[Intel-gfx] [PATCH 08/15] drm/i915/dsi: be defensive about out of bounds operation byte

[Daniel Vetter]

On Mon, Dec 21, 2015 at 03:10:59PM +0200, Jani Nikula wrote:
> Untie the VBT based generic panel driver from the VBT parsing, so that
> the two don't have to be updated in lockstep.
> 
> Signed-off-by: Jani Nikula <jani.nikula at intel.com>
> ---
>  drivers/gpu/drm/i915/intel_dsi_panel_vbt.c | 22 +++++++++-------------
>  1 file changed, 9 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dsi_panel_vbt.c b/drivers/gpu/drm/i915/intel_dsi_panel_vbt.c
> index 45512e0df57a..ba5355506590 100644
> --- a/drivers/gpu/drm/i915/intel_dsi_panel_vbt.c
> +++ b/drivers/gpu/drm/i915/intel_dsi_panel_vbt.c
> @@ -232,11 +232,9 @@ static const u8 *mipi_exec_gpio(struct intel_dsi *intel_dsi, const u8 *data)
>  typedef const u8 * (*fn_mipi_elem_exec)(struct intel_dsi *intel_dsi,
>  					const u8 *data);
>  static const fn_mipi_elem_exec exec_elem[] = {
> -	NULL, /* reserved */
> -	mipi_exec_send_packet,
> -	mipi_exec_delay,
> -	mipi_exec_gpio,
> -	NULL, /* status read; later */
> +	[MIPI_SEQ_ELEM_SEND_PKT] = mipi_exec_send_packet,
> +	[MIPI_SEQ_ELEM_DELAY] = mipi_exec_delay,
> +	[MIPI_SEQ_ELEM_GPIO] = mipi_exec_gpio,
>  };
>  
>  /*
> @@ -264,7 +262,6 @@ static const char *sequence_name(enum mipi_seq seq_id)
>  static void generic_exec_sequence(struct intel_dsi *intel_dsi, const u8 *data)
>  {
>  	fn_mipi_elem_exec mipi_elem_exec;
> -	int index;
>  
>  	if (!data)
>  		return;
> @@ -277,15 +274,14 @@ static void generic_exec_sequence(struct intel_dsi *intel_dsi, const u8 *data)
>  
>  	/* parse each byte till we reach end of sequence byte - 0x00 */
>  	while (1) {
> -		index = *data;
> -		mipi_elem_exec = exec_elem[index];
> -		if (!mipi_elem_exec) {
> -			DRM_ERROR("Unsupported MIPI element, skipping sequence execution\n");
> +		u8 operation_byte = *data++;
> +		if (operation_byte >= ARRAY_SIZE(exec_elem) ||
> +		    !exec_elem[operation_byte]) {
> +			DRM_ERROR("Unsupported MIPI operation byte %u\n",

Maybe DRM_ERROR in the previous patch too? Just for ocd consistency.

Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch>

> +				  operation_byte);
>  			return;
>  		}
> -
> -		/* goto element payload */
> -		data++;
> +		mipi_elem_exec = exec_elem[operation_byte];
>  
>  		/* execute the element specific rotines */
>  		data = mipi_elem_exec(intel_dsi, data);
> -- 
> 2.1.4
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch