[Devel] Re: [PATCH 0/3] capabilities: per-process capbset

[Serge E. Hallyn]

Quoting Serge E. Hallyn (serue at us.ibm.com):
> Here is a new per-process capability bounding set patchset
> which I expect to send to linux-kernel soon.  It makes
> the capbset per-process.  A process can only permanently
> remove bits from it's bounding set, not add them.  To
> remove bits, CAP_SYS_ADMIN is currently needed.  Maybe
> that's not the best choice, but some privilege should
> probably be required.
> 
> The intent is to allow a process tree to start with
> certain capabilities, i.e. CAP_MKNOD, permanently
> removed, so that running a setuid binary or one with
> file capabilities will still not result in those
> capabilities.  The immediate use case for this is
> containers/virtual servers.
> 
> I am not taking the task_capability_lock during
> cap_prctl_setbset(), just as it is not taken when
> capabilities are calculated during fork.  That means

Where by fork I of course mean exec.

-serge

> it can race with another task doing capsetp() on it,
> and with capgetp().  I'm still looking for comments
> on whether the fix I sent out last week is correct.
> If it is, then I'll take the task_capability_lock
> during cap_prctl_setbset().
> 
> thanks,
> -serge
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