Re: sys_setpriority error

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Reply: Titus D. Winters: "Re: sys_setpriority error"
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chrisat_private

* Titus D. Winters (titusat_private) wrote:

> > The dummy functions don't really provide much in the way of security.  They
> > fall some where between DAC and everybody is root.  Stephen Smalley has
> > suggested re-evaluating the dummy code and adding root checks to align with
> > DAC.  I am inclined to fix this in dummy_setnice rather than
> > sys_setpriority.
> 
> I think the issue is that the logic is wrong (or unclear at the least.)
> 
> Currently it is saying:
> if (you are rootish, own the process, or the module lets you) you can
> renice things
> 
> And Roy suggests:
> if ((you are rootish or own the process) AND (the module lets you)) you
> can renice things.
> 
> Beyond even dummy stuff, it seems more useful (not to mention safer) to
> rework the logic.  This way one could write modules that would hamper root
> (useful for trappin' baddies), instead of writing modules that allow huge
> security holes.

I understand what your driving at.  But I hesitate to make logic changes to
the kernel.  Consider original code reads...

  if (p->uid != current->euid &&
     p->uid != current->uid && !capable(CAP_SYS_NICE)) {

This really doesn't have any test for root.  just checks that both your uid
and euid don't match the target process's uid _and_ you aren't capable.

-chris

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