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Date: Wed, 22 Feb 2012 14:23:46 +0000
From: Ben Hutchings <bhutchings@...arflare.com>
To: Indan Zupancic <indan@....nu>
CC: Will Drewry <wad@...omium.org>, <linux-kernel@...r.kernel.org>,
<linux-arch@...r.kernel.org>, <linux-doc@...r.kernel.org>,
<kernel-hardening@...ts.openwall.com>, <netdev@...r.kernel.org>,
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<rdunlap@...otime.net>, <mcgrathr@...omium.org>, <tglx@...utronix.de>,
<luto@....edu>, <eparis@...hat.com>, <serge.hallyn@...onical.com>,
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<markus@...omium.org>, <keescook@...omium.org>
Subject: Re: [PATCH v10 05/11] seccomp: add system call filtering using BPF
On Wed, 2012-02-22 at 09:19 +0100, Indan Zupancic wrote:
[...]
> Alternative approach: Tell the arch at filter install time and only run the
> filters with the same arch as the current system call. If no filters are run,
> deny the systemcall.
>
> Advantages:
>
> - Filters don't have to check the arch every syscall entry.
>
> - Secure by default. Filters don't have to do anything arch specific to
> be secure, no surprises possible.
>
> - If a new arch comes into existence, there is no chance of old filters
> becoming buggy and insecure. This is especially true for archs that
> had only one mode, but added another one later on: Old filters had no
> need to check the mode at all.
[...]
What about when there are multiple layers of restrictions? So long as
any one layer covers the new architecture, there is no default-deny even
though the other layers might not cover it.
I would have thought the way to make sure the architecture is always
checked is to pack it together with the syscall number.
Ben.
--
Ben Hutchings, Staff Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.
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