linux-kernel - Re: request_module vs. modprobe blacklist (and security subsystem implications)

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Date:	Sat, 24 Oct 2009 01:29:52 +1030
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Eric Paris <eparis@...hat.com>
Cc:	Alan Jenkins <sourcejedi.lkml@...glemail.com>,
	linux-kernel@...r.kernel.org, arjan@...radead.org,
	randy.dunlap@...cle.com, andi@...stfloor.org, dhowells@...hat.com,
	akpm@...ux-foundation.org
Subject: Re: request_module vs. modprobe blacklist (and security subsystem implications)

On Sat, 24 Oct 2009 12:53:50 am Eric Paris wrote:
> On Fri, 2009-10-23 at 19:46 +1030, Rusty Russell wrote:
> > On Fri, 23 Oct 2009 01:00:22 am Eric Paris wrote:
> > > > If a userspace program tries some security exploit that has been closed, do
> > > > you want to warn about it?  Because that seems to be the question here.
> > > 
> > > I say yes.  Knowing that malicious activity is taking place, even if it
> > > didn't hurt anything is useful.
> > 
> > Hi Eric,
> > 
> > Your proposal is troubling for three reasons:
> > 
> > 1) You would disable logging for things you actually want logged.
> 
> I would?

Yep, admin disables loading of ipx to prevent hole.  Now, you no longer get
logging notification.

> > 2) What *actually* happens when ssh tries to load ipv6 is that
> >    "modprobe net-pf-10" gets called.
> > 3) Containing modprobe behavior in one set of config files is really nice.
> 
> It is it also means that we, somewhat regularly call userspace
> needlessly and there is nothing an admin can do to stop it.

Yes, but that's nothing to do with SELinux; we exec modprobe for no effect.
Yet I've yet to see a report that this is a performance issue.  These brains
are in userspace for a reason.

> But it appears you disagree that fixing that problem is worth it, and I
> don't feel strongly enough to keep arguing  :)

But we have learnt something, at least!

Cheers,
Rusty.
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