Commit daac0715 authored Aug 13, 2019 by Hui Peng Committed by Takashi Iwai Aug 14, 2019

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
access.

```
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 <benquike@gmail.com>
Reported-by: Mathias Payer <mathias.payer@nebelwelt.net>
Cc: <stable@vger.kernel.org>
Signed-off-by: Hui Peng <benquike@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

parent 871b9066

sound/usb/mixer.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -744,6 +744,8 @@ static int uac_mixer_unit_get_channels(struct mixer_build *state,
		return -EINVAL;
		if (!desc->bNrInPins)
		return -EINVAL;
		if (desc->bLength < sizeof(*desc) + desc->bNrInPins)
		return -EINVAL;

		switch (state->mixer->protocol) {
		case UAC_VERSION_1:

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