Date:   Fri, 3 Feb 2023 14:27:09 +0000
From:   Hyeonggon Yoo <42.hyeyoo@gmail.com>
To:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc:     linux-mm@kvack.org, Christoph Lameter <cl@linux.com>,
        Pekka Enberg <penberg@kernel.org>,
        David Rientjes <rientjes@google.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Vlastimil Babka <vbabka@suse.cz>,
        Roman Gushchin <roman.gushchin@linux.dev>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm/slub: fix memory leak with using debugfs_lookup()
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References: <20230202142022.2300096-1-gregkh@linuxfoundation.org>
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On Thu, Feb 02, 2023 at 03:20:22PM +0100, Greg Kroah-Hartman wrote:
> When calling debugfs_lookup() the result must have dput() called on it,
> otherwise the memory will leak over time.  To make things simpler, just
> call debugfs_lookup_and_remove() instead which handles all of the logic
> at once.
> 
> Cc: Christoph Lameter <cl@linux.com>
> Cc: Pekka Enberg <penberg@kernel.org>
> Cc: David Rientjes <rientjes@google.com>
> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Vlastimil Babka <vbabka@suse.cz>
> Cc: Roman Gushchin <roman.gushchin@linux.dev>
> Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>
> Cc: linux-mm@kvack.org
> Cc: linux-kernel@vger.kernel.org
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> ---
>  mm/slub.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/slub.c b/mm/slub.c
> index 13459c69095a..4880e461fcc5 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -6449,7 +6449,7 @@ static void debugfs_slab_add(struct kmem_cache *s)
>  
>  void debugfs_slab_release(struct kmem_cache *s)
>  {
> -	debugfs_remove_recursive(debugfs_lookup(s->name, slab_debugfs_root));
> +	debugfs_lookup_and_remove(s->name, slab_debugfs_root);
>  }

Looks good to me.
Reviewed-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>

Thank you for fixing this.

>  static int __init slab_debugfs_init(void)
> -- 
> 2.39.1
>