Re: [libvirt] [PATCH] conf: Fix parsing of seclabels without model

On 08/30/2012 03:03 PM, Daniel P. Berrange wrote: >On Thu, Aug 30, 2012 at 07:12:26PM +0200, Jiri Denemark wrote: >>On Thu, Aug 30, 2012 at 13:19:31 -0300, Marcelo Cerri wrote: >>>With this patch libvirt tries to assign a model to seclabels when model >>>is missing. Libvirt will look up at host's capabilities and assign a >>>model in order to each seclabel that doesn't have a model assigned. >>> >>>This patch fixes: >>> >>>1. The problem with existing guests that have a seclabel defined in its XML. >>>2. A XML parse error when a guest is restored. >>> >>>Signed-off-by: Marcelo Cerri <mhcerri(a)linux.vnet.ibm.com&gt; >>>--- >>> src/conf/domain_conf.c | 56 ++++++++++++++++++++++++++------------------------ >>> 1 file changed, 29 insertions(+), 27 deletions(-) >> >>I think this is trying to fix the issue at a wrong place. It's not that XML >>generated by older libvirtd is not correctly parsed by current libvirtd. The >>problem is that *current* libvirtd creates an XML that it cannot parse back. >>Thus we should rather fix the code that formats the XML. >> >>On that front, I'm concerned about migration compatibility of this new >>security driver code. If we just blindly emit <seclabel type='dynamic' >>model='dac' relabel='yes'> element into the XML, I'm pretty sure an older >>libvirtd will complain about it even though the element was not used to do >>anything special that would be done anyway (that is, if labels are the default >>qemu_user:qemu_group). > >Yes, we should not auto-add a <seclabel> for model=dac unless we have >configured it to auto-assign a private uid:gid pair per guest. If it is >operating in the mode where it just uses a fixed uid:gid pair we should >not emit the seclabel. > Can you explain which problem this auto-added <seclabel> for model=dac can create? I really can see a migration compatibility issue with it. When a <seclabel> for model=selinux is not defined for a guest, and SELinux driver is in use, a <seclabel> is also auto-added to this guest.