Re: [PATCH 3/5] ALSA: control: Apply sanity check of input values for user elements

[Jaroslav Kysela <perex@perex.cz>]

On 14. 06. 24 14:47, Takashi Iwai wrote:
> Although we have already a mechanism for sanity checks of input values
> for control writes, it's not applied unless the kconfig
> CONFIG_SND_CTL_INPUT_VALIDATION is set due to the performance reason.
> Nevertheless, it still makes sense to apply the check for user
> elements despite of its cost, as that's the only way to filter out the
> invalid values; the user controls are handled solely in ALSA core
> code, and there is no corresponding driver, after all.
> 
> This patch enables the input value validation for user control
> elements no matter whether CONFIG_SND_CTL_INPUT_VALIDATION is set or
> not.  The kselftest will be happier with this change, as the incorrect
> values will be bailed out now with errors.
> 
> For other normal controls, the check is applied still only when
> CONFIG_SND_CTL_INPUT_VALIDATION is set.
> 
> Reported-by: Paul Menzel <pmenzel@molgen.mpg.de>
> Closes: https://lore.kernel.org/r/1d44be36-9bb9-4d82-8953-5ae2a4f09405@molgen.mpg.de
> Signed-off-by: Takashi Iwai <tiwai@suse.de>
> ---
>   sound/core/control.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/sound/core/control.c b/sound/core/control.c
> index fb0c60044f7b..50890983d7e2 100644
> --- a/sound/core/control.c
> +++ b/sound/core/control.c
> @@ -1317,7 +1317,8 @@ static int snd_ctl_elem_write(struct snd_card *card, struct snd_ctl_file *file,
>   	snd_ctl_build_ioff(&control->id, kctl, index_offset);
>   	result = snd_power_ref_and_wait(card);
>   	/* validate input values */
> -	if (IS_ENABLED(CONFIG_SND_CTL_INPUT_VALIDATION) && !result) {
> +	if ((IS_ENABLED(CONFIG_SND_CTL_INPUT_VALIDATION) ||
> +	     (vd->access & SNDRV_CTL_ELEM_ACCESS_USER)) && !result) {
>   		struct snd_ctl_elem_info info;

The info structure for user elements may be used directly without this 
intermediate variable for the validation. But it may be a possible future 
improvement.

					Jaroslav

-- 
Jaroslav Kysela <perex@perex.cz>
Linux Sound Maintainer; ALSA Project; Red Hat, Inc.