[HACKERS] semaphore usage "port based"?

[Marc G. Fournier]

On Tue, 4 Apr 2006, Peter Jeremy wrote:

> On Mon, 2006-Apr-03 08:19:00 -0400, Daniel Eischen wrote:
>> I don't really see what the problem is.  ESRCH seems perfectly
>> reasonable for trying to kill (even sig 0) a process from a
>> different jail.  If you're in a jail, then you shouldn't have
>> knowledge of processes from other jails.
>
> I agree in general.  The problem here is that SysV IPC isn't
> jail-aware - there's a single SysV IPC address space across the
> physical system.  This confuses (eg) postgres because it can
> see the SHM for a postgres instance in another jail but kill(2)
> claims that the process associated with that SHM doesn't exist.
>
> There appear to be two solutions:
> 1) Add a sysctl to change cr_cansignal() and/or prison_check() to
>   make processes visible between jails.
> 2) Change SysV IPC to be jail-aware.
>
> The former is trivial - but has a number of security implications.

And this is what is losing me ... what security implications does being 
able to kill(PID, 0) a process pose?  I can see allowing kill(PID, TERM) a 
process in another jail being a very bad thing, but if its just checking 
whether a PID is in use or not, isn't the security issue minimal?

----
Marc G. Fournier           Hub.Org Networking Services (http://www.hub.org)
Email: scrappy at hub.org           Yahoo!: yscrappy              ICQ: 7615664