staging: line6: add bounds check in snd_toneport_source_put()

"source" comes from the user in snd_ctl_elem_write() so it needs to be
checked.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Stefan Hajnoczi <stefanha@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/line6/toneport.c

@@ -244,13 +244,17 @@ static int snd_toneport_source_put(struct snd_kcontrol *kcontrol,
 	struct snd_line6_pcm *line6pcm = snd_kcontrol_chip(kcontrol);
 	struct usb_line6_toneport *toneport =
 	    (struct usb_line6_toneport *)line6pcm->line6;
+	unsigned int source;
 
-	if (ucontrol->value.enumerated.item[0] == toneport->source)
+	source = ucontrol->value.enumerated.item[0];
+	if (source >= ARRAY_SIZE(toneport_source_info))
+		return -EINVAL;
+	if (source == toneport->source)
 		return 0;
 
-	toneport->source = ucontrol->value.enumerated.item[0];
+	toneport->source = source;
 	toneport_send_cmd(toneport->line6.usbdev,
-			  toneport_source_info[toneport->source].code, 0x0000);
+			  toneport_source_info[source].code, 0x0000);
 	return 1;
 }