Commit 69c0e9c5 authored Nov 01, 2014 by Laurent Pinchart Committed by Mauro Carvalho Chehab Dec 04, 2014

[media] v4l: vb2: Fix race condition in _vb2_fop_release



The function releases the queue if the file being released is the queue
owner. The check reads the queue->owner field without taking the queue
lock, creating a race condition with functions that set the queue owner,
such as vb2_ioctl_reqbufs() for instance.

Fix this by moving the queue->owner check within the mutex protected
section.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Acked-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

parent f6cee188

drivers/media/v4l2-core/videobuf2-core.c

+4 −4

Original line number	Diff line number	Diff line
		@@ -3389,14 +3389,14 @@ int _vb2_fop_release(struct file file, struct mutex lock)
		{
		struct video_device *vdev = video_devdata(file);

		if (file->private_data == vdev->queue->owner) {
		if (lock)
		mutex_lock(lock);
		if (file->private_data == vdev->queue->owner) {
		vb2_queue_release(vdev->queue);
		vdev->queue->owner = NULL;
		}
		if (lock)
		mutex_unlock(lock);
		}
		return v4l2_fh_release(file);
		}
		EXPORT_SYMBOL_GPL(_vb2_fop_release);