Re: [PATCH v2 2/7] drm/panfrost: Prevent division by 0

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:

Pre-existing issues:
- [High] The exact same division-by-zero vulnerability fixed in panfrost_devfreq.c is present in the Lima, Panthor, and Nouveau (gk20a) drivers.
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commit dc73067c1030f65e3609c76a060b1b1176f85e4e
Author: Adrián Larumbe <adrian.larumbe@collabora.com>

drm/panfrost: Prevent division by 0

This commit clamps the devfreq total_time to 0 when it is less than 100ns
in panfrost_devfreq_get_dev_status() to prevent a division by zero error
during debug printing.

Closes: https://gitlab.freedesktop.org/panfrost/linux/-/work_items/88

> diff --git a/drivers/gpu/drm/panfrost/panfrost_devfreq.c b/drivers/gpu/drm/panfrost/panfrost_devfreq.c
> index b51c307788110..e34de47bf43bb 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_devfreq.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_devfreq.c
> @@ -78,7 +78,8 @@ static int panfrost_devfreq_get_dev_status(struct device *dev,
>  
>  	dev_dbg(pfdev->base.dev, "busy %lu total %lu %lu %% freq %lu MHz\n",
>  		status->busy_time, status->total_time,
> -		status->busy_time / (status->total_time / 100),
> +		status->total_time >= 100 ?
> +			status->busy_time / (status->total_time / 100) : 0,

[Severity: High]
This is a pre-existing issue, but the exact same division-by-zero vulnerability
fixed here is also present in other DRM drivers.

In drivers/gpu/drm/lima/lima_devfreq.c:lima_devfreq_get_dev_status():
    status->busy_time / (status->total_time / 100),

In drivers/gpu/drm/panthor/panthor_devfreq.c:panthor_devfreq_get_dev_status():
    status->busy_time / (status->total_time / 100),

In drivers/gpu/drm/nouveau/nvkm/subdev/clk/gk20a_devfreq.c:gk20a_devfreq_get_dev_status():
    status->busy_time / (status->total_time / 100),

If userspace repeatedly reads the devfreq load in quick succession, total_time
can be less than 100ns, leading to a division-by-zero kernel panic when debug
printing is enabled.

Should these other drivers be patched similarly?

>  		status->current_frequency / 1000 / 1000);
>  
>  	return 0;
>  }

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Sashiko AI review · https://sashiko.dev/#/patchset/20260604-claude-fixes-v2-0-57c6bd4c1655@collabora.com?part=2