ALSA: usb-audio: Fix an OOB bug in parse_audio_mixer_unit

The `uac_mixer_unit_descriptor` shown as below is read from the
device side. In `parse_audio_mixer_unit`, `baSourceID` field is
accessed from index 0 to `bNrInPins` - 1, the current implementation
assumes that descriptor is always valid (the length  of descriptor
is no shorter than 5 + `bNrInPins`). If a descriptor read from
the device side is invalid, it may trigger out-of-bound memory

struct uac_mixer_unit_descriptor {
	__u8 bLength;
	__u8 bDescriptorType;
	__u8 bDescriptorSubtype;
	__u8 bUnitID;
	__u8 bNrInPins;
	__u8 baSourceID[];

This patch fixes the bug by add a sanity check on the length of
the descriptor.

Reported-by: Hui Peng <>
Reported-by: Mathias Payer <>
Cc: <>
Signed-off-by: Hui Peng <>
Signed-off-by: Takashi Iwai <>
1 file changed