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

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Message-ID: <CADnq5_P5ozoOT4H0hrjxM1JwpvJGQ0UCnp00Kf5+Msh2CdBHgg@mail.gmail.com>
Date:   Tue, 18 Aug 2020 10:43:35 -0400
From:   Alex Deucher <alexdeucher@...il.com>
To:     Colin King <colin.king@...onical.com>
Cc:     Harry Wentland <harry.wentland@....com>,
        Leo Li <sunpeng.li@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Anthony Koo <Anthony.Koo@....com>,
        Aurabindo Pillai <aurabindo.pillai@....com>,
        amd-gfx list <amd-gfx@...ts.freedesktop.org>,
        Maling list - DRI developers 
        <dri-devel@...ts.freedesktop.org>, kernel-janitors@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH][next] drm/amd/display: fix potential integer overflow
 when shifting 32 bit variable bl_pwm

On Tue, Aug 18, 2020 at 8:09 AM Colin King <colin.king@...onical.com> wrote:
>
> From: Colin Ian King <colin.king@...onical.com>
>
> 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@...onical.com>

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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> dri-devel@...ts.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel

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