[PATCH] mm/slub: fix memory leak with using debugfs_lookup()

[PATCH] mm/slub: fix memory leak with using debugfs_lookup()

[Greg Kroah-Hartman]

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);
 }
 
 static int __init slab_debugfs_init(void)
-- 
2.39.1

Re: [PATCH] mm/slub: fix memory leak with using debugfs_lookup()

[Hyeonggon Yoo]

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
> 

Re: [PATCH] mm/slub: fix memory leak with using debugfs_lookup()

[Roman Gushchin]

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>

Good catch!

Acked-by: Roman Gushchin <roman.gushchin@linux.dev>

Thanks!

Re: [PATCH] mm/slub: fix memory leak with using debugfs_lookup()

[David Rientjes]

On Thu, 2 Feb 2023, 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>

Acked-by: David Rientjes <rientjes@google.com>

Re: [PATCH] mm/slub: fix memory leak with using debugfs_lookup()

[Vlastimil Babka]

On 2/2/23 15:20, 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>

Thanks, added to slab/for-6.3/fixes

> ---
>  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);
>  }
>  
>  static int __init slab_debugfs_init(void)