[PATCH] drm/msm/dpu: Cast an operand to u64 to prevent potential overflow in _dpu_core_perf_calc_clk()

[Abhinav Kumar]

On 10/29/2024 9:26 AM, Gax-c wrote:
> From: Zichen Xie <zichenxie0106 at gmail.com>
> 
> There may be a potential integer overflow issue in
> _dpu_core_perf_calc_clk(). crtc_clk is defined as u64, while
> mode->vtotal, mode->hdisplay, and drm_mode_vrefresh(mode) are defined as
> a smaller data type. The result of the calculation will be limited to
> "int" in this case without correct casting. In screen with high
> resolution and high refresh rate, integer overflow may happen.
> So, we recommend adding an extra cast to prevent potential
> integer overflow.
> 

You could just say "cast crtc_clk calculation to u64 in 
_dpu_core_perf_calc_clk()" in the subject to be more specific about 
which operand you are referring to.


> Fixes: c33b7c0389e1 ("drm/msm/dpu: add support for clk and bw scaling for display")
> Signed-off-by: Zichen Xie <zichenxie0106 at gmail.com>
> ---
>   drivers/gpu/drm/msm/disp/dpu1/dpu_core_perf.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_core_perf.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_core_perf.c
> index 68fae048a9a8..260accc151d4 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_core_perf.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_core_perf.c
> @@ -80,7 +80,7 @@ static u64 _dpu_core_perf_calc_clk(const struct dpu_perf_cfg *perf_cfg,
>   
>   	mode = &state->adjusted_mode;
>   
> -	crtc_clk = mode->vtotal * mode->hdisplay * drm_mode_vrefresh(mode);
> +	crtc_clk = (u64)mode->vtotal * mode->hdisplay * drm_mode_vrefresh(mode);
>   
>   	drm_atomic_crtc_for_each_plane(plane, crtc) {
>   		pstate = to_dpu_plane_state(plane->state);

Change looks valid to me, so with the subject fixed a bit:

Reviewed-by: Abhinav Kumar <quic_abhinavk at quicinc.com>