static int snd_usb_create_streams(struct snd_usb_audio *chip, int ctrlif)
{
	struct usb_device *dev = chip->dev;
	struct usb_host_interface *host_iface;
 	struct usb_interface_descriptor *altsd;
 	void *control_header;
 	int i, protocol;
 
 	/* find audiocontrol interface */
 	host_iface = &usb_ifnum_to_if(dev, ctrlif)->altsetting[0];
	control_header = snd_usb_find_csint_desc(host_iface->extra,
						 host_iface->extralen,
						 NULL, UAC_HEADER);
	altsd = get_iface_desc(host_iface);
	protocol = altsd->bInterfaceProtocol;

	if (!control_header) {
		dev_err(&dev->dev, "cannot find UAC_HEADER\n");
 		return -EINVAL;
 	}
 
 	switch (protocol) {
 	default:
 		dev_warn(&dev->dev,
			 "unknown interface protocol %#02x, assuming v1\n",
			 protocol);
		/* fall through */

 	case UAC_VERSION_1: {
 		struct uac1_ac_header_descriptor *h1 = control_header;
 
 		if (!h1->bInCollection) {
 			dev_info(&dev->dev, "skipping empty audio interface (v1)\n");
 			return -EINVAL;
 		}
 
 		if (h1->bLength < sizeof(*h1) + h1->bInCollection) {
 			dev_err(&dev->dev, "invalid UAC_HEADER (v1)\n");
 			return -EINVAL;
		}

		for (i = 0; i < h1->bInCollection; i++)
			snd_usb_create_stream(chip, ctrlif, h1->baInterfaceNr[i]);

		break;
	}

	case UAC_VERSION_2: {
		struct usb_interface_assoc_descriptor *assoc =
			usb_ifnum_to_if(dev, ctrlif)->intf_assoc;

		if (!assoc) {
			/*
			 * Firmware writers cannot count to three.  So to find
			 * the IAD on the NuForce UDH-100, also check the next
			 * interface.
			 */
			struct usb_interface *iface =
				usb_ifnum_to_if(dev, ctrlif + 1);
			if (iface &&
			    iface->intf_assoc &&
			    iface->intf_assoc->bFunctionClass == USB_CLASS_AUDIO &&
			    iface->intf_assoc->bFunctionProtocol == UAC_VERSION_2)
				assoc = iface->intf_assoc;
		}

		if (!assoc) {
			dev_err(&dev->dev, "Audio class v2 interfaces need an interface association\n");
			return -EINVAL;
		}

		for (i = 0; i < assoc->bInterfaceCount; i++) {
			int intf = assoc->bFirstInterface + i;

			if (intf != ctrlif)
				snd_usb_create_stream(chip, ctrlif, intf);
		}

		break;
	}
	}

	return 0;
}

The product reads data past the end, or before the beginning, of the intended buffer.