Re: [PATCH 05/15] drm/i915/bios: abstract finding the panel sequence block

[Daniel Vetter <daniel@ffwll.ch>]

On Mon, Dec 21, 2015 at 03:10:56PM +0200, Jani Nikula wrote:
> Make the whole thing easier to read.
> 
> Signed-off-by: Jani Nikula <jani.nikula@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_bios.c | 76 +++++++++++++++++++++------------------
>  1 file changed, 42 insertions(+), 34 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_bios.c b/drivers/gpu/drm/i915/intel_bios.c
> index 7393596df37d..9511a5341562 100644
> --- a/drivers/gpu/drm/i915/intel_bios.c
> +++ b/drivers/gpu/drm/i915/intel_bios.c
> @@ -697,7 +697,7 @@ parse_psr(struct drm_i915_private *dev_priv, const struct bdb_header *bdb)
>  	dev_priv->vbt.psr.tp2_tp3_wakeup_time = psr_table->tp2_tp3_wakeup_time;
>  }
>  
> -static u8 *goto_next_sequence(u8 *data, int *size)
> +static u8 *goto_next_sequence(u8 *data, u16 *size)
>  {
>  	u16 len;
>  	int tmp = *size;
> @@ -818,15 +818,52 @@ parse_mipi_config(struct drm_i915_private *dev_priv,
>  	dev_priv->vbt.dsi.panel_id = MIPI_DSI_GENERIC_PANEL_ID;
>  }
>  
> +/* Find the sequence block and size for the given panel. */
> +static const u8 *
> +find_panel_sequence_block(const struct bdb_mipi_sequence *sequence,
> +			  u16 panel_id, u16 *seq_size)
> +{
> +	u32 total = get_blocksize(sequence);
> +	const u8 *data = &sequence->data[0];
> +	u8 current_id;
> +	u16 current_size;
> +	int index = 0;
> +	int i;
> +
> +	for (i = 0; i < MAX_MIPI_CONFIGURATIONS && index + 3 < total; i++) {

Commit message should mention that you make the parsin more robust and
ensure we don't walk over the end of the allocated buffer.

> +		current_id = *(data + index);
> +		index++;
> +
> +		current_size = *((const u16 *)(data + index));
> +		index += 2;
> +
> +		if (index + current_size > total) {
> +			DRM_ERROR("Invalid sequence block\n");
> +			return NULL;
> +		}
> +
> +		if (current_id == panel_id) {
> +			*seq_size = current_size;
> +			return data + index;
> +		}
> +
> +		index += current_size;
> +	}
> +
> +	DRM_ERROR("Sequence block detected but no valid configuration\n");
> +
> +	return NULL;
> +}
> +
>  static void
>  parse_mipi_sequence(struct drm_i915_private *dev_priv,
>  		    const struct bdb_header *bdb)
>  {
>  	const struct bdb_mipi_sequence *sequence;
>  	const u8 *seq_data;
> +	u16 seq_size;
>  	u8 *data;
>  	u16 block_size;
> -	int i, panel_id, seq_size;
>  
>  	/* Only our generic panel driver uses the sequence block. */
>  	if (dev_priv->vbt.dsi.panel_id != MIPI_DSI_GENERIC_PANEL_ID)
> @@ -853,40 +890,11 @@ parse_mipi_sequence(struct drm_i915_private *dev_priv,
>  	 */
>  	dev_priv->vbt.dsi.seq_version = sequence->version;
>  
> -	seq_data = &sequence->data[0];
> -
> -	/*
> -	 * sequence block is variable length and hence we need to parse and
> -	 * get the sequence data for specific panel id
> -	 */
> -	for (i = 0; i < MAX_MIPI_CONFIGURATIONS; i++) {
> -		panel_id = *seq_data;
> -		seq_size = *((u16 *) (seq_data + 1));
> -		if (panel_id == panel_type)
> -			break;
> -
> -		/* skip the sequence including seq header of 3 bytes */
> -		seq_data = seq_data + 3 + seq_size;
> -		if ((seq_data - &sequence->data[0]) > block_size) {
> -			DRM_ERROR("Sequence start is beyond sequence block size, corrupted sequence block\n");
> -			return;
> -		}
> -	}
> -
> -	if (i == MAX_MIPI_CONFIGURATIONS) {
> -		DRM_ERROR("Sequence block detected but no valid configuration\n");
> +	seq_data = find_panel_sequence_block(sequence, panel_type, &seq_size);
> +	if (!seq_data)
>  		return;
> -	}
> -
> -	/* check if found sequence is completely within the sequence block
> -	 * just being paranoid */
> -	if (seq_size > block_size) {
> -		DRM_ERROR("Corrupted sequence/size, bailing out\n");
> -		return;
> -	}
>  
> -	/* skip the panel id(1 byte) and seq size(2 bytes) */
> -	dev_priv->vbt.dsi.data = kmemdup(seq_data + 3, seq_size, GFP_KERNEL);
> +	dev_priv->vbt.dsi.data = kmemdup(seq_data, seq_size, GFP_KERNEL);

Should dropping the +3 be in a separate patch?

Otherwise looks good, with the above 2 addressed

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

>  	if (!dev_priv->vbt.dsi.data)
>  		return;
>  
> -- 
> 2.1.4
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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