linux-kernel - Re: [PATCH] intel_menlow: prevent NULL pointer dereference

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Message-ID: <20160608203846.GG28348@f23x64.localdomain>
Date:	Wed, 8 Jun 2016 13:38:46 -0700
From:	Darren Hart <dvhart@...radead.org>
To:	Vincent Stehlé <vincent.stehle@...el.com>
Cc:	platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org,
	Sujith Thomas <sujith.thomas@...el.com>,
	Zhang Rui <rui.zhang@...el.com>,
	Len Brown <len.brown@...el.com>,
	Rafael Wysocki <rjw@...ysocki.net>
Subject: Re: [PATCH] intel_menlow: prevent NULL pointer dereference

On Wed, May 25, 2016 at 04:20:11PM +0200, Vincent Stehlé wrote:
> The function acpi_driver_data() will dereference its parameter; make sure
> to check for NULL pointer before we call it.

+Rafael

Under what circumstances can the .remove op be called with a NULL struct
acpi_device * as a parameter? From what I can see, most acpi_* calls accpeting
an acpi_device rely on it not being null, and they are regularly called from
driver remove functions.

Did you observe an explicit failure or can you describe a call path where this
can occur?


> 
> Signed-off-by: Vincent Stehlé <vincent.stehle@...el.com>
> Cc: Sujith Thomas <sujith.thomas@...el.com>
> Cc: Darren Hart <dvhart@...radead.org>
> Cc: Zhang Rui <rui.zhang@...el.com>
> Cc: Len Brown <len.brown@...el.com>
> ---
>  drivers/platform/x86/intel_menlow.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/platform/x86/intel_menlow.c b/drivers/platform/x86/intel_menlow.c
> index 0a919d8..185a1bd 100644
> --- a/drivers/platform/x86/intel_menlow.c
> +++ b/drivers/platform/x86/intel_menlow.c
> @@ -196,9 +196,13 @@ static int intel_menlow_memory_add(struct acpi_device *device)
>  
>  static int intel_menlow_memory_remove(struct acpi_device *device)
>  {
> -	struct thermal_cooling_device *cdev = acpi_driver_data(device);
> +	struct thermal_cooling_device *cdev;
> +
> +	if (!device)
> +		return -EINVAL;
>  
> -	if (!device || !cdev)
> +	cdev = acpi_driver_data(device);
> +	if (!cdev)
>  		return -EINVAL;
>  
>  	sysfs_remove_link(&device->dev.kobj, "thermal_cooling");
> -- 
> 2.8.1
> 
> 

-- 
Darren Hart
Intel Open Source Technology Center