Re: [PATCH] drm/xe: Fix overflow in guc_ct_snapshot_capture

[Matthew Brost <matthew.brost@intel.com>]

On Wed, Mar 04, 2026 at 01:25:01PM +0200, Mika Kuoppala wrote:
> snapshot->ctb is u32*, so pointer arithmetic on it scales
> the byte offset from xe_bo_size() by 4, overshooting the
> intended start of the g2h portion and writing past the
> allocated buffer.
> 
> Fix this by using *u8 to get the arithmetic right and also
> prevent future mishaps.
> 
> Fixes: af3de6cf06f9 ("drm/xe: Split H2G and G2H into separate buffer objects")
> Cc: Matthew Brost <matthew.brost@intel.com>
> Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> Cc: "Thomas Hellström" <thomas.hellstrom@linux.intel.com>
> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> Cc: intel-xe@lists.freedesktop.org
> Signed-off-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
> ---
>  drivers/gpu/drm/xe/xe_guc_ct_types.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_guc_ct_types.h b/drivers/gpu/drm/xe/xe_guc_ct_types.h
> index 46ad1402347d..1b4b9b713d42 100644
> --- a/drivers/gpu/drm/xe/xe_guc_ct_types.h
> +++ b/drivers/gpu/drm/xe/xe_guc_ct_types.h
> @@ -74,7 +74,7 @@ struct xe_guc_ct_snapshot {
>  	/** @ctb_size: size of the snapshot of the CTB */
>  	size_t ctb_size;
>  	/** @ctb: snapshot of the entire CTB */
> -	u32 *ctb;
> +	u8 *ctb;

Ah, I see the issue. Maybe 'void *ctb'?

Matt

>  };
>  
>  /**
> -- 
> 2.43.0
>