linux-kernel - Re: [PATCH v2] mfd: fix unintentional NULL check in menelaus_set

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Date:	Mon, 2 Jun 2014 08:44:22 -0700
From:	Tony Lindgren <tony@...mide.com>
To:	Jingoo Han <jg1.han@...sung.com>
Cc:	'Emil Goode' <emilgoode@...il.com>,
	'Lee Jones' <lee.jones@...aro.org>,
	linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org,
	'Samuel Ortiz' <sameo@...ux.intel.com>,
	'Trilok Soni' <tsoni@...eaurora.org>,
	Aaro Koskinen <aaro.koskinen@....fi>,
	Jarkko Nikula <jarkko.nikula@...mer.com>
Subject: Re: [PATCH v2] mfd: fix unintentional NULL check in
 menelaus_set_voltage()

* Jingoo Han <jg1.han@...sung.com> [140528 18:45]:
> On Thursday, May 29, 2014 1:44 AM, Emil Goode wrote:
> > 
> > The struct menelaus_vtg pointer vtg cannot be NULL here
> > so the condition is never true and if it ever was true
> > it would lead to a NULL pointer dereference when we goto
> > label set_voltage.
> > 
> > Before the below patch was applied the code was:
> > 
> > if (vtg == 0)
> > 
> > The intention was to check if vtg_val is 0.
> > 
> > commit 59a9f7a32adf6537b4e4db8ca204eeb77d7a634e
> > ("mfd: menelaus: Use NULL instead of 0")
> > 
> > Signed-off-by: Emil Goode <emilgoode@...il.com>
> > ---
> > v2: Changed (vtg_val == 0) to (!vtg_val)
> > 
> >  drivers/mfd/menelaus.c |    2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/mfd/menelaus.c b/drivers/mfd/menelaus.c
> > index ad25bfa..40df76a 100644
> > --- a/drivers/mfd/menelaus.c
> > +++ b/drivers/mfd/menelaus.c
> > @@ -466,7 +466,7 @@ static int menelaus_set_voltage(const struct menelaus_vtg *vtg, int mV,
> >  	struct i2c_client *c = the_menelaus->client;
> > 
> >  	mutex_lock(&the_menelaus->lock);
> > -	if (!vtg)
> > +	if (!vtg_val)
> >  		goto set_voltage;
> 
> (+cc Trilok Soni, Tony Lindgren)
> 
> In this case, if 'vtg_val' is 0, setting voltage as 0 for
> registers such as MENELAUS_xxx_CTRLx will be skipped. So,
> it is not possible to set the voltage value as 0.
> 
> Is it right? If not, how about just removing this check and
> the label 'set_voltage'?

Added Aaro and Jarkko to Cc.

Regards,

Tony
 
> Best regards,
> Jingoo Han
> 
> > 
> >  	ret = menelaus_read_reg(vtg->vtg_reg);
> > --
> > 1.7.10.4
> 
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