linux-kernel - Re: [RESEND PATCH] cpufreq: unnecesary double free in pcc_cpufreq_do

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Message-ID: <1285877732.2180.7.camel@cowboy>
Date:	Thu, 30 Sep 2010 16:15:32 -0400
From:	Davidlohr Bueso <dave@....org>
To:	David Rientjes <rientjes@...gle.com>,
	Pekka Enberg <penberg@...nel.org>
Cc:	davej@...hat.com, cpufreq@...r.kernel.org,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RESEND PATCH] cpufreq: unnecesary double free in
 pcc_cpufreq_do_osc

On Thu, 2010-09-30 at 13:02 -0700, David Rientjes wrote:
> On Thu, 30 Sep 2010, Davidlohr Bueso wrote:
> 
> > x86, cpufreq: avoid an unnecessary double free when finished in pcc_cpufreq_do_osc()
> > 
> > There is no need to fall through the out_free label thus saving a kfree call.
> > 
> > Signed-off-by: Davidlohr Bueso <dave@....org>
> > ---
> >  arch/x86/kernel/cpu/cpufreq/pcc-cpufreq.c |    2 ++
> >  1 files changed, 2 insertions(+), 0 deletions(-)
> > 
> > diff --git a/arch/x86/kernel/cpu/cpufreq/pcc-cpufreq.c b/arch/x86/kernel/cpu/cpufreq/pcc-cpufreq.c
> > index 994230d..db7dc35 100644
> > --- a/arch/x86/kernel/cpu/cpufreq/pcc-cpufreq.c
> > +++ b/arch/x86/kernel/cpu/cpufreq/pcc-cpufreq.c
> > @@ -379,6 +379,8 @@ static int __init pcc_cpufreq_do_osc(acpi_handle *handle)
> >  	if (!(supported & 0x1))
> >  		return -ENODEV;
> >  
> > +	return ret;
> > +
> >  out_free:
> >  	kfree(output.pointer);
> >  	return ret;
> 
> Why is the kfree() unnecessary?  acpi_evaluate_object() will allocate a 
> new output.pointer if it returns 0, so at this point in the code you would 
> now be leaking the buffer.
> 
> Instead, it would probably be better to fix the existing memory leaks in 
> that function where we return -ENODEV without going to out_free when 
> output.length is non-zero.
> 

Silly me, I must be asleep still. Pekka's attached patch is just right.
Sorry for the noise.

Davidlohr


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