Re: [PATCH] drm/xe/rtp: Fix out-of-bounds array access

[Rodrigo Vivi <rodrigo.vivi@intel.com>]

On Fri, Jun 28, 2024 at 09:17:26AM -0700, Lucas De Marchi wrote:
> Increment the counter before checking for number of rules, otherwise
> when there's no XE_RTP_MATCH_OR an out-of-bounds access is done, as
> reported by kasan:
> 
> 	BUG: KASAN: global-out-of-bounds in rule_matches+0xb6d/0x11c0 [xe]
> 	Read of size 1 at addr ffffffffa0a50b70 by task systemd-udevd/243

Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

> 
> Fixes: dc72c52a42e0 ("drm/xe/rtp: Allow to OR rules")
> Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
> Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
> ---
>  drivers/gpu/drm/xe/xe_rtp.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_rtp.c b/drivers/gpu/drm/xe/xe_rtp.c
> index 5b27f7c45ea3..02e28274282f 100644
> --- a/drivers/gpu/drm/xe/xe_rtp.c
> +++ b/drivers/gpu/drm/xe/xe_rtp.c
> @@ -121,7 +121,7 @@ static bool rule_matches(const struct xe_device *xe,
>  			 * Advance rules until we find XE_RTP_MATCH_OR to check
>  			 * if there's another set of conditions to check
>  			 */
> -			while (i < n_rules && rules[++i].match_type != XE_RTP_MATCH_OR)
> +			while (++i < n_rules && rules[i].match_type != XE_RTP_MATCH_OR)
>  				;
>  
>  			if (i >= n_rules)
> -- 
> 2.43.0
>