sound: ua101: fix division by zero at probe

commit d1f73f1 upstream.

Add a missing sanity check for bNrChannels in detect_usb_format()
to prevent a division by zero in playback_urb_complete() and
capture_urb_complete().

USB core does not validate class-specific descriptor fields such
as bNrChannels, so drivers must verify them before use. If a
device provides bNrChannels = 0, frame_bytes becomes zero and is
later used as a divisor in the URB completion handlers, leading
to a kernel crash.

Fixes: 63978ab ("sound: add Edirol UA-101 support")
Cc: stable@vger.kernel.org
Signed-off-by: SeungJu Cheon <suunj1331@gmail.com>
Link: https://patch.msgid.link/20260426111239.103296-1-suunj1331@gmail.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: suunj

sound/usb/misc/ua101.c

@@ -974,6 +974,13 @@ static int detect_usb_format(struct ua101 *ua)
 
 	ua->capture.channels = fmt_capture->bNrChannels;
 	ua->playback.channels = fmt_playback->bNrChannels;
+	if (!ua->capture.channels || !ua->playback.channels) {
+		dev_err(&ua->dev->dev,
+			"invalid channel count: capture %u, playback %u\n",
+			ua->capture.channels, ua->playback.channels);
+		return -EINVAL;
+	}
+
 	ua->capture.frame_bytes =
 		fmt_capture->bSubframeSize * ua->capture.channels;
 	ua->playback.frame_bytes =