Re: libcap vs libcap-ng mess

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Paolo Bonzini (pbonzini@redhat.com) wrote:
> On 29/11/19 10:34, Daniel P. Berrangé wrote:
> >>   y) Should we flip over to only using one or the other - what
> >>      are the advantages?
> > In libvirt we use libcap-ng. We picked this originally as its API
> > design allows you do write simpler code than libcap in some cases
> > You can see some docs & examples here:
> > 
> >   https://people.redhat.com/sgrubb/libcap-ng/
> > 
> > So I vote for changing the 9p code to use libcap-ng.
> 
> It's not entirely trivial because fsdev-proxy-helper wants to keep the
> effective set and clear the permitted set; in libcap-ng you can only
> apply both sets at once, and you cannot choose only one of them in
> capng_clear/capng_get_caps_process.  But it's doable, I'll take a look.

I'm having some difficulties making the same conversion for virtiofsd;
all it wants to do is drop (and later recover) CAP_FSETID
from it's effective set;  so I'm calling capng_get_caps_process
(it used to be cap_get_proc).  While libcap survives just using the
capget syscall, libcap-ng wants to read /proc/<TID>/status - and
that's a problem because we're in a sandbox without /proc mounted
at that point.

Dave

> In the meanwhile, if someone else wants to look at the CI I would
> appreciate that.
> 
> Paolo
> 
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK