Re: stacker and vm_enough_memory

From: Stephen Smalley (sds@private)
Date: Wed Jun 29 2005 - 06:32:41 PDT


On Tue, 2005-06-28 at 16:48 -0700, Tony Jones wrote:
> For stacker, if no module is registered, stacker_vm_enough_memory calls
> capable() rather than dummy_capable()  [but the problem would be the same
> if capability was the first module in the list (or any module who's
> vm_enough_memory hook called capable().]
> 
> The issue is that if any module in the chain tries to do any auditing based
> on rejecting capable() things get quite noisy.
> 
> I would imaging selinux auditing, if enabled, would see a similar problem.

I remember having this problem (spurious SELinux auditing of
CAP_SYS_ADMIN checks by vm_enough_memory) with earlier versions of
stacker, but it ultimately being fixed by Serge's other patches for
consolidating the vm_enough_memory hooks into a common helper that were
upstreamed earlier and the removal of the selinux_vm_enough_memory hook
by the stacking patches.  With stacker+SELinux+cap_stack, stacker should
end up calling cap_vm_enough_memory, which internally just calls
cap_capable(), so SELinux isn't involved at all in the computation.

Whether or not stacker should fall back to calling the top-level
capable() is unclear, but it isn't going to matter for most people, as
they will be stacking with dummy or capability or cap_stack, and thus
will have a vm_enough_memory hook defined (and none of those hooks call
the top-level capable internally anymore).
  
-- 
Stephen Smalley
National Security Agency



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