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

commit daac07156b330b18eb5071aec4b3ddca1c377f2c upstream.

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.

Change-Id: Ifa5b3c5177dd5a3c93e4523516014664313e7523
Reported-by: Hui Peng <benquike@gmail.com>
Reported-by: Mathias Payer <mathias.payer@nebelwelt.net>
Signed-off-by: Hui Peng <benquike@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
This commit is contained in:
Hui Peng 2019-08-13 22:34:04 -04:00 committed by syphyr
parent 3af93eb827
commit 70350d071d
1 changed files with 3 additions and 1 deletions
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4
sound/usb/mixer.c
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@ -1528,7 +1528,9 @@ static int parse_audio_mixer_unit(struct mixer_build *state, int unitid, void *r
int input_pins, num_ins, num_outs;
int pin, ich, err;
if (desc->bLength < 11 || ! (input_pins = desc->bNrInPins) || ! (num_outs = uac_mixer_unit_bNrChannels(desc))) {
if (desc->bLength < 11 || !(input_pins = desc->bNrInPins) ||
desc->bLength < sizeof(*desc) + desc->bNrInPins ||
!(num_outs = uac_mixer_unit_bNrChannels(desc))) {
snd_printk(KERN_ERR "invalid MIXER UNIT descriptor %d\n", unitid);
return -EINVAL;
}