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

* Paul Davis <paul@linuxaudiosystems.com> wrote:

> Just a reminder: setuid root is precisely what we are attempting to
> avoid.
>
> >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
>
> This is insufficient, since they need to be able to drop RT scheduling
> and then reacquire it again later.

i believe RT-LSM provides a way to solve this cleanly: you can make your
audio app setguid-audio (note: NOT setuid), and make the audio group
have CAP_SYS_NICE-equivalent privilege via the RT-LSM, and then you
could have a finegrained per-app way of enabling SCHED_FIFO scheduling,
without giving _users_ the blanket permission to SCHED_FIFO. Ok?

this way if jackd (or a client) gets run by _any_ user, all jackd
processes will be part of the audio group and can do SCHED_FIFO - but
users are not automatically trusted with SCHED_FIFO.

you are currently using RT-LSM to enable a user to do SCHED_FIFO, right?
I think the above mechanism is more secure and more finegrained than
that.

Ingo
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