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

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

[SeungJu Cheon]

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@vger.kernel.org
Signed-off-by: SeungJu Cheon <suunj1331@gmail.com>
---
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

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

[Takashi Iwai]

On Sun, 26 Apr 2026 13:12:39 +0200,
SeungJu Cheon wrote:
> 
> 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@vger.kernel.org
> Signed-off-by: SeungJu Cheon <suunj1331@gmail.com>

Thanks, applied now.


Takashi

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@gmail.com> 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@vger.kernel.org
> Signed-off-by: SeungJu Cheon <suunj1331@gmail.com>
> ---
> 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
> 
> 

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

[Johan Hovold]

Add the missing endpoint max-packet sanity check to probe() to avoid
division by zero in alloc_stream_buffers() in case a malicious device
has broken descriptors (or when doing descriptor fuzz testing).

Note that USB core will reject URBs submitted for endpoints with zero
wMaxPacketSize but that drivers doing packet-size calculations still
need to handle this (cf. commit 2548288b4fb0 ("USB: Fix: Don't skip
endpoint descriptors with maxpacket=0")).

Fixes: 63978ab3e3e9 ("sound: add Edirol UA-101 support")
Cc: stable@vger.kernel.org      # 2.6.34
Signed-off-by: Johan Hovold <johan@kernel.org>
---
 sound/usb/misc/ua101.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/sound/usb/misc/ua101.c b/sound/usb/misc/ua101.c
index 5834d1dc317e..4f6b20ed29dd 100644
--- a/sound/usb/misc/ua101.c
+++ b/sound/usb/misc/ua101.c
@@ -1000,7 +1000,7 @@ static int detect_usb_format(struct ua101 *ua)
 		fmt_playback->bSubframeSize * ua->playback.channels;
 
 	epd = &ua->intf[INTF_CAPTURE]->altsetting[1].endpoint[0].desc;
-	if (!usb_endpoint_is_isoc_in(epd)) {
+	if (!usb_endpoint_is_isoc_in(epd) || usb_endpoint_maxp(epd) == 0) {
 		dev_err(&ua->dev->dev, "invalid capture endpoint\n");
 		return -ENXIO;
 	}
@@ -1008,7 +1008,7 @@ static int detect_usb_format(struct ua101 *ua)
 	ua->capture.max_packet_bytes = usb_endpoint_maxp(epd);
 
 	epd = &ua->intf[INTF_PLAYBACK]->altsetting[1].endpoint[0].desc;
-	if (!usb_endpoint_is_isoc_out(epd)) {
+	if (!usb_endpoint_is_isoc_out(epd) || usb_endpoint_maxp(epd) == 0) {
 		dev_err(&ua->dev->dev, "invalid playback endpoint\n");
 		return -ENXIO;
 	}
-- 
2.32.0

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

[Takashi Iwai]

On Tue, 26 Oct 2021 11:54:01 +0200,
Johan Hovold wrote:
> 
> Add the missing endpoint max-packet sanity check to probe() to avoid
> division by zero in alloc_stream_buffers() in case a malicious device
> has broken descriptors (or when doing descriptor fuzz testing).
> 
> Note that USB core will reject URBs submitted for endpoints with zero
> wMaxPacketSize but that drivers doing packet-size calculations still
> need to handle this (cf. commit 2548288b4fb0 ("USB: Fix: Don't skip
> endpoint descriptors with maxpacket=0")).
> 
> Fixes: 63978ab3e3e9 ("sound: add Edirol UA-101 support")
> Cc: stable@vger.kernel.org      # 2.6.34
> Signed-off-by: Johan Hovold <johan@kernel.org>

Thanks, applied.


Takashi