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From:   Johan Hovold <johan@kernel.org>
To:     Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc:     Mauro Carvalho Chehab <mchehab@kernel.org>,
        linux-media@vger.kernel.org, linux-usb@vger.kernel.org,
        linux-kernel@vger.kernel.org, Johan Hovold <johan@kernel.org>,
        stable@vger.kernel.org
Subject: [PATCH] media: uvcvideo: fix division by zero at stream start
Date:   Tue, 26 Oct 2021 11:55:11 +0200
Message-Id: <20211026095511.26673-1-johan@kernel.org>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

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