ALSA: usb-audio: Fix UAC3 cluster descriptor size check

commit 26265dd upstream.

The UAC3 cluster descriptor length check in
snd_usb_get_audioformat_uac3()was added to
make sure that the buffer is large enough for
a struct uac3_cluster_header_descriptor before the
returned data is cast and used.

However, the check uses sizeof(cluster), where cluster
is a pointer, not the size of the descriptor header.
This makes the validation depend on the architecture
pointer size and does not match the intended object size.

Check against sizeof(*cluster) instead.

Fixes: fb4e2a6 ("ALSA: usb-audio: Fix out-of-bounds read in snd_usb_get_audioformat_uac3()")
Cc: stable@vger.kernel.org
Signed-off-by: Cássio Gabriel <cassiogabrielcontato@gmail.com>
Link: https://patch.msgid.link/20260424-alsa-usb-uac3-cluster-size-v1-1-99a5808898a3@gmail.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: CassivsGabriellis

sound/usb/stream.c

@@ -998,7 +998,7 @@ snd_usb_get_audioformat_uac3(struct snd_usb_audio *chip,
 	 * and request Cluster Descriptor
 	 */
 	wLength = le16_to_cpu(hc_header.wLength);
-	if (wLength < sizeof(cluster))
+	if (wLength < sizeof(*cluster))
 		return NULL;
 	cluster = kzalloc(wLength, GFP_KERNEL);
 	if (!cluster)