[HACKERS] semaphore usage "port based"?

[Robert Watson]

On Mon, 3 Apr 2006, Marc G. Fournier wrote:

> This falls under "well,we broke kill() so that it now reports a PID is not 
> in use even though it is, so its has to be the application that fixes it" 
> ... and you *still* haven't shown *why* kill() reporting a PID is in use, 
> even if its not in the current jail, is such a security threat ...

It is an issue of completeness and consistency.  We implement a single set of 
access control checks between processes, and try to avoid exceptions to them. 
This is one of my largest architectural gripes about access control in 4.x, 
actually: everywhere you look, the same "check" is implemented differently. 
Sometimes signal checks are done way, other times, other ways.  Likewise, 
debugging, monitoring, etc.  In 5.x forward, we use a centralized set of 
access control checks in order to provide consistent, reliable, and easy to 
analyze policy.  The more exceptions we introduced, the further we get from 
that goal.

Robert N M Watson