Subject: Re: [PATCH 3/5] v2 seccomp_filters: Enable ftrace-based system call filtering

From: Ingo Molnar <[email-masked]>
Date: Tue, 17 May 2011 14:57:00 +0200

* Will Drewry <[email-masked]> wrote:

> > This is *far* more generic still yields the same short-term end result as 
> > far as your sandboxing is concerned.
> 
> Almost :/ [...]

Hey that's a pretty good result from a subsystem that was not written with your 
usecase in mind *at all* ;-)

> [...]  I still need to review the code you've pointed out, but, at present, 
> the ftrace hooks occur after the seccomp and syscall auditing hooks.  This 
> means that that code is exposed no matter what in this model.  To trim the 
> exposed surface to userspace, we really need those early hooks.  While I can 
> see both hacky and less hacky approaches around this, it stills strikes me 
> that the seccomp thread flag and early interception are good to reuse.  One 
> option might be to allow seccomp to be a secure-syscall event source, but I 
> suspect that lands more on the hack-y side of the fence :)

Agreed, there should be no security compromise imposed on your usecase, at all.

You could move the event callback sooner into the syscall-entry sequence to 
make sure it's the highest priority thing to process?

There's no semantic dependency on its current location so this can be changed 
AFAICS.

Thanks,

	Ingo