linux-kernel - Re: [PATCH] ASoC: cs-amp-lib: Annotate struct cirrus_amp_efi_data with __counted

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Message-ID: <e16b42f3-cc78-49fd-9850-d59a59b5b8e8@opensource.cirrus.com>
Date: Tue, 15 Apr 2025 10:24:49 +0100
From: Richard Fitzgerald <rf@...nsource.cirrus.com>
To: Thorsten Blum <thorsten.blum@...ux.dev>,
        David Rhodes <david.rhodes@...rus.com>,
        Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.com>,
        Kees Cook <kees@...nel.org>,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc: linux-sound@...r.kernel.org, patches@...nsource.cirrus.com,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH] ASoC: cs-amp-lib: Annotate struct cirrus_amp_efi_data
 with __counted_by()

On 15/04/2025 10:03 am, Thorsten Blum wrote:
> Add the __counted_by() compiler attribute to the flexible array member
> 'data' to improve access bounds-checking via CONFIG_UBSAN_BOUNDS and
> CONFIG_FORTIFY_SOURCE.
> 
> No functional changes intended.
> 
> Signed-off-by: Thorsten Blum <thorsten.blum@...ux.dev>
> ---
>   include/sound/cs-amp-lib.h | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/sound/cs-amp-lib.h b/include/sound/cs-amp-lib.h
> index f481148735e1..5459c221badf 100644
> --- a/include/sound/cs-amp-lib.h
> +++ b/include/sound/cs-amp-lib.h
> @@ -23,7 +23,7 @@ struct cirrus_amp_cal_data {
>   struct cirrus_amp_efi_data {
>   	u32 size;
>   	u32 count;
> -	struct cirrus_amp_cal_data data[];
> +	struct cirrus_amp_cal_data data[] __counted_by(count);
>   } __packed;
>   
>   /**

I wrote a patch to do exactly the same, but you got your patch out
first! It is identical to my patch so:

Reviewed-by: Richard Fitzgerald <rf@...nsource.cirrus.com>

(Note that I did some testing with Clang-19 and the __counted_by() seems
to only be checked in certain functions, like memcpy() and memset(). The
get_random_bytes() used in the KUnit test can overrun the array without
triggering any warning.)