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

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Message-ID: <53C00D3C.7080808@zytor.com>
Date:	Fri, 11 Jul 2014 09:13:48 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Paul Moore <pmoore@...hat.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 07/11/2014 09:11 AM, Paul Moore wrote:
> 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).
> 

OK, that seems reasonable.

	-hpa

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