linux-kernel - Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86, core)

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Date:	Fri, 24 Jun 2016 16:05:58 +0200
From:	Michal Hocko <mhocko@...nel.org>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andy Lutomirski <luto@...capital.net>,
	Andy Lutomirski <luto@...nel.org>,
	the arch/x86 maintainers <x86@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
	Borislav Petkov <bp@...en8.de>,
	Nadav Amit <nadav.amit@...il.com>,
	Kees Cook <keescook@...omium.org>,
	Brian Gerst <brgerst@...il.com>,
	"kernel-hardening@...ts.openwall.com" 
	<kernel-hardening@...ts.openwall.com>,
	Josh Poimboeuf <jpoimboe@...hat.com>,
	Jann Horn <jann@...jh.net>,
	Heiko Carstens <heiko.carstens@...ibm.com>
Subject: Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86,
 core)

On Thu 23-06-16 20:52:21, Oleg Nesterov wrote:
> On 06/23, Linus Torvalds wrote:
> >
> > On Thu, Jun 23, 2016 at 10:03 AM, Oleg Nesterov <oleg@...hat.com> wrote:
> > >
> > > Let me quote my previous email ;)
> > >
> > >         And we can't free/nullify it when the parent/debuger reaps a zombie,
> > >         say, mark_oom_victim() expects that get_task_struct() protects
> > >         thread_info as well.
> > >
> > > probably we can fix all such users though...
> >
> > TIF_MEMDIE is indeed a potential problem, but I don't think
> > mark_oom_victim() is actually problematic.
> >
> > mark_oom_victim() is called with either "current",
> 
> This is no longer true in -mm tree.
> 
> But I agree, this is fixable (and in fact I still hope TIF_MEMDIE will die,
> at least in its current form).

We can move the flag to the task_struct. There are still some bits left
there. This would be trivial so that the oom usage doesn't stay in the
way.
-- 
Michal Hocko
SUSE Labs