ALSA: usb-audio: Fix an out-of-bounds bug in __snd_usb_parse_audio_interface()

There may be a bad USB audio device with a USB ID of (0x04fa, 0x4201) and
the number of it's interfaces less than 4, an out-of-bounds read bug occurs
when parsing the interface descriptor for this device.

Fix this by checking the number of interfaces.

Signed-off-by: Dongxiang Ke <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Takashi Iwai <[email protected]>

Author: xdek42

sound/usb/stream.c

@@ -1106,7 +1106,7 @@ static int __snd_usb_parse_audio_interface(struct snd_usb_audio *chip,
 	 * Dallas DS4201 workaround: It presents 5 altsettings, but the last
 	 * one misses syncpipe, and does not produce any sound.
 	 */
-	if (chip->usb_id == USB_ID(0x04fa, 0x4201))
+	if (chip->usb_id == USB_ID(0x04fa, 0x4201) && num >= 4)
 		num = 4;
 
 	for (i = 0; i < num; i++) {