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

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Message-ID: <20120803110247.GB11952@moon>
Date:	Fri, 3 Aug 2012 15:02:47 +0400
From:	Cyrill Gorcunov <gorcunov@...nvz.org>
To:	richard -rw- weinberger <richard.weinberger@...il.com>,
	Pavel Emelyanov <xemul@...allels.com>
Cc:	"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 03, 2012 at 12:17:43PM +0200, richard -rw- weinberger wrote:
> On Thu, Aug 2, 2012 at 1:11 PM, Eric W. Biederman <ebiederm@...ssion.com> wrote:
> > richard -rw- weinberger <richard.weinberger@...il.com> writes:
> >
> >> On Fri, Mar 23, 2012 at 8:08 PM, Kees Cook <keescook@...omium.org> wrote:
> >>> Notify get_robust_list users that the syscall is going away.
> >>>
> >>> Suggested-by: Thomas Gleixner <tglx@...utronix.de>
> >>> Signed-off-by: Kees Cook <keescook@...omium.org>
> >>> ---
> >>
> >> 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?

	Cyrill
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