From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <mingo@elte.hu>
Received: from mx3.mail.elte.hu (mx3.mail.elte.hu [157.181.1.138])
	(using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits))
	(Client did not present a certificate)
	by ozlabs.org (Postfix) with ESMTPS id 02E7FDDF9B
	for <linuxppc-dev@ozlabs.org>; Thu,  7 May 2009 08:14:33 +1000 (EST)
Date: Thu, 7 May 2009 00:13:19 +0200
From: Ingo Molnar <mingo@elte.hu>
To: Markus Gutschke =?utf-8?B?KOmhp+Wtn+WLpCk=?= <markus@google.com>
Subject: Re: [PATCH 2/2] x86-64: seccomp: fix 32/64 syscall hole
Message-ID: <20090506221319.GA11493@elte.hu>
References: <20090228030413.5B915FC3DA@magilla.sf.frob.com>
	<alpine.LFD.2.00.0902271932520.3111@localhost.localdomain>
	<alpine.LFD.2.00.0902271948570.3111@localhost.localdomain>
	<20090228072554.CFEA6FC3DA@magilla.sf.frob.com>
	<alpine.LFD.2.00.0902280916470.3111@localhost.localdomain>
	<904b25810905061146ged374f2se0afd24e9e3c1f06@mail.gmail.com>
	<20090506212913.GC4861@elte.hu>
	<904b25810905061446m73c42040nfff47c9b8950bcfa@mail.gmail.com>
	<20090506215450.GA9537@elte.hu>
	<904b25810905061508n6d9cb8dbg71de5b1e0332ede7@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
In-Reply-To: <904b25810905061508n6d9cb8dbg71de5b1e0332ede7@mail.gmail.com>
Cc: linux-mips@linux-mips.org, x86@kernel.org, linux-kernel@vger.kernel.org,
	linuxppc-dev@ozlabs.org, sparclinux@vger.kernel.org,
	Andrew Morton <akpm@linux-foundation.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	stable@kernel.org, Roland McGrath <roland@redhat.com>
List-Id: Linux on PowerPC Developers Mail List <linuxppc-dev.ozlabs.org>
List-Unsubscribe: <https://ozlabs.org/mailman/options/linuxppc-dev>,
	<mailto:linuxppc-dev-request@ozlabs.org?subject=unsubscribe>
List-Archive: <http://ozlabs.org/pipermail/linuxppc-dev>
List-Post: <mailto:linuxppc-dev@ozlabs.org>
List-Help: <mailto:linuxppc-dev-request@ozlabs.org?subject=help>
List-Subscribe: <https://ozlabs.org/mailman/listinfo/linuxppc-dev>,
	<mailto:linuxppc-dev-request@ozlabs.org?subject=subscribe>


* Markus Gutschke (顧孟勤) <markus@google.com> wrote:

> On Wed, May 6, 2009 at 14:54, Ingo Molnar <mingo@elte.hu> wrote:
> > Which other system calls would you like to use? Futexes might be
> > one, for fast synchronization primitives?
> 
> There are a large number of system calls that "normal" C/C++ code 
> uses quite frequently, and that are not security sensitive. A 
> typical example would be gettimeofday(). But there are other 
> system calls, where the sandbox would not really need to inspect 
> arguments as the call does not expose any exploitable interface.
> 
> It is currently awkward that in order to use seccomp we have to 
> intercept all system calls and provide alternative implementations 
> for them; whereas we really only care about a comparatively small 
> number of security critical operations that we need to restrict.
> 
> Also, any redirected system call ends up incurring at least two 
> context switches, which is needlessly expensive for the large 
> number of trivial system calls. We are quite happy that read() and 
> write(), which are quite important to us, do not incur this 
> penalty.

doing a (per arch) bitmap of harmless syscalls and replacing the 
mode1_syscalls[] check with that in kernel/seccomp.c would be a 
pretty reasonable extension. (.config controllable perhaps, for 
old-style-seccomp)

It would probably be faster than the current loop over 
mode1_syscalls[] as well.

	Ingo