linux-kernel - Re: [PATCH 9/11] drivers/platform/x86: Eliminate a NULL pointer dereference

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Message-Id: <201005270921.43049.dmitry.torokhov@gmail.com>
Date:	Thu, 27 May 2010 09:21:42 -0700
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	Julia Lawall <julia@...u.dk>
Cc:	Mattia Dongili <malattia@...ux.it>,
	Matthew Garrett <mjg@...hat.com>,
	platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org
Subject: Re: [PATCH 9/11] drivers/platform/x86: Eliminate a NULL pointer dereference

On Thursday 27 May 2010 05:37:00 am Julia Lawall wrote:
> From: Julia Lawall <julia@...u.dk>
> 
> Give different error messages if device_enum is NULL or if its type field
> has the wrong value.
> 
> A simplified version of the semantic match that finds this problem is as
> follows: (http://coccinelle.lip6.fr/)
> 
> // <smpl>
> @r exists@
> expression E,E1;
> identifier f;
> statement S1,S2,S3;
> @@
> 
> if ((E == NULL && ...) || ...)
> {
>   ... when != if (...) S1 else S2
>       when != E = E1
> * E->f
>   ... when any
>   return ...;
> }
> else S3
> // </smpl>
> 
> Signed-off-by: Julia Lawall <julia@...u.dk>
> 
> ---
> This may be too much clutter for little benefit.  Other, perhaps less
> informative solutions are possible.

Verbosity should be OK but I think that mixing pr_xxx() and naked printks
in the same patch is not very nice.

> 
>  drivers/platform/x86/sony-laptop.c |    8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/platform/x86/sony-laptop.c
> b/drivers/platform/x86/sony-laptop.c index 1387c5f..9db8d2b 100644
> --- a/drivers/platform/x86/sony-laptop.c
> +++ b/drivers/platform/x86/sony-laptop.c
> @@ -1196,8 +1196,12 @@ static void sony_nc_rfkill_setup(struct acpi_device
> *device) }
> 
>  	device_enum = (union acpi_object *) buffer.pointer;
> -	if (!device_enum || device_enum->type != ACPI_TYPE_BUFFER) {
> -		printk(KERN_ERR "Invalid SN06 return object 0x%.2x\n",
> +	if (!device_enum) {
> +		pr_err("Invalid SN06 return object\n");
> +		goto out_no_enum;
> +	}
> +	if (device_enum->type != ACPI_TYPE_BUFFER) {
> +		printk(KERN_ERR "Invalid SN06 return object type 0x%.2x\n",
>  				device_enum->type);
>  		goto out_no_enum;
>  	}

Thanks.

-- 
Dmitry
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