linux-kernel - Re: yama: lockdep warning on yama_ptracer

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Message-ID: <CAGXu5jKSD8nRMJ11DpKRe8M79W9MZ2eowAafXOQ9_WCj4dZXug@mail.gmail.com>
Date:	Thu, 18 Oct 2012 15:39:45 -0700
From:	Kees Cook <keescook@...omium.org>
To:	Sasha Levin <sasha.levin@...cle.com>
Cc:	james.l.morris@...cle.com,
	John Johansen <john.johansen@...onical.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-security-module@...r.kernel.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Dave Jones <davej@...hat.com>
Subject: Re: yama: lockdep warning on yama_ptracer_del

On Wed, Oct 17, 2012 at 8:10 PM, Sasha Levin <sasha.levin@...cle.com> wrote:
> Hi all,
>
> I was fuzzing with trinity within a KVM tools guest (lkvm) on a linux-next kernel, and got the
> following dump which I believe to be noise due to how the timers work - but I'm not 100% sure.
> ...
> [  954.674123]  Possible interrupt unsafe locking scenario:
> [  954.674123]
> [  954.674123]        CPU0                    CPU1
> [  954.674123]        ----                    ----
> [  954.674123]   lock(ptracer_relations_lock);
> [  954.674123]                                local_irq_disable();
> [  954.674123]                                lock(&(&new_timer->it_lock)->rlock);
> [  954.674123]                                lock(ptracer_relations_lock);
> [  954.674123]   <Interrupt>
> [  954.674123]     lock(&(&new_timer->it_lock)->rlock);
> [  954.674123]
> [  954.674123]  *** DEADLOCK ***

I've been wanting to get rid of the Yama ptracer_relations_lock
anyway, so maybe I should do that now just to avoid this case at all?

-Kees

-- 
Kees Cook
Chrome OS Security
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