[PATCH] media: uvcvideo: fix division by zero at stream start

Johan Hovold
2021-10-26T09:56:09Z

Add the missing bulk-endpoint max-packet sanity check to probe() to
avoid division by zero in uvc_alloc_urb_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: c0efd232929c ("V4L/DVB (8145a): USB Video Class driver")
Cc: stable@vger.kernel.org # 2.6.26
Signed-off-by: Johan Hovold <johan@kernel.org>
---
drivers/media/usb/uvc/uvc_video.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
index e16464606b14..85ac5c1081b6 100644
--- a/drivers/media/usb/uvc/uvc_video.c
+++ b/drivers/media/usb/uvc/uvc_video.c
@@ -1958,6 +1958,10 @@ static int uvc_video_start_transfer(struct uvc_streaming *stream,
if (ep == NULL)
return -EIO;

+ /* Reject broken descriptors. */
+ if (usb_endpoint_maxp(&ep->desc) == 0)
+ return -EIO;
+
ret = uvc_init_video_bulk(stream, ep, gfp_flags);
}

--
2.32.0