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Subject: Re: yama: lockdep warning on yama_ptracer_del
From: Kees Cook <keescook@chromium.org>
To: Sasha Levin <sasha.levin@oracle.com>
Cc: james.l.morris@oracle.com, John Johansen <john.johansen@canonical.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        linux-security-module@vger.kernel.org,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Dave Jones <davej@redhat.com>
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On Wed, Oct 17, 2012 at 8:10 PM, Sasha Levin <sasha.levin@oracle.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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