Re: Resource limits

[Al Boldi <a1426z@gawab.com>]

Neil Horman wrote:
> On Mon, Sep 26, 2005 at 08:32:14PM +0300, Al Boldi wrote:
> > Neil Horman wrote:
> > > On Mon, Sep 26, 2005 at 05:18:17PM +0300, Al Boldi wrote:
> > > > Rik van Riel wrote:
> > > > > On Sun, 25 Sep 2005, Al Boldi wrote:
> > > > > > Too many process forks and your system may crash.
> > > > > > This can be capped with threads-max, but may lead you into a
> > > > > > lock-out.
> > > > > >
> > > > > > What is needed is a soft, hard, and a special emergency limit
> > > > > > that would allow you to use the resource for a limited time to
> > > > > > circumvent a lock-out.
> > > > >
> > > > > How would you reclaim the resource after that limited time is
> > > > > over ?  Kill processes?
> > > >
> > > > That's one way,  but really, the issue needs some deep thought.
> > > > Leaving Linux exposed to a lock-out is rather frightening.
> > >
> > > What exactly is it that you're worried about here?
> >
> > Think about a DoS attack.
>
> Be more specific.  Are you talking about a fork bomb, a ICMP flood, what?

How would you deal with a situation where the system hit the threads-max 
ceiling?

> preventing resource starvation/exhaustion is often handled in a way thats
> dovetailed to the semantics of how that resources is allocated (i.e. you
> prevent syn-flood attacks differently than you manage excessive disk
> usage).

The issue here is a general lack of proper kernel support for resource 
limits.  The fork problem is just an example.

Thanks!

--
Al