The entry of the validators table for UAC3 AC header descriptor is
defined with the wrong protocol version UAC_VERSION_2, while it should
have been UAC_VERSION_3.  This results in the validator never matching
for actual UAC3 devices (protocol == UAC_VERSION_3), causing their
header descriptors to bypass validation entirely.  A malicious USB
device presenting a truncated UAC3 header could exploit this to cause
out-of-bounds reads when the driver later accesses unvalidated
descriptor fields.

The bug was introduced in the same commit as the recently fixed UAC3
feature unit sub-type typo, and appears to be from the same copy-paste
error when the UAC3 section was created from the UAC2 section.

Fixes: 57f8770620e9 ("ALSA: usb-audio: More validations of descriptor units")
Cc: <stable@vger.kernel.org>
Signed-off-by: Jun Seo <jun.seo.93@proton.me>
---
 sound/usb/validate.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sound/usb/validate.c b/sound/usb/validate.c
index 4bb4893f6e74..f62b7cc041dc 100644
--- a/sound/usb/validate.c
+++ b/sound/usb/validate.c
@@ -281,7 +281,7 @@ static const struct usb_desc_validator audio_validators[] = {
 	/* UAC_VERSION_2, UAC2_SAMPLE_RATE_CONVERTER: not implemented yet */
 
 	/* UAC3 */
-	FIXED(UAC_VERSION_2, UAC_HEADER, struct uac3_ac_header_descriptor),
+	FIXED(UAC_VERSION_3, UAC_HEADER, struct uac3_ac_header_descriptor),
 	FIXED(UAC_VERSION_3, UAC_INPUT_TERMINAL,
 	      struct uac3_input_terminal_descriptor),
 	FIXED(UAC_VERSION_3, UAC_OUTPUT_TERMINAL,
-- 
2.53.0

On Thu, 26 Feb 2026 02:08:20 +0100,
Jun Seo wrote:
> 
> The entry of the validators table for UAC3 AC header descriptor is
> defined with the wrong protocol version UAC_VERSION_2, while it should
> have been UAC_VERSION_3.  This results in the validator never matching
> for actual UAC3 devices (protocol == UAC_VERSION_3), causing their
> header descriptors to bypass validation entirely.  A malicious USB
> device presenting a truncated UAC3 header could exploit this to cause
> out-of-bounds reads when the driver later accesses unvalidated
> descriptor fields.
> 
> The bug was introduced in the same commit as the recently fixed UAC3
> feature unit sub-type typo, and appears to be from the same copy-paste
> error when the UAC3 section was created from the UAC2 section.
> 
> Fixes: 57f8770620e9 ("ALSA: usb-audio: More validations of descriptor units")
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Jun Seo <jun.seo.93@proton.me>

Thanks, applied now.


Takashi