linux-kernel - Re: [PATCH 2/3] [RFC] seccomp: give BPF x32 bit when restoring x32 filter

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Date:	Fri, 11 Jul 2014 12:11:37 -0400
From:	Paul Moore <pmoore@...hat.com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Richard Guy Briggs <rgb@...hat.com>, linux-audit@...hat.com,
	linux-kernel@...r.kernel.org, Eric Paris <eparis@...hat.com>,
	Al Viro <aviro@...hat.com>, Will Drewry <wad@...omium.org>
Subject: Re: [PATCH 2/3] [RFC] seccomp: give BPF x32 bit when restoring x32 filter

On Thursday, July 10, 2014 09:06:02 PM H. Peter Anvin wrote:
> Incidentally: do seccomp users know that on an x86-64 system you can
> recevie system calls from any of the x86 architectures, regardless of
> how the program is invoked?  (This is unusual, so normally denying those
> "alien" calls is the right thing to do.)

I obviously can't speak for all seccomp users, but libseccomp handles this by 
checking the seccomp_data->arch value at the start of the filter and killing 
(by default) any non-native architectures.  If you want, you can change this 
default behavior or add support for other architectures (e.g. create a filter 
that allows both x86-64 and x32 but disallows x86, or any combination of the 
three for that matter).

-- 
paul moore
security and virtualization @ redhat

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