linux-kernel - Re: [PATCH] drm:vkms: Add NULL value after free function In function vkms_exit, after kfree(default_config), give specific NULL value to pointer default

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Message-ID: <YKJ5KU4ZOXvUPM8o@phenom.ffwll.local>
Date:   Mon, 17 May 2021 16:09:45 +0200
From:   Daniel Vetter <daniel@...ll.ch>
To:     Hao Peng <penghaob@...ontech.com>
Cc:     rodrigosiqueiramelo@...il.com, melissa.srw@...il.com,
        hamohammed.sa@...il.com, daniel@...ll.ch, airlied@...ux.ie,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm:vkms: Add NULL value after free function In function
 vkms_exit, after kfree(default_config), give specific NULL value to pointer
 default_config to avoid wild pointer.

On Wed, May 12, 2021 at 07:55:54PM +0800, Hao Peng wrote:
> Signed-off-by: Hao Peng <penghaob@...ontech.com>
> ---
>  drivers/gpu/drm/vkms/vkms_drv.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/gpu/drm/vkms/vkms_drv.c b/drivers/gpu/drm/vkms/vkms_drv.c
> index 2173b82606f6..6c63201db5d0 100644
> --- a/drivers/gpu/drm/vkms/vkms_drv.c
> +++ b/drivers/gpu/drm/vkms/vkms_drv.c
> @@ -227,6 +227,7 @@ static void __exit vkms_exit(void)
>  		vkms_destroy(default_config);
>  
>  	kfree(default_config);
> +	default_config = NULL;

This is the last thing before the module us unloaded, which means no one
can access default_config anymore. So also no point in clearing it.
-Daniel

>  }
>  
>  module_init(vkms_init);
> -- 
> 2.20.1
> 
> 
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch