Re: [PATCH][next] drm/amd/display: fix potential integer overflow when shifting 32 bit variable bl_pwm

[Alex Deucher]

On Tue, Aug 18, 2020 at 8:09 AM Colin King <colin.king@xxxxxxxxxxxxx> wrote:
>
> From: Colin Ian King <colin.king@xxxxxxxxxxxxx>
>
> The 32 bit unsigned integer bl_pwm is being shifted using 32 bit arithmetic
> and then being assigned to a 64 bit unsigned integer.  There is a potential
> for a 32 bit overflow so cast bl_pwm to enforce a 64 bit shift operation
> to avoid this.
>
> Addresses-Coverity: ("unintentional integer overflow")
> Fixes: 3ba01817365c ("drm/amd/display: Move panel_cntl specific register from abm to panel_cntl.")
> Signed-off-by: Colin Ian King <colin.king@xxxxxxxxxxxxx>

Applied.  Thanks!

Alex


> ---
>  drivers/gpu/drm/amd/display/dc/dce/dce_panel_cntl.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/display/dc/dce/dce_panel_cntl.c b/drivers/gpu/drm/amd/display/dc/dce/dce_panel_cntl.c
> index a6d73d30837c..df7f826eebd8 100644
> --- a/drivers/gpu/drm/amd/display/dc/dce/dce_panel_cntl.c
> +++ b/drivers/gpu/drm/amd/display/dc/dce/dce_panel_cntl.c
> @@ -76,7 +76,7 @@ static unsigned int dce_get_16_bit_backlight_from_pwm(struct panel_cntl *panel_c
>         else
>                 bl_pwm &= 0xFFFF;
>
> -       current_backlight = bl_pwm << (1 + bl_int_count);
> +       current_backlight = (uint64_t)bl_pwm << (1 + bl_int_count);
>
>         if (bl_period == 0)
>                 bl_period = 0xFFFF;
> --
> 2.27.0
>
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