linux-kernel - Re: [PATCH] cpufreq: Fix NULL reference crash while accessing policy->governor

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Message-ID: <20160127102223.GN10898@e106622-lin>
Date:	Wed, 27 Jan 2016 10:22:23 +0000
From:	Juri Lelli <juri.lelli@....com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	Viresh Kumar <viresh.kumar@...aro.org>,
	linaro-kernel@...ts.linaro.org, linux-pm@...r.kernel.org,
	"# v4 . 2+" <stable@...r.kernel.org>,
	open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] cpufreq: Fix NULL reference crash while accessing
 policy->governor_data

On 26/01/16 23:49, Rafael J. Wysocki wrote:
> On Tuesday, January 26, 2016 06:01:19 PM Juri Lelli wrote:
> > On 26/01/16 09:57, Juri Lelli wrote:
> > > Hi Viresh,
> > > 
> > > On 25/01/16 22:33, Viresh Kumar wrote:
> > > > There is a little race discovered by Juri, where we are able to:
> > > > - create and read a sysfs file before policy->governor_data is being set
> > > >   to a non NULL value.
> > > >   OR
> > > > - set policy->governor_data to NULL, and reading a file before being
> > > >   destroyed.
> > > > 
> 
> [cut]
> 
> > 
> > So, this goes away with your patch (that I forward ported) and a small
> > additional fix on top of that.
> 
> Which patch exactly is that?
> 

As Viresh said, this is:

 cpufreq: Access governor's sysfs attributes without 'policy->rwsem'
 http://www.linux-arm.org/git?p=linux-jl.git;a=commit;h=d3eb02ed23732de2c8671377316a190c38b8fe93

Apologies for the confusion; I was already talking with Viresh on IRC
about it.

Best,

- Juri