linux-kernel - Re: [PATCH] kobject: Safe return of kobject_get

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Date:   Wed, 23 Jun 2021 17:11:26 +0200
From:   "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
To:     Christian Löhle <CLoehle@...erstone.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "rafael@...nel.org" <rafael@...nel.org>
Subject: Re: [PATCH] kobject: Safe return of kobject_get_path with NULL

On Wed, Jun 23, 2021 at 02:47:35PM +0000, Christian Löhle wrote:
> Prevent NULL dereference within get_kobj_path_length
> 
> Calling kobject_get_path could provoke a NULL dereference
> if NULL was passed. while fill_kobj_path will return
> with a sane 0 for NULL, kobjet_get_path_length did not.

Who passes NULL into that function?  Shouldn't that be fixed first?

> 
> Signed-off-by: Christian Loehle <cloehle@...erstone.com>
> ---
>  lib/kobject.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/lib/kobject.c b/lib/kobject.c
> index ea53b30cf483..735159c13a94 100644
> --- a/lib/kobject.c
> +++ b/lib/kobject.c
> @@ -130,6 +130,8 @@ static int get_kobj_path_length(struct kobject *kobj)
>  {
>  	int length = 1;
>  	struct kobject *parent = kobj;
> +	if (!kobj)
> +		return 0;
>  
>  	/* walk up the ancestors until we hit the one pointing to the
>  	 * root.
> -- 
> 2.32.0
> 
> Hyperstone GmbH | Line-Eid-Strasse 3 | 78467 Konstanz
> Managing Directors: Dr. Jan Peter Berns.
> Commercial register of local courts: Freiburg HRB381782
> 

Pleaase always run your patches through checkpatch.pl so you do not get
maintainers asking you to use checkpatch.pl...

thanks,

greg k-h