ALSA: usb-audio: Add input value sanity checks for standard types

For an invalid input value that is out of the given range, currently
USB-audio driver corrects the value silently and accepts without
errors. This is no wrong behavior, per se, but the recent kselftest
rather wants to have an error in such a case, hence a different
behavior is expected now.

This patch adds a sanity check at each control put for the standard
mixer types and returns an error if an invalid value is given.

Note that this covers only the standard mixer types. The mixer quirks
that have own control callbacks would need different coverage.

Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Takashi Iwai <[e-mail]>

sound/usb/mixer.c

···
 
 #define get_min_max(cval, def)	get_min_max_with_quirks(cval, def, NULL)
 
+/* get the max value advertised via control API */
+static int get_max_exposed(struct usb_mixer_elem_info *cval)
+{
+	if (!cval->max_exposed) {
+		if (cval->res)
+			cval->max_exposed =
+				DIV_ROUND_UP(cval->max - cval->min, cval->res);
+		else
+			cval->max_exposed = cval->max - cval->min;
+	}
+	return cval->max_exposed;
+}
+
 /* get a feature/mixer unit info */
 static int mixer_ctl_feature_info(struct snd_kcontrol *kcontrol,
 				  struct snd_ctl_elem_info *uinfo)
···
 	else
 		uinfo->type = SNDRV_CTL_ELEM_TYPE_INTEGER;
 	uinfo->count = cval->channels;
-	if (cval->val_type == USB_MIXER_BOOLEAN ||
-	    cval->val_type == USB_MIXER_INV_BOOLEAN) {
-		uinfo->value.integer.min = 0;
-		uinfo->value.integer.max = 1;
-	} else {
+	if (cval->val_type != USB_MIXER_BOOLEAN &&
+	    cval->val_type != USB_MIXER_INV_BOOLEAN) {
 		if (!cval->initialized) {
 			get_min_max_with_quirks(cval, 0, kcontrol);
 			if (cval->initialized && cval->dBmin >= cval->dBmax) {
···
 					       &kcontrol->id);
 			}
 		}
-		uinfo->value.integer.min = 0;
-		uinfo->value.integer.max =
-			DIV_ROUND_UP(cval->max - cval->min, cval->res);
 	}
+
+	uinfo->value.integer.min = 0;
+	uinfo->value.integer.max = get_max_exposed(cval);
 	return 0;
 }
 
···
 				 struct snd_ctl_elem_value *ucontrol)
 {
 	struct usb_mixer_elem_info *cval = kcontrol->private_data;
+	int max_val = get_max_exposed(cval);
 	int c, cnt, val, oval, err;
 	int changed = 0;
 
···
 			if (err < 0)
 				return filter_error(cval, err);
 			val = ucontrol->value.integer.value[cnt];
+			if (val < 0 || val > max_val)
+				return -EINVAL;
 			val = get_abs_value(cval, val);
 			if (oval != val) {
 				snd_usb_set_cur_mix_value(cval, c + 1, cnt, val);
···
 		if (err < 0)
 			return filter_error(cval, err);
 		val = ucontrol->value.integer.value[0];
+		if (val < 0 || val > max_val)
+			return -EINVAL;
 		val = get_abs_value(cval, val);
 		if (val != oval) {
 			snd_usb_set_cur_mix_value(cval, 0, 0, val);
···
 	if (err < 0)
 		return filter_error(cval, err);
 	val = ucontrol->value.integer.value[0];
+	if (val < 0 || val > get_max_exposed(cval))
+		return -EINVAL;
 	val = get_abs_value(cval, val);
 	if (val != oval) {
 		set_cur_ctl_value(cval, cval->control << 8, val);
···
 	if (err < 0)
 		return filter_error(cval, err);
 	val = ucontrol->value.enumerated.item[0];
+	if (val < 0 || val >= cval->max) /* here cval->max = # elements */
+		return -EINVAL;
 	val = get_abs_value(cval, val);
 	if (val != oval) {
 		set_cur_ctl_value(cval, cval->control << 8, val);

sound/usb/mixer.h

···
 	int channels;
 	int val_type;
 	int min, max, res;
+	int max_exposed; /* control API exposes the value in 0..max_exposed */
 	int dBmin, dBmax;
 	int cached;
 	int cache_val[MAX_CHANNELS];