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Subject: Re: [PATCH] drivers/macintosh: Correct potential double free
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Julia Lawall <julia@diku.dk>
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Date: Mon, 29 Mar 2010 21:57:15 +1100
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On Mon, 2010-03-29 at 11:39 +0200, Julia Lawall wrote:
> From: Julia Lawall <julia@diku.dk>
> 
> The conditionals were testing different values, but then all freeing the
> same one, which could result in a double free.
> 
> A simplified version of the semantic match that finds this problem is as
> follows: (http://coccinelle.lip6.fr/)

Thanks. I'll stick that in my -next branch as soon as I open it :-)

Cheers,
Ben.

> // <smpl>
> @@
> expression x,e;
> identifier f;
> iterator I;
> statement S;
> @@
> 
> *kfree(x);
> ... when != &x
>     when != x = e
>     when != I(x,...) S
> *x
> // </smpl>
> 
> Signed-off-by: Julia Lawall <julia@diku.dk>
> 
> ---
>  drivers/macintosh/windfarm_pm91.c   |    9 +++------
>  1 files changed, 3 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/macintosh/windfarm_pm91.c b/drivers/macintosh/windfarm_pm91.c
> index bea9916..3442732 100644
> --- a/drivers/macintosh/windfarm_pm91.c
> +++ b/drivers/macintosh/windfarm_pm91.c
> @@ -687,12 +687,9 @@ static int __devexit wf_smu_remove(struct platform_device *ddev)
>  		wf_put_control(cpufreq_clamp);
>  
>  	/* Destroy control loops state structures */
> -	if (wf_smu_slots_fans)
> -		kfree(wf_smu_cpu_fans);
> -	if (wf_smu_drive_fans)
> -		kfree(wf_smu_cpu_fans);
> -	if (wf_smu_cpu_fans)
> -		kfree(wf_smu_cpu_fans);
> +	kfree(wf_smu_slots_fans);
> +	kfree(wf_smu_drive_fans);
> +	kfree(wf_smu_cpu_fans);
>  
>  	return 0;
>  }