[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <20090506221319.GA11493@elte.hu>
Date: Thu, 7 May 2009 00:13:19 +0200
From: Ingo Molnar <mingo@...e.hu>
To: Markus Gutschke (顧孟勤) <markus@...gle.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>,
Roland McGrath <roland@...hat.com>,
Andrew Morton <akpm@...ux-foundation.org>, x86@...nel.org,
linux-kernel@...r.kernel.org, stable@...nel.org,
linux-mips@...ux-mips.org, sparclinux@...r.kernel.org,
linuxppc-dev@...abs.org
Subject: Re: [PATCH 2/2] x86-64: seccomp: fix 32/64 syscall hole
* Markus Gutschke (顧孟勤) <markus@...gle.com> wrote:
> On Wed, May 6, 2009 at 14:54, Ingo Molnar <mingo@...e.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
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists