE11);
>  	ps2_command(ps2dev,  NULL, PSMOUSE_CMD_SETSCALE11);
>  	ps2_command(ps2dev,  NULL, PSMOUSE_CMD_SETSCALE11);
> -	ps2_command(ps2dev, param, PSMOUSE_CMD_GETINFO);
> +	error = ps2_command(ps2dev, param, PSMOUSE_CMD_GETINFO);
> +	if (error)
> +		return error;

If we care about this I think we should care about errors from the rest
of ps2_command()s. Otherwise we might have buffer initialized, but we
are still checking potential garbage in it.

Thanks.

-- 
Dmitry