Re: FW: jackd/ audio apps mini policy
On 7 Nov 2003, Jack O'Quin wrote:
> Zenaan Harkness <zen@aaroncommercial.com> writes:
>
> > From: Matthias Urlichs
> > > Hi, Jack O'Quin wrote:
> > >
> > > > So far, no one is sure why CAP_SYS_RESOURCE is needed, but we find
> > > > that mlockall() fails without it.
> > >
> > > For good reason. The resource in question is physical memory. You could
> > > lock all the free memory with this program (thereby condemning it to swap
> > > death) if you're not VERY careful.
>
> Who is Matthias Urlichs? Has he not been following this discussion?
>
> Is he able to do anything about this mess? How can we contact him?
>From reading these comments and taking a look at the mlockall call and
how it is used in jack, I understand that this might really be
very dangerous ... mlockall (MCL_CURRENT | MCL_FUTURE)
anyone tried without CAP_SYS_RESOURCE , memory preallocation (I think this
would mean a maximum amount of jack clients) and without the "MCL_FUTURE".
Seems that the MCL_FUTURE would take up all memory and never give it free
at some point, hence it needs higher privileges.
(just a guess, ... again ...)
As it is now a user can lock up the machine by introducing (lots?) of
clients.
Guenter
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