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Re: [libvirt] unable to set security context (NFSv4 problem?)



On Thu, 15 Apr 2010, Spencer Shimko wrote:

> Harald Dunkel wrote:
> > Hi folks,
> > 
> > Since I have moved the image file of a domain to an NFS
> > partition I get an error message at start time:
> > 
> > # virsh start mydomain
> > error: Failed to start domain mydomain
> > error: unable to set security context '110:140' on
> > '/storage/mydomain/vda.img': Invalid argument
> 
> What is security_driver set to in /etc/libvirt/qemu.conf?
> 
> It appears to be the security driver trying to update the security context
> stored on the filesystem as an extended attribute.  The NFS v4 filesystem
> currently lacks extended attribute support.  Without extended attributes there
> isn't a place to store the security context associated with the image file,
> hence the error.
> 
> I've CC'd James Morris who, in addition to working on the original libvirt
> security driver implementation, happens to be spearheading the NFS xattr
> support.  Hopefully he can provide some more information.

For NFSv4, we're working on adding security labeling directly to the 
protocol (local SELinux xattrs will be transported with this new 
protocol).  The IETF process is slowing it down significantly.

Because of this, I'm adding a simple xattr protocol to NFSv3, which should 
allow for server storage/retrieval of SELinux labels (but without 
security enforcement on the server).  Currently trying to get some 
technical issues agreed upon upstream and also now wiring up SELinux to 
the current code.  We're hoping to see this in RHEL 6.x.



 > 
> > 
> > The /storage partition is mounted with these options:
> > 
> > # cat /proc/mounts  | grep /storage
> > nasl002:/storage/ /storage nfs4
> > rw,relatime,vers=4,rsize=1048576,wsize=1048576,namlen=255,hard,proto=tcp,port=0,timeo=600,retrans=2,sec=sys,clientaddr=172.19.96.31,addr=172.19.96.213
> > 0 0
> > 
> > If I use a local disk instead, then there is no such
> > problem.
> 
> The fact that it works on local disk is likely attributable to the local
> filesystem supporting extended attributes.  Examples of these filesystems
> include ext2/3/4 and xfs.
> 
> > 
> > libvirt is version 0.7.7-4, as included with Debian.
> > Any helpful comment would be highly appreciated.
> 
> Out of curiosity, are you using the SELinux support in Debian?
> 
> --Spencer
> > 
> > 
> > Regards
> > 
> > Harri
> > 
> 

-- 
James Morris
<jmorris redhat com>


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