Notify special task kill using wait* functions

[Andi Kleen]

> > Any caching of state is inherently insecure because any caches of limited
> > size can be always thrashed by a purposeful attacker. I suppose the
> > only thing that would work is to actually write something to the
> > executable itself on disk, but of course that doesn't always work either.
> 
> I'm also working on this. In the next version I will try to find a way to
> prevent brute force attacks through the execve system call with more than
> one level of forking.

Thanks.

Thinking more about it what I wrote above wasn't quite right. The cache
would only need to be as big as the number of attackable services/suid
binaries. Presumably on many production systems that's rather small,
so a cache (which wouldn't actually be a cache, but a complete database)
might actually work.

-Andi