kernel-hardening - Re: [PATCH v2] futex: mark get_robust

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Message-ID: <CAFLxGvxXLoeaQFQwrBmaUpk6qHi2qn2piTCJ4atTcrg2UC7oAw@mail.gmail.com>
Date: Fri, 3 Aug 2012 13:30:31 +0200
From: richard -rw- weinberger <richard.weinberger@...il.com>
To: Cyrill Gorcunov <gorcunov@...nvz.org>
Cc: Pavel Emelyanov <xemul@...allels.com>, "Eric W. Biederman" <ebiederm@...ssion.com>, 
	Kees Cook <keescook@...omium.org>, Thomas Gleixner <tglx@...utronix.de>, linux-kernel@...r.kernel.org, 
	Randy Dunlap <rdunlap@...otime.net>, Darren Hart <dvhart@...ux.intel.com>, 
	Peter Zijlstra <a.p.zijlstra@...llo.nl>, Andrew Morton <akpm@...ux-foundation.org>, 
	Jiri Kosina <jkosina@...e.cz>, David Howells <dhowells@...hat.com>, 
	"Serge E. Hallyn" <serge.hallyn@...onical.com>, linux-doc@...r.kernel.org, 
	kernel-hardening@...ts.openwall.com, spender@...ecurity.net
Subject: Re: [PATCH v2] futex: mark get_robust_list as deprecated

On Fri, Aug 3, 2012 at 1:27 PM, Cyrill Gorcunov <gorcunov@...nvz.org> wrote:
> On Fri, Aug 03, 2012 at 01:19:24PM +0200, richard -rw- weinberger wrote:
>> >>
>> >> CRIU folks, how do you deal with futex robust lists?
>> >
>> > Well, I believe we were over-optimistic in claiming that we don't need this
>> > syscall (to be fair I think we simply yet not faced the problem Eric points).
>> > So we need some way to fetch this address and set it back. If get_robust_list
>> > get deprecated maybe we could print it out in /proc/pid/stat or something?
>>
>> Kees, you said get_robust_list() can be used to bypass ASLR.
>> How? What makes it worse than /proc/pid/maps?
>>
>> If the robust list address itself is bad, removing get_robust_list()
>> and putting the information into /proc is useless.
>
> Look, the /proc entry might check for some CAP and do not allow
> a regular user to fetch this address.

We could also add another check to get_robust_list().
It does already ptrace_may_access().

-- 
Thanks,
//richard

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