linux-kernel - [PATCH 4.14 110/143] media: uvcvideo: Fix driver reference counting

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Message-Id: <20181102182906.624871582@linuxfoundation.org>
Date:   Fri,  2 Nov 2018 19:34:55 +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, Philipp Zabel <philipp.zabel@...il.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
        Sudip Mukherjee <sudipm.mukherjee@...il.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.14 110/143] media: uvcvideo: Fix driver reference counting

4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

commit f9ffcb0a21e1fa8e64d09ed613d884e054ae8191 upstream

kref_init initializes the reference count to 1, not 0. This additional
reference is never released since the conversion to reference counters.
As a result, uvc_delete is not called anymore when UVC cameras are
disconnected.
Fix this by adding an additional kref_put in uvc_disconnect and in the
probe error path. This also allows to remove the temporary additional
reference in uvc_unregister_video.

Fixes: 9d15cd958c17 ("media: uvcvideo: Convert from using an atomic variable to a reference count")

Signed-off-by: Philipp Zabel <philipp.zabel@...il.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@...nel.org>
Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@...il.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/media/usb/uvc/uvc_driver.c | 11 ++---------
 1 file changed, 2 insertions(+), 9 deletions(-)

diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c
index 6d22b22cb35b..064d88299adc 100644
--- a/drivers/media/usb/uvc/uvc_driver.c
+++ b/drivers/media/usb/uvc/uvc_driver.c
@@ -1865,13 +1865,6 @@ static void uvc_unregister_video(struct uvc_device *dev)
 {
 	struct uvc_streaming *stream;
 
-	/* Unregistering all video devices might result in uvc_delete() being
-	 * called from inside the loop if there's no open file handle. To avoid
-	 * that, increment the refcount before iterating over the streams and
-	 * decrement it when done.
-	 */
-	kref_get(&dev->ref);
-
 	list_for_each_entry(stream, &dev->streams, list) {
 		if (!video_is_registered(&stream->vdev))
 			continue;
@@ -1880,8 +1873,6 @@ static void uvc_unregister_video(struct uvc_device *dev)
 
 		uvc_debugfs_cleanup_stream(stream);
 	}
-
-	kref_put(&dev->ref, uvc_delete);
 }
 
 static int uvc_register_video(struct uvc_device *dev,
@@ -2129,6 +2120,7 @@ static int uvc_probe(struct usb_interface *intf,
 
 error:
 	uvc_unregister_video(dev);
+	kref_put(&dev->ref, uvc_delete);
 	return -ENODEV;
 }
 
@@ -2146,6 +2138,7 @@ static void uvc_disconnect(struct usb_interface *intf)
 		return;
 
 	uvc_unregister_video(dev);
+	kref_put(&dev->ref, uvc_delete);
 }
 
 static int uvc_suspend(struct usb_interface *intf, pm_message_t message)
-- 
2.17.1