linux-kernel - Re: [PATCH 4/5] mm, slub: fix potential use-after-free in slab_debugfs

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Date:   Tue, 5 Oct 2021 12:36:16 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Miaohe Lin <linmiaohe@...wei.com>, akpm@...ux-foundation.org,
        cl@...ux.com, penberg@...nel.org, rientjes@...gle.com,
        iamjoonsoo.kim@....com
Cc:     gregkh@...uxfoundation.org, faiyazm@...eaurora.org,
        andreyknvl@...il.com, ryabinin.a.a@...il.com, thgarnie@...gle.com,
        keescook@...omium.org, bharata@...ux.ibm.com, guro@...com,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/5] mm, slub: fix potential use-after-free in
 slab_debugfs_fops

On 9/16/21 14:39, Miaohe Lin wrote:
> When sysfs_slab_add failed, we shouldn't call debugfs_slab_add() for s
> because s will be freed soon. And slab_debugfs_fops will use s later
> leading to a use-after-free.
> 
> Fixes: 64dd68497be7 ("mm: slub: move sysfs slab alloc/free interfaces to debugfs")
> Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>

Reviewed-by: Vlastimil Babka <vbabka@...e.cz>

> ---
>  mm/slub.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/slub.c b/mm/slub.c
> index bf1793fb4ce5..f3df0f04a472 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -4887,13 +4887,15 @@ int __kmem_cache_create(struct kmem_cache *s, slab_flags_t flags)
>  		return 0;
>  
>  	err = sysfs_slab_add(s);
> -	if (err)
> +	if (err) {
>  		__kmem_cache_release(s);
> +		return err;
> +	}
>  
>  	if (s->flags & SLAB_STORE_USER)
>  		debugfs_slab_add(s);
>  
> -	return err;
> +	return 0;
>  }
>  
>  void *__kmalloc_track_caller(size_t size, gfp_t gfpflags, unsigned long caller)
>