linux-kernel - Re: [PATCH 6/12] drivers/platform/x86: Correct redundant test

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Date:	Wed, 29 Jul 2009 12:12:37 +0930 (CST)
From:	Jonathan Woithe <jwoithe@...sics.adelaide.edu.au>
To:	julia@...u.dk (Julia Lawall)
Cc:	jwoithe@...sics.adelaide.edu.au (Jonathan Woithe),
	pmarques@...popie.com (Paulo Marques),
	linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org
Subject: Re: [PATCH 6/12] drivers/platform/x86: Correct redundant test

Hi Julia

> > > Julia Lawall wrote:
> > > > [...]
> > > > ---
> > > >  drivers/platform/x86/fujitsu-laptop.c          |    3 ---
> > > >  1 files changed, 0 insertions(+), 3 deletions(-)
> > > > 
> > > > diff --git a/drivers/platform/x86/fujitsu-laptop.c b/drivers/platform/x86/fujitsu-laptop.c
> > > > index 218b9a1..5306901 100644
> > > > --- a/drivers/platform/x86/fujitsu-laptop.c
> > > > +++ b/drivers/platform/x86/fujitsu-laptop.c
> > > > @@ -745,9 +745,6 @@ static int acpi_fujitsu_remove(struct acpi_device *device, int type)
> > > >  
> > > >  	fujitsu = acpi_driver_data(device);
> > > >  
> > > > -	if (!device || !acpi_driver_data(device))
> > > > -		return -EINVAL;
> > > > -
> > > 
> > > Shouldn't this still do a:
> > > 
> > >    if (!fujitsu)
> > >      return -EINVAL;
> > > 
> > > to avoid dereferencing a NULL pointer below?
> > 
> > Hmm, yes it should.  Well spotted.  And I'm not certain how the duplicate
> > test on "device" got in there in the first place.  I suspect it came about
> > due to some structural changes made a few versions ago and I failed to
> > notice that the second check became redundant.
> 
> If you are going to check fujitsu afterwards, then I think there is no 
> need to test the result of acpi_driver_data before.

Yes, of course.  I'll wake up soon, promise!

So we're left with this.

Signed-off-by: jwoithe@...sics.adelaide.edu.au <Jonathan Woithe>

--- a/drivers/platform/x86/fujitsu-laptop.c	2009-06-12 19:51:45.333234000 +0930
+++ b/drivers/platform/x86/fujitsu-laptop.c	2009-07-29 12:10:11.504901871 +0930
@@ -740,12 +740,12 @@ static int acpi_fujitsu_remove(struct ac
 {
        struct fujitsu_t *fujitsu = NULL;
 
-	if (!device || !acpi_driver_data(device))
+	if (!device)
 		return -EINVAL;
 
 	fujitsu = acpi_driver_data(device);
 
-	if (!device || !acpi_driver_data(device))
+	if (!fujitsu)
 		return -EINVAL;
 
	fujitsu->acpi_handle = NULL;


Regards
  jonathan
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