Commit 9e68c539 authored Feb 16, 2015 by Laurent Pinchart Committed by Mauro Carvalho Chehab Apr 02, 2015

[media] uvcvideo: Don't call vb2 mmap and get_unmapped_area with queue lock held

videobuf2 has long been subject to AB-BA style deadlocks due to the
queue lock and mmap_sem being taken in different orders for the mmap and
get_unmapped_area operations. The problem has been fixed by making those
two operations callable without taking the queue lock, using an
mmap_lock internal to videobuf2.

The uvcvideo driver still calls the mmap and get_unmapped_area
operations with the queue lock held, resulting in a potential deadlock.
As the operations can now be called without locking the queue, fix it.

Reported-by: Bjørn Mork <bjorn@mork.no>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

parent cfa96722

drivers/media/usb/uvc/uvc_queue.c

+2 −13

Original line number	Diff line number	Diff line
		@@ -306,25 +306,14 @@ int uvc_queue_streamoff(struct uvc_video_queue *queue, enum v4l2_buf_type type)

		int uvc_queue_mmap(struct uvc_video_queue queue, struct vm_area_struct vma)
		{
		int ret;

		mutex_lock(&queue->mutex);
		ret = vb2_mmap(&queue->queue, vma);
		mutex_unlock(&queue->mutex);

		return ret;
		return vb2_mmap(&queue->queue, vma);
		}

		#ifndef CONFIG_MMU
		unsigned long uvc_queue_get_unmapped_area(struct uvc_video_queue *queue,
		unsigned long pgoff)
		{
		unsigned long ret;

		mutex_lock(&queue->mutex);
		ret = vb2_get_unmapped_area(&queue->queue, 0, 0, pgoff, 0);
		mutex_unlock(&queue->mutex);
		return ret;
		return vb2_get_unmapped_area(&queue->queue, 0, 0, pgoff, 0);
		}
		#endif