Re: [Intel-gfx] [PATCH] drm/i915/bios: fix slab-out-of-bounds access

["Thomas Hellström" <thomas.hellstrom@linux.intel.com>]

On 12/21/21 14:08, Jani Nikula wrote:
> If VBT size is not a multiple of 4, the last 4-byte store will be out of
> bounds of the allocated buffer. Spotted with KASAN. Round up the
> allocation size.
>
> Reported-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> Fixes: a36e7dc0af1c ("drm/i915/dg1: Read OPROM via SPI controller")
> Cc: Clint Taylor <clinton.a.taylor@intel.com>
> Cc: Lucas De Marchi <lucas.demarchi@intel.com>
> Signed-off-by: Jani Nikula <jani.nikula@intel.com>


> ---
>   drivers/gpu/drm/i915/display/intel_bios.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_bios.c b/drivers/gpu/drm/i915/display/intel_bios.c
> index 76a8f001f4c4..310609d186cd 100644
> --- a/drivers/gpu/drm/i915/display/intel_bios.c
> +++ b/drivers/gpu/drm/i915/display/intel_bios.c
> @@ -2369,7 +2369,7 @@ static struct vbt_header *spi_oprom_get_vbt(struct drm_i915_private *i915)
>   	vbt_size = intel_uncore_read(&i915->uncore, PRIMARY_SPI_TRIGGER);
>   	vbt_size &= 0xffff;
>   
> -	vbt = kzalloc(vbt_size, GFP_KERNEL);
> +	vbt = kzalloc(roundup(vbt_size, 4), GFP_KERNEL);

Use round_up since a power of 2?

Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>

>   	if (!vbt)
>   		goto err_not_found;
>