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Date: Fri, 3 Aug 2012 15:35:38 +0400
From: Cyrill Gorcunov <>
To: richard -rw- weinberger <>
Cc: Pavel Emelyanov <>,
	"Eric W. Biederman" <>,
	Kees Cook <>,
	Thomas Gleixner <>,,
	Randy Dunlap <>,
	Darren Hart <>,
	Peter Zijlstra <>,
	Andrew Morton <>,
	Jiri Kosina <>, David Howells <>,
	"Serge E. Hallyn" <>,,,
Subject: Re: [PATCH v2] futex: mark get_robust_list as deprecated

On Fri, Aug 03, 2012 at 01:30:31PM +0200, richard -rw- weinberger wrote:
> On Fri, Aug 3, 2012 at 1:27 PM, Cyrill Gorcunov <> 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().

Yes, and I'm definitely not against that ;) The problem is that this
syscall was marked as deprecated and if people want to drop it we
need to find a way to provide this address back in a sake of c/r.

If c/r is the only _one_ who needs this facility than providing the
address via /proc might be worth thing to do (since I can wrap
it with CONFIG_CHECKPOINT_RESTORE and a regular kernel won't see
this snippet at all).


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