linux-kernel - Re: [PATCH] platform/x86: asus-wireless: Fix NULL pointer dereference

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Message-ID: <20180407155006.GA11256@fury>
Date:   Sat, 7 Apr 2018 08:50:06 -0700
From:   Darren Hart <dvhart@...radead.org>
To:     João Paulo Rechi Vita <jprvita@...il.com>
Cc:     Corentin Chary <corentin.chary@...il.com>,
        Andy Shevchenko <andy@...radead.org>,
        platform-driver-x86@...r.kernel.org,
        acpi4asus-user@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
        linux@...lessm.com, Dun Hum <bitter.taste@....com>,
        João Paulo Rechi Vita 
        <jprvita@...lessm.com>
Subject: Re: [PATCH] platform/x86: asus-wireless: Fix NULL pointer dereference

On Fri, Apr 06, 2018 at 10:37:29PM -0700, João Paulo Rechi Vita wrote:
> When the module is removed the led workqueue is destroyed in the remove
> callback, before the led device is unregistered from the led subsystem.
> 
> This leads to a NULL pointer derefence when the led device is
> unregistered automatically later as part of the module removal cleanup.
> Bellow is the backtrace showing the problem.
> 

Thanks João Paulo,
...

> Unregistering the led device on the remove callback before destroying the
> workqueue avoids this problem.
> 
> https://bugzilla.kernel.org/show_bug.cgi?id=196097
> 
> Reported-by: Dun Hum <bitter.taste@....com>
> Signed-off-by: João Paulo Rechi Vita <jprvita@...lessm.com>
> ---
>  drivers/platform/x86/asus-wireless.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/platform/x86/asus-wireless.c b/drivers/platform/x86/asus-wireless.c
> index 343e12547660..ecd715c82de5 100644
> --- a/drivers/platform/x86/asus-wireless.c
> +++ b/drivers/platform/x86/asus-wireless.c
> @@ -181,6 +181,7 @@ static int asus_wireless_remove(struct acpi_device *adev)
>  {
>  	struct asus_wireless_data *data = acpi_driver_data(adev);
>  
> +	devm_led_classdev_unregister(&adev->dev, &data->led);
>  	if (data->wq)
>  		destroy_workqueue(data->wq);
>  	return 0;

asus_wireless_add only calls devm_led_classdev_register() iff the workqueue is
successfully created. It seems like it would make sense to move the
devm_led_classdev_unregister() call within the 'if (data->wq)' condition block.

This should also cc stable.

Thanks,

-- 
Darren Hart
VMware Open Source Technology Center