linux-kernel - Re: Re: [PATCH] PM / devfreq: Fix out of bounds access of transition table array

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Date:	Wed, 26 Feb 2014 05:12:03 +0000 (GMT)
From:	함명주 <myungjoo.ham@...sung.com>
To:	Saravana Kannan <skannan@...eaurora.org>
Cc:	박경민 <kyungmin.park@...sung.com>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: Re: [PATCH] PM / devfreq: Fix out of bounds access of transition
 table array

> On 02/23/2014 11:15 PM, Saravana Kannan wrote:
> > The previous_freq value for a device could be an invalid frequency that
> > results in a error value being returned from devfreq_get_freq_level().
> > Check for an error value before using that to index into the transition
> > table.
> >
> > Not doing this check will result in memory corruption when previous_freq is
> > not a valid frequency.
> >
> > Signed-off-by: Saravana Kannan <skannan@...eaurora.org>
> 
> MyungJoo/Kyungmin,
> 
> Would either of you have some time to respond to this?
> 
> Thanks,
> Saravana

Dear Saravana,

> > +	prev_lev = devfreq_get_freq_level(devfreq, devfreq->previous_freq);
> > +	if (prev_lev < 0)
> > +		return 0;

If devfreq_get_freq_level returned error, please return that error
to the caller. You are retuning 0 in that case.

Plus, do you think we are going to change profile->freq_table in run-time?
(by accidently? or intentionally?)

Cheers,
MyungJoo.

> 
> 
> -- 
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> hosted by The Linux Foundation
> 
> 
> 
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