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Re: [libvirt] [PATCH] Fix a compilation problem with LXC drop capabilities



On Fri, May 29, 2009 at 04:42:54PM -0500, Serge E. Hallyn wrote:
> Quoting Ryota Ozaki (ozaki ryota gmail com):
> > On Fri, May 29, 2009 at 9:20 PM, Daniel Veillard <veillard redhat com> wrote:
> > >  The lxcContainerDropCapabilities() function requires PR_CAPBSET_DROP
> > > to be defined in order to compile, but it may not be defined in older
> > > kernels. So I made the compilation of the core of the function
> > > conditional, raise an error but still return 0 to not make the
> > > container initialization fail. But I'm unsure, should we just fail and
> > > return -1 if we can't drop capabilities instead ?
> > 
> > I think it depends on applications. AFAIK, libvirt intends to support
> > two types of applications; application workload isolation and
> > virtual private servers. In the latter case, we MUST drop the capability
> > and if it fails we have to fail booting a container as well. OTOH, in
> > the former case, we might not need to fail booting.
> > 
> > Nonetheless, I agree with the patch because old kernels that don't
> > support PR_CAPBSET_DROP (they would be 2.6.24 or earlier) don't
> > have enough facilities to support VPSs (e.g., they lacks sysfs, devpts, etc.).
> > Therefore, with the old kernels we don't need to care much about the
> > dropping-failed-but-booting-success case.
> 
> Hmm, yeah but note that often userspace is out of date with respect to
> "recent" new kernel-related defines.  I do a lot of testing on a rhel
> 5.3 partition with spanking-new kernels, so rare is the time that I
> don't have to do
> 
> #ifndef PR_CAPBSET_DROP
> #define PR_CAPBSET_DROP 24
> #endif
> 
> and same for clone flags (CLONE_NEWIPC), securebits, capabilities,
> etc.
> 
> So if the prctl(PR_CAPBSET_DROP) returns -ENOSYS then absolutely I
> agree, but the patch just does
> 
> #ifdef PR_CAPBSET_DROP
> 
> which seems wrong.

  Well, if you have a better patch to suggest, fire :-)

Daniel

-- 
Daniel Veillard      | libxml Gnome XML XSLT toolkit  http://xmlsoft.org/
daniel veillard com  | Rpmfind RPM search engine http://rpmfind.net/
http://veillard.com/ | virtualization library  http://libvirt.org/


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