Date: Fri, 3 Aug 2012 13:38:46 +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 1:35 PM, Cyrill Gorcunov <gorcunov@...nvz.org> wrote: > 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 <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(). > > 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). Please see my first mail above. c/r is not the only user. :-P -- Thanks, //richard
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