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Message-ID: <20110526185432.GB3476@elte.hu>
Date:	Thu, 26 May 2011 20:54:32 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Will Drewry <wad@...omium.org>, Colin Walters <walters@...bum.org>,
	Kees Cook <kees.cook@...onical.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	linux-kernel@...r.kernel.org, James Morris <jmorris@...ei.org>
Subject: Re: [PATCH 3/5] v2 seccomp_filters: Enable ftrace-based system call
 filtering


* Linus Torvalds <torvalds@...ux-foundation.org> wrote:

> And if you filter system calls, it's entirely possible that you can 
> attack suid executables through such a vector. Your "limit system 
> calls for security" security suddenly turned into "avoid the system 
> call that made things secure"!

That should not be possible with Will's event filter based solution 
(his last submitted patch), due to this code in fs/exec.c (which is 
in your upstream tree as well):

        /*
         * Flush performance counters when crossing a
         * security domain:
         */
        if (!get_dumpable(current->mm))
                perf_event_exit_task(current);

This will drop all filters if a setuid-root (or whatever setuid) 
binary is executed from a filtered environment.

Does this cover the case you were thinking of?

Thanks,

	Ingo
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