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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        syzbot+c86454eb3af9e8a4da20@syzkaller.appspotmail.com,
        Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
        Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Subject: [PATCH 4.14 192/211] media: uvcvideo: Fix error path in control parsing failure
Date:   Wed, 27 Nov 2019 21:32:05 +0100
Message-Id: <20191127203111.818712853@linuxfoundation.org>
In-Reply-To: <20191127203049.431810767@linuxfoundation.org>
References: <20191127203049.431810767@linuxfoundation.org>
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From: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

commit 8c279e9394cade640ed86ec6c6645a0e7df5e0b6 upstream.

When parsing the UVC control descriptors fails, the error path tries to
cleanup a media device that hasn't been initialised, potentially
resulting in a crash. Fix this by initialising the media device before
the error handling path can be reached.

Fixes: 5a254d751e52 ("[media] uvcvideo: Register a v4l2_device")
Reported-by: syzbot+c86454eb3af9e8a4da20@syzkaller.appspotmail.com
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/media/usb/uvc/uvc_driver.c |   28 +++++++++++++++-------------
 1 file changed, 15 insertions(+), 13 deletions(-)

--- a/drivers/media/usb/uvc/uvc_driver.c
+++ b/drivers/media/usb/uvc/uvc_driver.c
@@ -2059,6 +2059,20 @@ static int uvc_probe(struct usb_interfac
 			   sizeof(dev->name) - len);
 	}
 
+	/* Initialize the media device. */
+#ifdef CONFIG_MEDIA_CONTROLLER
+	dev->mdev.dev = &intf->dev;
+	strscpy(dev->mdev.model, dev->name, sizeof(dev->mdev.model));
+	if (udev->serial)
+		strscpy(dev->mdev.serial, udev->serial,
+			sizeof(dev->mdev.serial));
+	usb_make_path(udev, dev->mdev.bus_info, sizeof(dev->mdev.bus_info));
+	dev->mdev.hw_revision = le16_to_cpu(udev->descriptor.bcdDevice);
+	media_device_init(&dev->mdev);
+
+	dev->vdev.mdev = &dev->mdev;
+#endif
+
 	/* Parse the Video Class control descriptor. */
 	if (uvc_parse_control(dev) < 0) {
 		uvc_trace(UVC_TRACE_PROBE, "Unable to parse UVC "
@@ -2079,19 +2093,7 @@ static int uvc_probe(struct usb_interfac
 			"linux-uvc-devel mailing list.\n");
 	}
 
-	/* Initialize the media device and register the V4L2 device. */
-#ifdef CONFIG_MEDIA_CONTROLLER
-	dev->mdev.dev = &intf->dev;
-	strlcpy(dev->mdev.model, dev->name, sizeof(dev->mdev.model));
-	if (udev->serial)
-		strlcpy(dev->mdev.serial, udev->serial,
-			sizeof(dev->mdev.serial));
-	strcpy(dev->mdev.bus_info, udev->devpath);
-	dev->mdev.hw_revision = le16_to_cpu(udev->descriptor.bcdDevice);
-	media_device_init(&dev->mdev);
-
-	dev->vdev.mdev = &dev->mdev;
-#endif
+	/* Register the V4L2 device. */
 	if (v4l2_device_register(&intf->dev, &dev->vdev) < 0)
 		goto error;