linux-kernel - [PATCH 5.15 14/28] media: uvcvideo: fix division by zero at stream start

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Date:   Tue, 18 Jan 2022 17:06:00 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Johan Hovold <johan@...nel.org>,
        Kieran Bingham <kieran.bingham+renesas@...asonboard.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
Subject: [PATCH 5.15 14/28] media: uvcvideo: fix division by zero at stream start

From: Johan Hovold <johan@...nel.org>

commit 8aa637bf6d70d2fb2ad4d708d8b9dd02b1c095df upstream.

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@...r.kernel.org      # 2.6.26
Signed-off-by: Johan Hovold <johan@...nel.org>
Reviewed-by: Kieran Bingham <kieran.bingham+renesas@...asonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/media/usb/uvc/uvc_video.c |    4 ++++
 1 file changed, 4 insertions(+)

--- 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(stru
 		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);
 	}