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

[Takashi Iwai <tiwai@xxxxxxx>]

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@xxxxxxxxxxxxx>
Closes: https://lore.kernel.org/r/1d44be36-9bb9-4d82-8953-5ae2a4f09405@xxxxxxxxxxxxx
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
---
 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;
 
 		memset(&info, 0, sizeof(info));
-- 
2.43.0