Messages in this thread |  | | Date | Tue, 4 Oct 2016 15:18:40 -0500 | From | "Serge E. Hallyn" <> | Subject | Re: [RFC][PATCH 0/2] Another pass at Android style loosening of cgroup attach permissions |
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Quoting Tejun Heo (tj@kernel.org): > Hello, John. > > On Tue, Oct 04, 2016 at 11:01:12AM -0700, John Stultz wrote: > > So to make sure I understand your suggestion, you're suggesting the > > cgroupfs files like: > > cpuctrl/tasks, > > cpuctrl/bg_non_interactive/tasks, > > cpuset/foreground/tasks, > > cpuset/background/tasks, > > etc > > use ACL permissions to specify the specific uids that can write to > > them? I guess this would be conceptually similar to just setting the > > owner to the system task, no? Though I'm not sure that would be > > Yeah, finer grained but essentially just giving write perms. > > > sufficient since it would still fail the > > cgroup_procs_write_permission() checks. Or are you suggesting we add > > extra logic to make the file owner uid as sufficient to change other > > tasks? > > Hah, now I'm not sure how this is supposed to work inside a userns as > it's checking against GLOBAL_ROOT_UID. cc'ing Serge. Serge, can you > please have a look?
Hi, thanks for the cc,
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.
> But back on subject, yeah, I think a capability based approach is > better here too. No idea how difficult it is to add a new CAP but I > think it's worth trying. Can you please spin up a patch? > > Thanks! > > -- > tejun
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