linux-kernel - Re: [PATCH] intel_idle: Check cpu_idle_get_driver() for NULL before dereferencing it.

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Date:	Mon, 6 Aug 2012 10:50:10 -0400
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	lenb@...nel.org, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] intel_idle: Check cpu_idle_get_driver() for NULL before
 dereferencing it.

On Sat, Aug 04, 2012 at 11:56:35PM +0200, Rafael J. Wysocki wrote:
> On Thursday, August 02, 2012, Konrad Rzeszutek Wilk wrote:
> > If the machine is booted without any cpu_idle driver set
> > (b/c disable_cpuidle() has been called) we should follow
> > other users of cpu_idle API and check the return value
> > for NULL before using it.
> > 
> > Reported-by: Mark van Dijk <mark@...ernecto.net>
> > Tested-by: Mark van Dijk <mark@...ernecto.net>
> > Suggested-by: Jan Beulich <JBeulich@...e.com>
> > Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
> > ---
> >  drivers/idle/intel_idle.c |    2 +-
> >  1 files changed, 1 insertions(+), 1 deletions(-)
> > 
> > diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
> > index f559088..7383aa0 100644
> > --- a/drivers/idle/intel_idle.c
> > +++ b/drivers/idle/intel_idle.c
> > @@ -607,7 +607,7 @@ static int __init intel_idle_init(void)
> >  	retval = cpuidle_register_driver(&intel_idle_driver);
> >  	if (retval) {
> 
> What about:
> 
>   		struct cpuidle_driver *drv = cpuidle_get_driver();
> 
>   		printk(KERN_DEBUG PREFIX "intel_idle yielding to %s",
> 			drv ? drv->name : "none");
> 
> >  		printk(KERN_DEBUG PREFIX "intel_idle yielding to %s",
> > -			cpuidle_get_driver()->name);
> > +			cpuidle_get_driver() ? cpuidle_get_driver()->name : "none");
> >  		return retval;
> >  	}
> >  
> > 
> 
> Rafael

Here it is:

>From a8b7aa06cacb5f42a90a0d4a0a1a95e230d43fc6 Mon Sep 17 00:00:00 2001
From: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Date: Thu, 2 Aug 2012 10:31:52 -0400
Subject: [PATCH] intel_idle: Check cpu_idle_get_driver() for NULL before
 dereferencing it.

If the machine is booted without any cpu_idle driver set
(b/c disable_cpuidle() has been called) we should follow
other users of cpu_idle API and check the return value
for NULL before using it.

Reported-by: Mark van Dijk <mark@...ernecto.net>
Tested-by: Mark van Dijk <mark@...ernecto.net>
Suggested-by: Jan Beulich <JBeulich@...e.com>
[v1: Redo per Rafael's suggestion]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
---
 drivers/idle/intel_idle.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
index d0f59c3..6b313af 100644
--- a/drivers/idle/intel_idle.c
+++ b/drivers/idle/intel_idle.c
@@ -556,8 +556,9 @@ static int __init intel_idle_init(void)
 	intel_idle_cpuidle_driver_init();
 	retval = cpuidle_register_driver(&intel_idle_driver);
 	if (retval) {
+		struct cpuidle_driver *drv = cpuidle_get_driver();
 		printk(KERN_DEBUG PREFIX "intel_idle yielding to %s",
-			cpuidle_get_driver()->name);
+			drv ? drv->name : "none");
 		return retval;
 	}
 
-- 
1.7.7.6

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