[Pkg-xen-devel] Bug#503046: xen-utils-3.2-1: inadequate error handling for the case of a failure to use a loopback device

[Russell Coker]

Package: xen-utils-3.2-1
Version: 3.2.1-2
Severity: normal

When a DomU is defined as using a file: device the loopback driver will
be used to make it appear to be a regular block device.  The loopback
driver will by default only support 8 nodes so this is a limited
resource.

http://etbe.coker.com.au/2008/10/22/kernel-issues-with-debian-xen-and-centos-kernels/

If there is a problem that prevents correctly allocating the block
device (see the above URL for a description of how I encountered it when
using a CentOS kernel) then it will not free the loop device.  When the
domain is destroyed with "xm destroy" it will leave the loopback device,
if you run that a few times (EG you have a script to restart DomU's on
error) then you run out of loopback devices for the system.

The error handling code needs to deal with this case.