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Date: Thu, 24 May 2012 20:55:09 -0500
From: Will Drewry <>
To: Andrew Morton <>
Subject: Re: [RFC PATCH 0/3] move the secure_computing call

On Thu, May 24, 2012 at 5:00 PM, Andrew Morton
<> wrote:
> On Thu, 24 May 2012 11:07:58 -0500
> Will Drewry <> 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 --

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.


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