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

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Message-ID: <CA+1xoqdJ=mF6MUPRYm7CmE_fa8GshtjxUpwwYPCKY4ob+gDAeQ@mail.gmail.com>
Date:	Sun, 18 Nov 2012 23:05:04 -0500
From:	Sasha Levin <levinsasha928@...il.com>
To:	Kees Cook <keescook@...omium.org>
Cc:	Sasha Levin <sasha.levin@...cle.com>, 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

Hi Kees,

On Thu, Oct 18, 2012 at 6:39 PM, Kees Cook <keescook@...omium.org> wrote:
> 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?

I still see this one in -rc6, is there anything to get rid of it
before the release?


Thanks,
Sasha
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