ALSA: usb-audio: Fix memory leak and corruption in mixer_us16x08.c

There are a few places leaking memory and doing double-free in
mixer_us16x08.c.

The driver allocates a usb_mixer_elem_info object at each
add_new_ctl() call.  This has to be freed via kctl->private_free, but
currently this is done properly only for some controls.

Also, the driver allocates three external objects (comp_store,
eq_store, meter_store), and these are referred in elem->private_data
(it's not kctl->private_data).  And these have to be released, but
there are none doing it.  Moreover, these extra objects have to be
released only once.  Thus the release should be done only by the first
kctl element that refers to it.

For fixing these, we call either snd_usb_mixer_elem_free() (only for
kctl->private_data) or elem_private_free() (for both
kctl->private_data and elem->private_data) via kctl->private_free
appropriately.

Last but not least, snd_us16x08_controls_create() may return in the
middle without releasing the allocated *_store objects due to an
error.  For fixing this, we shuffle the allocation code so that it's
called just before its reference.

Fixes: d2bb390a2081 ("ALSA: usb-audio: Tascam US-16x08 DSP mixer quirk")
Reported-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Reviewed-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/usb/mixer_us16x08.c b/sound/usb/mixer_us16x08.c
index 73a0b9a..f728954 100644
--- a/sound/usb/mixer_us16x08.c
+++ b/sound/usb/mixer_us16x08.c
@@ -1053,11 +1053,22 @@
 
 }
 
+/* release elem->private_free as well; called only once for each *_store */
+static void elem_private_free(struct snd_kcontrol *kctl)
+{
+	struct usb_mixer_elem_info *elem = kctl->private_data;
+
+	if (elem)
+		kfree(elem->private_data);
+	kfree(elem);
+	kctl->private_data = NULL;
+}
+
 static int add_new_ctl(struct usb_mixer_interface *mixer,
 	const struct snd_kcontrol_new *ncontrol,
 	int index, int val_type, int channels,
 	const char *name, const void *opt,
-	void (*freeer)(struct snd_kcontrol *kctl),
+	bool do_private_free,
 	struct usb_mixer_elem_info **elem_ret)
 {
 	struct snd_kcontrol *kctl;
@@ -1085,7 +1096,10 @@
 		return -ENOMEM;
 	}
 
-	kctl->private_free = freeer;
+	if (do_private_free)
+		kctl->private_free = elem_private_free;
+	else
+		kctl->private_free = snd_usb_mixer_elem_free;
 
 	strlcpy(kctl->id.name, name, sizeof(kctl->id.name));
 
@@ -1109,7 +1123,6 @@
 		.type = USB_MIXER_BOOLEAN,
 		.num_channels = 16,
 		.name = "EQ Switch",
-		.freeer = snd_usb_mixer_elem_free
 	},
 	{ /* EQ low gain */
 		.kcontrol_new = &snd_us16x08_eq_gain_ctl,
@@ -1117,7 +1130,6 @@
 		.type = USB_MIXER_U8,
 		.num_channels = 16,
 		.name = "EQ Low Volume",
-		.freeer = snd_usb_mixer_elem_free
 	},
 	{ /* EQ low freq */
 		.kcontrol_new = &snd_us16x08_eq_low_freq_ctl,
@@ -1125,7 +1137,6 @@
 		.type = USB_MIXER_U8,
 		.num_channels = 16,
 		.name = "EQ Low Frequence",
-		.freeer = NULL
 	},
 	{ /* EQ mid low gain */
 		.kcontrol_new = &snd_us16x08_eq_gain_ctl,
@@ -1133,7 +1144,6 @@
 		.type = USB_MIXER_U8,
 		.num_channels = 16,
 		.name = "EQ MidLow Volume",
-		.freeer = snd_usb_mixer_elem_free
 	},
 	{ /* EQ mid low freq */
 		.kcontrol_new = &snd_us16x08_eq_mid_freq_ctl,
@@ -1141,7 +1151,6 @@
 		.type = USB_MIXER_U8,
 		.num_channels = 16,
 		.name = "EQ MidLow Frequence",
-		.freeer = NULL
 	},
 	{ /* EQ mid low Q */
 		.kcontrol_new = &snd_us16x08_eq_mid_width_ctl,
@@ -1149,7 +1158,6 @@
 		.type = USB_MIXER_U8,
 		.num_channels = 16,
 		.name = "EQ MidQLow Q",
-		.freeer = NULL
 	},
 	{ /* EQ mid high gain */
 		.kcontrol_new = &snd_us16x08_eq_gain_ctl,
@@ -1157,7 +1165,6 @@
 		.type = USB_MIXER_U8,
 		.num_channels = 16,
 		.name = "EQ MidHigh Volume",
-		.freeer = snd_usb_mixer_elem_free
 	},
 	{ /* EQ mid high freq */
 		.kcontrol_new = &snd_us16x08_eq_mid_freq_ctl,
@@ -1165,7 +1172,6 @@
 		.type = USB_MIXER_U8,
 		.num_channels = 16,
 		.name = "EQ MidHigh Frequence",
-		.freeer = NULL
 	},
 	{ /* EQ mid high Q */
 		.kcontrol_new = &snd_us16x08_eq_mid_width_ctl,
@@ -1173,7 +1179,6 @@
 		.type = USB_MIXER_U8,
 		.num_channels = 16,
 		.name = "EQ MidHigh Q",
-		.freeer = NULL
 	},
 	{ /* EQ high gain */
 		.kcontrol_new = &snd_us16x08_eq_gain_ctl,
@@ -1181,7 +1186,6 @@
 		.type = USB_MIXER_U8,
 		.num_channels = 16,
 		.name = "EQ High Volume",
-		.freeer = snd_usb_mixer_elem_free
 	},
 	{ /* EQ low freq */
 		.kcontrol_new = &snd_us16x08_eq_high_freq_ctl,
@@ -1189,7 +1193,6 @@
 		.type = USB_MIXER_U8,
 		.num_channels = 16,
 		.name = "EQ High Frequence",
-		.freeer = NULL
 	},
 };
 
