[git:media_stage/master] media: uvcvideo: fix division by zero at stream start

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Subject: media: uvcvideo: fix division by zero at stream start
Author:  Johan Hovold <johan@xxxxxxxxxx>
Date:    Tue Oct 26 11:55:11 2021 +0200

Add the missing bulk-endpoint max-packet sanity check to
uvc_video_start_transfer() 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@xxxxxxxxxxxxxxx      # 2.6.26
Signed-off-by: Johan Hovold <johan@xxxxxxxxxx>
Reviewed-by: Kieran Bingham <kieran.bingham+renesas@xxxxxxxxxxxxxxxx>
Signed-off-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@xxxxxxxxxx>

 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 9f37eaf28ce7..1b4cc934109e 100644
--- a/drivers/media/usb/uvc/uvc_video.c
+++ b/drivers/media/usb/uvc/uvc_video.c
@@ -1963,6 +1963,10 @@ 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);
 	}
 



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