[kernel-hardening] Re: [RFC] ipc: introduce shm_rmid_forced sysctl

[Ingo Molnar <mingo@elte.hu>]

* Vasiliy Kulikov <segoon@openwall.com> wrote:

> On Fri, Jul 01, 2011 at 13:25 +0200, Ingo Molnar wrote:
> > Furthermore, if testing shows that this is not actually breaking 
> > anything in a serious way we could also in theory simplify the patch 
> > and just make this the default behavior with no runtime ability to 
> > switch it off.
> 
> I'm afraid it's impossible.  From -ow readme:
> 
> "Of course, this breaks the way things are defined, so some 
> applications might stop working. In particular, expect most 
> commercial databases to break. Apache and PostgreSQL are known to 
> work, though. :-)"
> 
> http://www.openwall.com/linux/README.shtml
> 
> But as it was written in days of Linux 2.4.x, the situation could 
> have changed.  A desktop system seems to work.

As we really prefer working systems over non-working ones (and lots 
of unattached shm segments can clearly result in a non-working 
system) we can only accept the "this will break stuff" argument if 
it's *demonstrated* to break stuff and if the failure scenario is 
carefully described in the commit.

It would take a serious breakage to override a "system locks up 
swapping itself to death" failure scenario.

Thanks,

	Ingo