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 mcu_msg_push_buffers_internal.

[1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci

Cc: Michael Tretter <m.tretter@pengutronix.de>
Cc: Pengutronix Kernel Team <kernel@pengutronix.de>
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
Cc: linux-media@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 drivers/media/platform/allegro-dvt/allegro-mail.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/media/platform/allegro-dvt/allegro-mail.h b/drivers/media/platform/allegro-dvt/allegro-mail.h
index a5686058d754..c0c9013f1aab 100644
--- a/drivers/media/platform/allegro-dvt/allegro-mail.h
+++ b/drivers/media/platform/allegro-dvt/allegro-mail.h
@@ -184,7 +184,7 @@ struct mcu_msg_push_buffers_internal {
 	struct mcu_msg_header header;
 	u32 channel_id;
 	size_t num_buffers;
-	struct mcu_msg_push_buffers_internal_buffer buffer[];
+	struct mcu_msg_push_buffers_internal_buffer buffer[] __counted_by(num_buffers);
 };
 
 struct mcu_msg_put_stream_buffer {
-- 
2.34.1

On Fri, 22 Sep 2023 10:49:36 -0700, 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 mcu_msg_push_buffers_internal.
> 
> [...]

Since this is a trivial change and it's been 2 week without further
discussion, I'll snag this patch.

Applied to for-next/hardening, thanks!

[1/1] media: allegro: Annotate struct mcu_msg_push_buffers_internal with __counted_by
      https://git.kernel.org/kees/c/63eed8dcdf49

Take care,

-- 
Kees Cook

On 9/22/23 11:49, 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 mcu_msg_push_buffers_internal.
> 
> [1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci
> 
> Cc: Michael Tretter <m.tretter@pengutronix.de>
> Cc: Pengutronix Kernel Team <kernel@pengutronix.de>
> Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
> Cc: linux-media@vger.kernel.org
> Signed-off-by: Kees Cook <keescook@chromium.org>

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

Thanks
-- 
Gustavo

> ---
>   drivers/media/platform/allegro-dvt/allegro-mail.h | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/media/platform/allegro-dvt/allegro-mail.h b/drivers/media/platform/allegro-dvt/allegro-mail.h
> index a5686058d754..c0c9013f1aab 100644
> --- a/drivers/media/platform/allegro-dvt/allegro-mail.h
> +++ b/drivers/media/platform/allegro-dvt/allegro-mail.h
> @@ -184,7 +184,7 @@ struct mcu_msg_push_buffers_internal {
>   	struct mcu_msg_header header;
>   	u32 channel_id;
>   	size_t num_buffers;
> -	struct mcu_msg_push_buffers_internal_buffer buffer[];
> +	struct mcu_msg_push_buffers_internal_buffer buffer[] __counted_by(num_buffers);
>   };
>   
>   struct mcu_msg_put_stream_buffer {