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Date:   Fri, 22 Sep 2023 20:16:16 -0600
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Subject: Re: [PATCH 6/9] drm/vc4: Annotate struct vc4_perfmon with
 __counted_by
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To:     Kees Cook <keescook@chromium.org>, David Airlie <airlied@gmail.com>
Cc:     Emma Anholt <emma@anholt.net>, Maxime Ripard <mripard@kernel.org>,
        Daniel Vetter <daniel@ffwll.ch>,
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References: <20230922173110.work.084-kees@kernel.org>
 <20230922173216.3823169-6-keescook@chromium.org>
From:   "Gustavo A. R. Silva" <gustavo@embeddedor.com>
In-Reply-To: <20230922173216.3823169-6-keescook@chromium.org>
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On 9/22/23 11:32, Kees Cook wrote:
> Prepare for the coming implementation by GCC and Clang of the __counted_by
> attribute. Flexible array members annotated with __counted_by can have
> their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS
> (for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
> functions).
> 
> As found with Coccinelle[1], add __counted_by for struct vc4_perfmon.
> 
> [1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci
> 
> Cc: Emma Anholt <emma@anholt.net>
> Cc: Maxime Ripard <mripard@kernel.org>
> Cc: David Airlie <airlied@gmail.com>
> Cc: Daniel Vetter <daniel@ffwll.ch>
> Cc: dri-devel@lists.freedesktop.org
> Signed-off-by: Kees Cook <keescook@chromium.org>

Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>

Thanks
-- 
Gustavo

> ---
>   drivers/gpu/drm/vc4/vc4_drv.h | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/vc4/vc4_drv.h b/drivers/gpu/drm/vc4/vc4_drv.h
> index bf66499765fb..ab61e96e7e14 100644
> --- a/drivers/gpu/drm/vc4/vc4_drv.h
> +++ b/drivers/gpu/drm/vc4/vc4_drv.h
> @@ -76,7 +76,7 @@ struct vc4_perfmon {
>   	 * Note that counter values can't be reset, but you can fake a reset by
>   	 * destroying the perfmon and creating a new one.
>   	 */
> -	u64 counters[];
> +	u64 counters[] __counted_by(ncounters);
>   };
>   
>   struct vc4_dev {