Re: [PATCH] drm/i915/bios: range check LFP Data Block panel_type2

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Thu, Jun 25, 2026 at 04:51:30PM +0300, Jani Nikula wrote:
> While the panel_type from LFP Data Block is range checked, panel_type2
> is not. Add a few helpers for range checking, and use them to not only
> check panel_type2, but also imrove clarity and correctness in the panel
> type selection.
> 
> Discovered using AI-assisted static analysis confirmed by Intel Product
> Security.
> 
> Reported-by: Martin Hodo <martin.hodo@intel.com>
> Fixes: 6434cf630086 ("drm/i915/bios: calculate panel type as per child device index in VBT")
> Cc: <stable@vger.kernel.org> # v6.0+
> Cc: Animesh Manna <animesh.manna@intel.com>
> Cc: Ville Syrjälä <ville.syrjala@intel.com>
> Signed-off-by: Jani Nikula <jani.nikula@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_bios.c | 29 +++++++++++++++++------
>  1 file changed, 22 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_bios.c b/drivers/gpu/drm/i915/display/intel_bios.c
> index 15ebadc72b88..0c420019e46a 100644
> --- a/drivers/gpu/drm/i915/display/intel_bios.c
> +++ b/drivers/gpu/drm/i915/display/intel_bios.c
> @@ -623,6 +623,16 @@ get_lfp_data_tail(const struct bdb_lfp_data *data,
>  		return NULL;
>  }
>  
> +static bool is_panel_type_valid(int panel_type)
> +{
> +	return panel_type >= 0 && panel_type < 16;
> +}
> +
> +static bool is_panel_type_valid_or_pnp(int panel_type)
> +{
> +	return is_panel_type_valid(panel_type) || panel_type == 0xff;
> +}
> +
>  static int opregion_get_panel_type(struct intel_display *display,
>  				   const struct intel_bios_encoder_data *devdata,
>  				   const struct drm_edid *drm_edid, bool use_fallback)
> @@ -640,15 +650,21 @@ static int vbt_get_panel_type(struct intel_display *display,
>  	if (!lfp_options)
>  		return -1;
>  
> -	if (lfp_options->panel_type > 0xf &&
> -	    lfp_options->panel_type != 0xff) {
> +	if (!is_panel_type_valid_or_pnp(lfp_options->panel_type)) {
>  		drm_dbg_kms(display->drm, "Invalid VBT panel type 0x%x\n",
>  			    lfp_options->panel_type);
>  		return -1;
>  	}
>  
> -	if (devdata && devdata->child.handle == DEVICE_HANDLE_LFP2)
> +	if (devdata && devdata->child.handle == DEVICE_HANDLE_LFP2) {
> +		if (!is_panel_type_valid_or_pnp(lfp_options->panel_type2)) {
> +			drm_dbg_kms(display->drm, "Invalid VBT panel type 2 0x%x\n",
> +				    lfp_options->panel_type2);
> +			return -1;
> +		}
> +
>  		return lfp_options->panel_type2;
> +	}
>  
>  	drm_WARN_ON(display->drm,
>  		    devdata && devdata->child.handle != DEVICE_HANDLE_LFP1);
> @@ -762,13 +778,12 @@ static int get_panel_type(struct intel_display *display,
>  				    panel_types[i].name, panel_types[i].panel_type);
>  	}
>  
> -	if (panel_types[PANEL_TYPE_OPREGION].panel_type >= 0)
> +	if (is_panel_type_valid(panel_types[PANEL_TYPE_OPREGION].panel_type))
>  		i = PANEL_TYPE_OPREGION;
>  	else if (panel_types[PANEL_TYPE_VBT].panel_type == 0xff &&

is_panel_type_pnp()?

> -		 panel_types[PANEL_TYPE_PNPID].panel_type >= 0)
> +		 is_panel_type_valid(panel_types[PANEL_TYPE_PNPID].panel_type))
>  		i = PANEL_TYPE_PNPID;
> -	else if (panel_types[PANEL_TYPE_VBT].panel_type != 0xff &&
> -		 panel_types[PANEL_TYPE_VBT].panel_type >= 0)
> +	else if (is_panel_type_valid(panel_types[PANEL_TYPE_VBT].panel_type))
>  		i = PANEL_TYPE_VBT;
>  	else
>  		i = PANEL_TYPE_FALLBACK;
> -- 
> 2.47.3

-- 
Ville Syrjälä
Intel