deleting vm is failed for lvm type

I am using the lvm function of nova-compute , It is successful when creating the vm, but failed when deleting it

the following is failed information:
File "/usr/lib/python2.6/site-packages/nova/compute/manager.py", line 869, in terminate_instance
  do_terminate_instance()
File "/usr/lib/python2.6/site-packages/nova/utils.py", line 679, in inner
  retval = f(*args, **kwargs)
File "/usr/lib/python2.6/site-packages/nova/compute/manager.py", line 862, in do_terminate_instance
  self._delete_instance(context, instance)
File "/usr/lib/python2.6/site-packages/nova/compute/manager.py", line 839, in _delete_instance
  self._shutdown_instance(context, instance)
File "/usr/lib/python2.6/site-packages/nova/compute/manager.py", line 804, in _shutdown_instance
  block_device_info)
File "/usr/lib/python2.6/site-packages/nova/virt/libvirt/driver.py", line 498, in destroy
  self._cleanup(instance, network_info, block_device_info)
File "/usr/lib/python2.6/site-packages/nova/virt/libvirt/driver.py", line 564, in _cleanup
  self._cleanup_lvm(instance)
File "/usr/lib/python2.6/site-packages/nova/virt/libvirt/driver.py", line 568, in _cleanup_lvm
  disks = self._lvm_disks(instance)
File "/usr/lib/python2.6/site-packages/nova/virt/libvirt/driver.py", line 586, in _lvm_disks
  disk_names = filter(belongs_to_instance, os.listdir(vg))
Error: [Errno 13] Permission denied: '/dev/xenvg1'

this error show that nova-compute process whch runned in nova user has not Permission for vgs directory /dev/xenvg1

# ls -l /dev/
drwx------ 2 root root 80 Aug 28 17:13 xenvg1

Can I must use the chmod command to change the permission of vg directory ?
 I think this problem may be one bug ,because creating vg ,the default permission is drwx------

my nova.conf about lvm :

libvirt_images_type=lvm
libvirt_images_volume_group=xenvg1