Re: [patch, 2.6.11-rc2] sched: RLIMIT_RT_CPU_RATIO feature

[Jack O'Quin]

Peter Williams <pwil3058@xxxxxxxxxxxxxx> writes:

>>> If you have the source code for the programs then they could be
>>> modified to drop the root euid after they've changed policy.  Or
>>> even do the

> Paul Davis wrote:
>> This is insufficient, since they need to be able to drop RT
>> scheduling and then reacquire it again later.

> I believe that there are mechanisms that allow this.  The setuid man
> page states that a process with non root real uid but setuid as root
> can use the seteuid call to use the _POSIX_SAVED_IDS mechanism to
> drop and regain root privileges as required.

Which every system cracker knows.  Any attack on such a program is
going to re-acquire root privileges and take over the system.

Temporarily dropping privileges gains no security whatsoever.  It is
nothing more than a coding convenience.  The program remains *inside*
the system security perimeter.
-- 
  joq
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