linux-kernel - Re: od_set_powersave_bias: NULL pointer dereference

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Message-ID: <20130626143555.GA2989@jshin-Toonie>
Date:	Wed, 26 Jun 2013 09:35:55 -0500
From:	Jacob Shin <jacob.shin@....com>
To:	Viresh Kumar <viresh.kumar@...aro.org>
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 Wed, Jun 26, 2013 at 08:02:29PM +0530, Viresh Kumar wrote:
> 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.

Hm . any hints on how to check for if ondemand is running on this CPU
or not ? I'm not sure what the best way to handle this is ..

Thanks,

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