linux-kernel - Re: od_set_powersave_bias: NULL pointer dereference

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Message-ID: <CAKohpom_jHQeR2FKFS3-RkxpPrJvekw8pDb-qnApnzu-VqreBQ@mail.gmail.com>
Date:	Wed, 26 Jun 2013 20:02:29 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Jacob Shin <jacob.shin@....com>
Cc:	Tim Gardner <tim.gardner@...onical.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	LKML <linux-kernel@...r.kernel.org>, cpufreq@...r.kernel.org,
	linux-pm@...r.kernel.org
Subject: Re: od_set_powersave_bias: NULL pointer dereference

On 26 June 2013 19:58, Jacob Shin <jacob.shin@....com> wrote:
> On Wed, Jun 26, 2013 at 12:18:27PM +0530, Viresh Kumar wrote:

>> I am not sure if this is enough. What if we had ondemand as the
>> governor initially, then we changed it to something else. Now also
>> cur_policy contains a address and isn't zero.
>
> Right, so we check below ..
>
>>
>> >                 cpumask_or(&done, &done, policy->cpus);
>> > +
>> > +               if (policy->governor != &cpufreq_gov_ondemand)
>> > +                       continue;
>
> This should catch that case no ?

Policy might be freed and reallocated by then. And so doing
policy->governor is dangerous.
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