linux-kernel - Re: [PATCH] ASoC: dapm: fix bounds checker error in dapm_widget_list

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Message-ID: <987b8806-2ec7-41f7-bdeb-8f843c34a993@linux.intel.com>
Date: Tue, 29 Oct 2024 10:50:21 +0100
From: Amadeusz Sławiński
 <amadeuszx.slawinski@...ux.intel.com>
To: Aleksei Vetrov <vvvvvv@...gle.com>, Liam Girdwood <lgirdwood@...il.com>,
 Mark Brown <broonie@...nel.org>, 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, linux-kernel@...r.kernel.org,
 linux-hardening@...r.kernel.org
Subject: Re: [PATCH] ASoC: dapm: fix bounds checker error in
 dapm_widget_list_create

On 10/28/2024 11:50 PM, Aleksei Vetrov wrote:
> The widgets array in the snd_soc_dapm_widget_list has a __counted_by
> attribute attached to it, which points to the num_widgets variable. This
> attribute is used in bounds checking, and if it is not set before the
> array is filled, then the bounds sanitizer will issue a warning or a
> kernel panic if CONFIG_UBSAN_TRAP is set.
> 
> This patch sets the size of the widgets list calculated with
> list_for_each as the initial value for num_widgets as it is used for
> allocating memory for the array. It is updated with the actual number of
> added elements after the array is filled.
> 
> Signed-off-by: Aleksei Vetrov <vvvvvv@...gle.com>
> ---
>   sound/soc/soc-dapm.c | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/sound/soc/soc-dapm.c b/sound/soc/soc-dapm.c
> index c34934c31ffec3970b34b24dcaa0826dfb7d8e86..99521c784a9b16a232a558029a2f3e88bd8ebfb1 100644
> --- a/sound/soc/soc-dapm.c
> +++ b/sound/soc/soc-dapm.c
> @@ -1147,6 +1147,8 @@ static int dapm_widget_list_create(struct snd_soc_dapm_widget_list **list,
>   	if (*list == NULL)
>   		return -ENOMEM;
>   
> +	(*list)->num_widgets = size;
> +
>   	list_for_each_entry(w, widgets, work_list)
>   		(*list)->widgets[i++] = w;
>   

and after that there is (*list)->num_widgets = i;

Can this be somehow simplified to remove 'i', if it set before assignment?