linux-kernel - Re: [PATCH v2] kernel: Conditionally support non-root users, groups and capabilities

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Date:	Fri, 30 Jan 2015 11:13:02 -0800
From:	josh@...htriplett.org
To:	Casey Schaufler <casey@...aufler-ca.com>
Cc:	paulmck@...ux.vnet.ibm.com, Iulia Manda <iulia.manda21@...il.com>,
	gnomes@...rguk.ukuu.org.uk, serge.hallyn@...onical.com,
	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	peterz@...radead.org, mhocko@...e.cz,
	LSM <linux-security-module@...r.kernel.org>
Subject: Re: [PATCH v2] kernel: Conditionally support non-root users,
 groups and capabilities

On Thu, Jan 29, 2015 at 06:25:23PM -0800, Casey Schaufler wrote:
> On 1/29/2015 5:36 PM, Paul E. McKenney wrote:
> > A few K here, a few K there, and pretty soon you actually fit into the
> > small-memory 32-bit SoCs.  I do not believe that the processing time
> > is the issue.
> 
> And UNIX, with UID and GID processing, used to run in 64K of RAM,
> without swap or paging. Bluntly, there are many other places to look
> before you go here.

And we're looking in all those places too.  Each patch is worth
evaluating independently.  We've *already* gone here, the code is
written (and being revised based on feedback), and "go work over there
out of my backyard" is not going to work.  One of these days, we're
going to run in 64k again.

> >> As for LSMs, I can easily see putting in the security model from the old
> >> RTOS on top of a NON_ROOT configuration. Won't that be fun when the CVEs
> >> start to fly?

The security model is "there's one process on this system".  (Expect
patches for CONFIG_FORK=n and CONFIG_EXEC=n at some point.)

> >> Do you think you'll be running system services like systemd on top of this?
> >> Anyone *else* remember what happened when they put capability handling into
> >> sendmail?
> > Nope, I don't expect these systems to be using LSM, systemd, or sendmail.
> > I think that many of these will instead run the application directly
> > out of the init process.
> 
> Where an "application" might be something like CrossWalk,

No, not a chance.  If you're running a web runtime, you're on a much
larger system, and you're going to be less concerned about shaving
kilobytes; you're also going to want many of the kernel facilities for
sandboxing code.

The kinds of applications we're talking about here run entirely in one
binary, serving a few very narrow functions.  We're not talking
"automobile IVI system" here; we're talking "two buttons and an output",
or "a few sensors and an SD card".

- Josh Triplett
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