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

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Message-ID: <Pine.LNX.4.64.0907290657380.17320@ask.diku.dk>
Date:	Wed, 29 Jul 2009 06:58:00 +0200 (CEST)
From:	Julia Lawall <julia@...u.dk>
To:	Jonathan Woithe <jwoithe@...sics.adelaide.edu.au>
Cc:	Paulo Marques <pmarques@...popie.com>, 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

On Wed, 29 Jul 2009, Jonathan Woithe wrote:

> 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.

Looks fine now, thanks.
julia


> 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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