@@ -1201,7 +1204,6 @@
 		.type = USB_MIXER_BOOLEAN,
 		.num_channels = 16,
 		.name = "Compressor Switch",
-		.freeer = snd_usb_mixer_elem_free
 	},
 	{ /* Comp threshold */
 		.kcontrol_new = &snd_us16x08_comp_threshold_ctl,
@@ -1209,7 +1211,6 @@
 		.type = USB_MIXER_U8,
 		.num_channels = 16,
 		.name = "Compressor Threshold Volume",
-		.freeer = NULL
 	},
 	{ /* Comp ratio */
 		.kcontrol_new = &snd_us16x08_comp_ratio_ctl,
@@ -1217,7 +1218,6 @@
 		.type = USB_MIXER_U8,
 		.num_channels = 16,
 		.name = "Compressor Ratio",
-		.freeer = NULL
 	},
 	{ /* Comp attack */
 		.kcontrol_new = &snd_us16x08_comp_attack_ctl,
@@ -1225,7 +1225,6 @@
 		.type = USB_MIXER_U8,
 		.num_channels = 16,
 		.name = "Compressor Attack",
-		.freeer = NULL
 	},
 	{ /* Comp release */
 		.kcontrol_new = &snd_us16x08_comp_release_ctl,
@@ -1233,7 +1232,6 @@
 		.type = USB_MIXER_U8,
 		.num_channels = 16,
 		.name = "Compressor Release",
-		.freeer = NULL
 	},
 	{ /* Comp gain */
 		.kcontrol_new = &snd_us16x08_comp_gain_ctl,
@@ -1241,7 +1239,6 @@
 		.type = USB_MIXER_U8,
 		.num_channels = 16,
 		.name = "Compressor Volume",
-		.freeer = NULL
 	},
 };
 
@@ -1253,7 +1250,6 @@
 		.type = USB_MIXER_BOOLEAN,
 		.num_channels = 16,
 		.name = "Phase Switch",
-		.freeer = snd_usb_mixer_elem_free,
 		.default_val = 0
 	},
 	{ /* Fader */
@@ -1262,7 +1258,6 @@
 		.type = USB_MIXER_U8,
 		.num_channels = 16,
 		.name = "Line Volume",
-		.freeer = NULL,
 		.default_val = 127
 	},
 	{ /* Mute */
@@ -1271,7 +1266,6 @@
 		.type = USB_MIXER_BOOLEAN,
 		.num_channels = 16,
 		.name = "Mute Switch",
-		.freeer = NULL,
 		.default_val = 0
 	},
 	{ /* Pan */
@@ -1280,7 +1274,6 @@
 		.type = USB_MIXER_U16,
 		.num_channels = 16,
 		.name = "Pan Left-Right Volume",
-		.freeer = NULL,
 		.default_val = 127
 	},
 };
@@ -1293,7 +1286,6 @@
 		.type = USB_MIXER_U8,
 		.num_channels = 16,
 		.name = "Master Volume",
-		.freeer = NULL,
 		.default_val = 127
 	},
 	{ /* Bypass */
@@ -1302,7 +1294,6 @@
 		.type = USB_MIXER_BOOLEAN,
 		.num_channels = 16,
 		.name = "DSP Bypass Switch",
-		.freeer = NULL,
 		.default_val = 0
 	},
 	{ /* Buss out */
@@ -1311,7 +1302,6 @@
 		.type = USB_MIXER_BOOLEAN,
 		.num_channels = 16,
 		.name = "Buss Out Switch",
-		.freeer = NULL,
 		.default_val = 0
 	},
 	{ /* Master mute */
@@ -1320,7 +1310,6 @@
 		.type = USB_MIXER_BOOLEAN,
 		.num_channels = 16,
 		.name = "Master Mute Switch",
-		.freeer = NULL,
 		.default_val = 0
 	},
 
