Re: [RFC][PATCH 0/2] Another pass at Android style loosening of cgroup attach permissions

[Serge E. Hallyn]

Quoting Tejun Heo (tj@xxxxxxxxxx):
> Hello, Serge.
> 
> On Tue, Oct 04, 2016 at 03:18:40PM -0500, Serge E. Hallyn wrote:
> > how about changing the GLOBAL_ROOT_UID check with a targeted
> > capability check, like
> > 
> > 	if (!ns_capable(tcred->user_ns, CAP_SYS_NICE) &&
> >             !uid_eq(cred->euid, tcred->uid) &&
> >             !uid_eq(cred->euid, tcred->suid))
> > 		ret = -EACCES;
> > 
> > where the actual capability to use may require some thought.
> 
> Yeah, that's the direction I'm thinking too.  We can't use
> CAP_SYS_NICE in general tho.  Let's see if a dedicated CAP sticks.

One possibility would be to let each cgroup subsystem define
a move_caps capability mask which is required over the target
task.  And add a new CAP_CGROUP which always suffices?