Re: [v5 09/14] drm/i915/color: Add support for 1D LUT in SDR planes

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:

Pre-existing issues:
- [High] This problem wasn't introduced by this patch, but if colorop initialization fails early, the cleanup path calls `intel_colorop_destroy()` on a partially initialized object, leading to a NULL pointer dereference and uninitialized list head usage.
- [High] This problem wasn't introduced by this patch, but an unchecked return value from `kasprintf()` leads to a NULL pointer dereference when creating the color pipeline property.
--

--- Patch [9]: [v5 09/14] drm/i915/color: Add support for 1D LUT in SDR planes ---
commit e6938001b7cb4179a20fa4b4c3bd94fef8282c50
Author: Chaitanya Kumar Borah <chaitanya.kumar.borah@intel.com>

drm/i915/color: Add support for 1D LUT in SDR planes

Extend the SDR plane color pipeline to include pre- and post-CSC 1D LUT blocks.
SDR planes use a smaller LUT size than HDR planes and therefore initialize the
1D LUT colorops with the appropriate hardware capacity.

> diff --git a/drivers/gpu/drm/i915/display/intel_color_pipeline.c b/drivers/gpu/drm/i915/display/intel_color_pipeline.c
> index 7457fa51cb97a..136b9378ca484 100644
> --- a/drivers/gpu/drm/i915/display/intel_color_pipeline.c
> +++ b/drivers/gpu/drm/i915/display/intel_color_pipeline.c

[ ... ]

> @@ -81,7 +86,9 @@ struct intel_colorop *intel_color_pipeline_plane_add_colorop(struct drm_plane *p
>  		ret = drm_plane_colorop_curve_1d_lut_init(dev,
>  							  &colorop->base, plane,
>  							  &intel_colorop_funcs,
> -							  PLANE_DEGAMMA_SIZE,
> +							  is_hdr ?
> +							  PLANE_DEGAMMA_SIZE :
> +							  PLANE_DEGAMMA_SIZE_SDR,
>  							  DRM_COLOROP_LUT1D_INTERPOLATION_LINEAR,
>  							  DRM_COLOROP_FLAG_ALLOW_BYPASS);
>  		break;

[Severity: High]
This isn't a bug introduced by this patch, but if colorop initialization fails
early, the cleanup path calls intel_colorop_destroy() on a partially
initialized object. Could this lead to a NULL pointer dereference and
uninitialized list head usage?

If drm_plane_colorop_init() fails early (e.g., drm_mode_object_add() returns
-ENOMEM), colorop->dev remains NULL and colorop->head is zero-filled. The error
path jumps to cleanup and invokes intel_colorop_destroy(), which delegates to
drm_colorop_cleanup():

drivers/gpu/drm/drm_colorop.c:drm_colorop_cleanup() {
    struct drm_mode_config *config = &dev->mode_config;

    list_del(&colorop->head);
    config->num_colorop--;
}

This unconditionally dereferences dev (which is NULL) and calls list_del() on a
zero-filled list head.

[Severity: High]
This is also a pre-existing issue in the same file, but an unchecked return
value from kasprintf() can lead to a NULL pointer dereference when creating the
color pipeline property.

In _intel_color_pipeline_plane_init(), kasprintf() allocates memory for
list->name:

drivers/gpu/drm/i915/display/intel_color_pipeline.c:_intel_color_pipeline_plane_init() {
    ...
    list->name = kasprintf(GFP_KERNEL, "Color Pipeline %d", colorop[0]->base.base.id);

    return 0;
}

If kasprintf() fails, it returns NULL, and the function unconditionally returns
success. This NULL name is later passed to drm_property_add_enum(), where a
strlen(name) call will crash the kernel:

drivers/gpu/drm/drm_property.c:drm_property_add_enum() {
    ...
    if (WARN_ON(strlen(name) >= DRM_PROP_NAME_LEN))
        return 0;
    ...
}

Should the return value of kasprintf() be checked and handled as an error here?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260720045131.971650-1-chaitanya.kumar.borah@intel.com?part=9