Re: [PATCH] ASoC: soc-dapm: Annotate struct snd_soc_dapm_widget_list with __counted_by

["Gustavo A. R. Silva" <gustavo@embeddedor.com>]

On 10/4/23 01:28, 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 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 snd_soc_dapm_widget_list.
> Additionally, since the element count member must be set before accessing
> the annotated flexible array member, move its initialization earlier.
> 
> Cc: Liam Girdwood <lgirdwood@gmail.com>
> Cc: Mark Brown <broonie@kernel.org>
> Cc: Jaroslav Kysela <perex@perex.cz>
> Cc: Takashi Iwai <tiwai@suse.com>
> Cc: "Gustavo A. R. Silva" <gustavoars@kernel.org>
> Cc: alsa-devel@alsa-project.org
> Cc: linux-hardening@vger.kernel.org
> Link: https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci [1]
> Signed-off-by: Kees Cook <keescook@chromium.org>

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

Thanks
--
Gustavo

> ---
>   include/sound/soc-dapm.h | 2 +-
>   sound/soc/soc-dapm.c     | 2 +-
>   2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/include/sound/soc-dapm.h b/include/sound/soc-dapm.h
> index d2faec9a323e..51516c93916e 100644
> --- a/include/sound/soc-dapm.h
> +++ b/include/sound/soc-dapm.h
> @@ -717,7 +717,7 @@ struct snd_soc_dapm_context {
>   /* A list of widgets associated with an object, typically a snd_kcontrol */
>   struct snd_soc_dapm_widget_list {
>   	int num_widgets;
> -	struct snd_soc_dapm_widget *widgets[];
> +	struct snd_soc_dapm_widget *widgets[] __counted_by(num_widgets);
>   };
>   
>   #define for_each_dapm_widgets(list, i, widget)				\
> diff --git a/sound/soc/soc-dapm.c b/sound/soc/soc-dapm.c
> index 2512aadf95f7..2e3df47c9cf3 100644
> --- a/sound/soc/soc-dapm.c
> +++ b/sound/soc/soc-dapm.c
> @@ -497,8 +497,8 @@ static int dapm_kcontrol_add_widget(struct snd_kcontrol *kcontrol,
>   	if (!new_wlist)
>   		return -ENOMEM;
>   
> -	new_wlist->widgets[n - 1] = widget;
>   	new_wlist->num_widgets = n;
> +	new_wlist->widgets[n - 1] = widget;
>   
>   	data->wlist = new_wlist;
>