[RFC] Syntax Proposal for Seccomp Filters in Upstart

[Steve Langasek]

On Tue, Dec 18, 2012 at 05:29:27PM +0100, David Gaarenstroom wrote:
> > Combined with the fact that, as mentioned, errno numeric values are not
> > portable across architectures, I think it's better to just prohibit them
> > outright rather than allow users to write jobs that will behave in
> > unexpected manners.

> I wouldn't advice using numeric values either, I'd only allow them as
> fall-back. James' concern seems to be that syscall numbers might be
> missing, and that might be just as much the case for errno numbers...
> If someone likes to use a numeric value he *must* have a very good
> reason for doing so and he should realize that that's
> risky/non-portable/hackish.

This simply is not as enforceable requirement.  If you make the facility
available, someone *will* use it for the wrong reasons, and create
gratuitously unportable jobs (which *misbehave* rather than fail when copied
between systems).

The way to make sure that people aren't using numeric errno or syscall
values without a good reason is to disallow it entirely in the first
implementation, and wait for someone to come to us with their problems. 
Then when we have *real* use cases rather than just theoretical ones, we can
try to solve them in a way that minimizes the risk of foot-shooting.

-- 
Steve Langasek                   Give me a lever long enough and a Free OS
Debian Developer                   to set it on, and I can move the world.
Ubuntu Developer                                    http://www.debian.org/
slangasek at ubuntu.com                                     vorlon at debian.org
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