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Date: Thu, 24 May 2012 20:55:09 -0500
From: Will Drewry <wad@...omium.org>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org, mcgrathr@...gle.com, hpa@...or.com, 
	indan@....nu, netdev@...isplace.org, linux-security-module@...r.kernel.org, 
	kernel-hardening@...ts.openwall.com, mingo@...hat.com, oleg@...hat.com, 
	peterz@...radead.org, rdunlap@...otime.net, tglx@...utronix.de, luto@....edu, 
	serge.hallyn@...onical.com, pmoore@...hat.com, corbet@....net, 
	markus@...omium.org, coreyb@...ux.vnet.ibm.com, keescook@...omium.org, 
	viro@...iv.linux.org.uk, jmorris@...ei.org
Subject: Re: [RFC PATCH 0/3] move the secure_computing call

On Thu, May 24, 2012 at 5:00 PM, Andrew Morton
<akpm@...ux-foundation.org> wrote:
> On Thu, 24 May 2012 11:07:58 -0500
> Will Drewry <wad@...omium.org> wrote:
>
>> This is an RFC based on the comments from Al Viro and Eric Paris
>> regarding ptrace()rs being able to change the system call the kernel
>> sees after the seccomp enforcement has occurred (for mode 1 or 2).
>
> Perhaps you could repeat those comments in this changelog.

Oops :)  Here's the context -- https://lkml.org/lkml/2012/5/21/326

I doubt there's need for a repost though.

>> With this series applied, a (p)tracer of a process with seccomp enabled
>> will be unable to change the tracee's system call number after the
>> secure computing check has been performed.
>>
>> The x86 change is tested, as is the seccomp.c change.  For other arches,
>> it is not (RFC :).  Given that there are other inconsistencies in this
>> code across architectures, I'm not sure if it makes sense to attempt to
>> fix them all at once or to roll through as I attempt to add seccomp
>> filter support.
>>
>> As is, the biggest benefit of this change is just setting consistent
>> expectations in what the ptrace/seccomp interactions should be.  The
>> current ability for ptrace to "bypass" secure computing (by remapping
>> allowed system calls) is not necessarily a problem, but it is not
>> necessarily intuitive behavior.
>>
>
> Because my take on the above reasoning is "why did you bother writing
> these patches"!

Just to be thorough -- I wanted to make sure the discussion was framed
against actual code just in case I was missing something.  Otherwise,
I'd be happy to see these patches disappear into the annals of the
wayback machine.

thanks!

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