On Tue, 16 Dec 2025 07:01:56 +0100, Shipei Qu wrote:

Hi,

resending with a properly formatted diff (the previous email had a malformed patch header). The change itself is the same: while fuzzing a USB gadget that emulates a Tascam US-16x08 we found that get_meter_levels_from_urb() in mixer_us16x08.c uses a channel index taken directly from the 64-byte meter packet to index meter_level[], comp_level[] and master_level[] without any bounds checking. A malformed packet can therefore cause out-of-bounds writes in the snd_us16x08_meter_store.

A malicious USB audio device (or USB gadget implementation) that pretends to be a US-16x08-compatible interface can trigger this by sending crafted meter packets. We have a small USB gadget-based PoC for this behaviour and can share it if that would be helpful.

This driver is used by common distributions (e.g. Ubuntu) when a US-16x08 or compatible USB audio device is present. The same pattern is present in current mainline kernels.

This issue was first reported via security@kernel.org. The kernel security team explained that, in the upstream threat model, USB endpoints are expected to be trusted (i.e. only trusted devices should be bound to drivers), so they consider this a normal bug rather than a security vulnerability, and asked us to send a fix to the development lists. The patch below adds simple range checks before updating these arrays.

Reported-by: DARKNAVY (@DarkNavyOrg) vr@darknavy.com Signed-off-by: Shipei Qu qu@darknavy.com

Thanks, now it looks applicable, and the code change itself looks good.

But, could you try to rephrase the patch description above? It'll be used directly as the commit message. So it should be well descriptive about the bug and the fix, while it should concentrate on the technical issues.

You can check other commits how they look like, and also see Documentation/process/submitting-patches.rst.

thanks,

Takashi

---

sound/usb/mixer_us16x08.c | 20 ++++++++++++++------ 1 file changed, 14 insertions(+), 6 deletions(-)

diff --git a/sound/usb/mixer_us16x08.c b/sound/usb/mixer_us16x08.c index 1c5712c31..f9df40730 100644 --- a/sound/usb/mixer_us16x08.c +++ b/sound/usb/mixer_us16x08.c @@ -655,17 +655,25 @@ static void get_meter_levels_from_urb(int s, u8 *meter_urb) { int val = MUC2(meter_urb, s) + (MUC3(meter_urb, s) << 8);

• int ch = MUB2(meter_urb, s) - 1;

• if (ch < 0)

• return;
  
  

  if (MUA0(meter_urb, s) == 0x61 && MUA1(meter_urb, s) == 0x02 && MUA2(meter_urb, s) == 0x04 && MUB0(meter_urb, s) == 0x62) {

• if (MUC0(meter_urb, s) == 0x72)
  

• 	store->meter_level[MUB2(meter_urb, s) - 1] = val;
  

• if (MUC0(meter_urb, s) == 0xb2)
  

• 	store->comp_level[MUB2(meter_urb, s) - 1] = val;
  

• if (ch < SND_US16X08_MAX_CHANNELS) {
  

• 	if (MUC0(meter_urb, s) == 0x72)
  

• 		store->meter_level[ch] = val;
  

• 	if (MUC0(meter_urb, s) == 0xb2)
  

• 		store->comp_level[ch] = val;
  

• }
  

  } if (MUA0(meter_urb, s) == 0x61 && MUA1(meter_urb, s) == 0x02 &&

• MUA2(meter_urb, s) == 0x02 && MUB0(meter_urb, s) == 0x62)
  

• store->master_level[MUB2(meter_urb, s) - 1] = val;
  

• MUA2(meter_urb, s) == 0x02 && MUB0(meter_urb, s) == 0x62) {
  

• if (ch < ARRAY_SIZE(store->master_level))
  

• 	store->master_level[ch] = val;
  

• }

}

/* Function to retrieve current meter values from the device.

2.45.1