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

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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>
This commit is contained in:
Hui Peng 2019-08-13 22:34:04 -04:00 committed by Takashi Iwai
parent 871b906602
commit daac07156b
1 changed files with 2 additions and 0 deletions
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2
sound/usb/mixer.c
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@ -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: