Re: [PATCH] kobject: Safe return of kobject_get_path with NULL

[gregkh@xxxxxxxxxxxxxxxxxxx]

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@xxxxxxxxxxxxxx>
> ---
>  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
> 
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> 

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

thanks,

greg k-h