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

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Date:	Fri, 3 Aug 2012 13:19:24 +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 1:02 PM, Cyrill Gorcunov <gorcunov@...nvz.org> wrote:
>> >> I'm using this system call in an application and noticed that's marked
>> >> as deprecated now.
>> >> My application collects all kind of information from crashing programs.
>> >> It's installed in /proc/sys/kernel/core_pattern.
>> >>
>> >> If program X is crashing it executes get_robust_list(X) to get the
>> >> address of the robust list
>> >> and reads the list from /proc/X/mem.
>> >>
>> >> Is there another way to get the robust list from another program (by it's pid)?
>> >
>> > The folks doing checkpoint/restart claim to not need this, so there
>> > might be a way either that or they just haven't hit this problem yet.
>> >
>> > What you are doing sounds like a reasonable use of get_robust_list to me.
>> >
>>
>> 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.

-- 
Thanks,
//richard
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