Re: [PATCH] sound: ua101: fix division by zero at probe

[M.samet Duman]

This looks reasonable to me.

Samet
> 2026. 4. 26. 오후 2:13, SeungJu Cheon <suunj1331@xxxxxxxxx> 작성:
> 
> 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: 63978ab3e3e9 ("sound: add Edirol UA-101 support")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: SeungJu Cheon <suunj1331@xxxxxxxxx>
> ---
> Testing:
> - dummy_hcd + raw_gadget emulating a UA-101 with bNrChannels=0.
> 
> sound/usb/misc/ua101.c | 7 +++++++
> 1 file changed, 7 insertions(+)
> 
> diff --git a/sound/usb/misc/ua101.c b/sound/usb/misc/ua101.c
> index 49b3dd8d827d..d129b42eb979 100644
> --- a/sound/usb/misc/ua101.c
> +++ b/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 =
> --
> 2.52.0
> 
>