@@ -1338,30 +1327,10 @@
 	/* just check for non-MIDI interface */
 	if (mixer->hostif->desc.bInterfaceNumber == 3) {
 
-		/* create compressor mixer elements */
-		comp_store = snd_us16x08_create_comp_store();
-		if (comp_store == NULL)
-			return -ENOMEM;
-
-		/* create eq store */
-		eq_store = snd_us16x08_create_eq_store();
-		if (eq_store == NULL) {
-			kfree(comp_store);
-			return -ENOMEM;
-		}
-
-		/* create meters store */
-		meter_store = snd_us16x08_create_meter_store();
-		if (meter_store == NULL) {
-			kfree(comp_store);
-			kfree(eq_store);
-			return -ENOMEM;
-		}
-
 		/* add routing control */
 		err = add_new_ctl(mixer, &snd_us16x08_route_ctl,
 			SND_US16X08_ID_ROUTE, USB_MIXER_U8, 8, "Line Out Route",
-			NULL, NULL, &elem);
+			NULL, false, &elem);
 		if (err < 0) {
 			usb_audio_dbg(mixer->chip,
 				"Failed to create route control, err:%d\n",
@@ -1372,6 +1341,11 @@
 			elem->cache_val[i] = i < 2 ? i : i + 2;
 		elem->cached = 0xff;
 
+		/* create compressor mixer elements */
+		comp_store = snd_us16x08_create_comp_store();
+		if (!comp_store)
+			return -ENOMEM;
+
 		/* add master controls */
 		for (i = 0;
 			i < sizeof(master_controls)
@@ -1385,7 +1359,8 @@
 				master_controls[i].num_channels,
 				master_controls[i].name,
 				comp_store,
-				master_controls[i].freeer, &elem);
+				i == 0, /* release comp_store only once */
+				&elem);
 			if (err < 0)
 				return err;
 			elem->cache_val[0] = master_controls[i].default_val;
@@ -1405,7 +1380,7 @@
 				channel_controls[i].num_channels,
 				channel_controls[i].name,
 				comp_store,
-				channel_controls[i].freeer, &elem);
+				false, &elem);
 			if (err < 0)
 				return err;
 			for (j = 0; j < SND_US16X08_MAX_CHANNELS; j++) {
@@ -1415,6 +1390,11 @@
 			elem->cached = 0xffff;
 		}
 
+		/* create eq store */
+		eq_store = snd_us16x08_create_eq_store();
+		if (!eq_store)
+			return -ENOMEM;
+
 		/* add EQ controls */
 		for (i = 0; i < sizeof(eq_controls) /
 			sizeof(control_params); i++) {
@@ -1426,7 +1406,8 @@
 				eq_controls[i].num_channels,
 				eq_controls[i].name,
 				eq_store,
-				eq_controls[i].freeer, NULL);
+				i == 0, /* release eq_store only once */
+				NULL);
 			if (err < 0)
 				return err;
 		}
@@ -1444,18 +1425,23 @@
 				comp_controls[i].num_channels,
 				comp_controls[i].name,
 				comp_store,
-				comp_controls[i].freeer, NULL);
+				false, NULL);
 			if (err < 0)
 				return err;
 		}
 
+		/* create meters store */
+		meter_store = snd_us16x08_create_meter_store();
+		if (!meter_store)
+			return -ENOMEM;
+
 		/* meter function 'get' must access to compressor store
 		 * so place a reference here
 		 */
 		meter_store->comp_store = comp_store;
 		err = add_new_ctl(mixer, &snd_us16x08_meter_ctl,
 			SND_US16X08_ID_METER, USB_MIXER_U16, 0, "Level Meter",
-			(void *) meter_store, snd_usb_mixer_elem_free, NULL);
+			meter_store, true, NULL);
 		if (err < 0)
 			return err;
 	}