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.
CVE: CVE-2018-15117
Reported-by: Hui Peng <benquike@xxxxxxxxx>
Reported-by: Mathias Payer <mathias.payer@xxxxxxxxxxxxx>
Signed-off-by: Hui Peng <benquike@xxxxxxxxx>
---
sound/usb/mixer.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c
index 1f7eb3816cd7..10ddec76f906 100644
--- a/sound/usb/mixer.c
+++ b/sound/usb/mixer.c
@@ -1628,6 +1628,7 @@ static int parse_audio_mixer_unit(struct mixer_build *state, int unitid,
int pin, ich, err;
if (desc->bLength < 11 || !(input_pins = desc->bNrInPins) ||
+ desc->bLength < sizeof(*desc) + desc->bNrInPins ||
!(num_outs = uac_mixer_unit_bNrChannels(desc))) {
usb_audio_err(state->chip,
"invalid MIXER UNIT descriptor %d\n",
--
2.17.1
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