ALSA: ak4xx-adda: info leak in ak4xxx_capture_source_info()

commit bd5fe738 upstream.

"idx" is controled by the user and can be a negative offset into the
input_names[] array.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Cc: Weng Meiling <wengmeiling.weng@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

sound/i2c/other/ak4xxx-adda.c

@@ -571,7 +571,7 @@ static int ak4xxx_capture_source_info(struct snd_kcontrol *kcontrol,
 	struct snd_akm4xxx *ak = snd_kcontrol_chip(kcontrol);
 	int mixer_ch = AK_GET_SHIFT(kcontrol->private_value);
 	const char **input_names;
-	int  num_names, idx;
+	unsigned int num_names, idx;
 
 	num_names = ak4xxx_capture_num_inputs(ak, mixer_ch);
 	if (!num_names)