linux-kernel - Re: [RFC][PATCH 1/5] mm/slab_common: allow NULL cache pointer in kmem_cache

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Date:	Wed, 17 Jun 2015 16:14:59 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Minchan Kim <minchan@...nel.org>,
	Christoph Lameter <cl@...ux.com>,
	Pekka Enberg <penberg@...nel.org>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Michal Hocko <mhocko@...e.cz>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, sergey.senozhatsky.work@...il.com
Subject: Re: [RFC][PATCH 1/5] mm/slab_common: allow NULL cache pointer in
 kmem_cache_destroy()

On Tue, 9 Jun 2015, Sergey Senozhatsky wrote:

> kmem_cache_destroy() does not tolerate a NULL kmem_cache pointer
> argument and performs a NULL-pointer dereference. This requires
> additional attention and effort from developers/reviewers and
> forces all kmem_cache_destroy() callers (200+ as of 4.1) to do
> a NULL check
> 
> 	if (cache)
> 		kmem_cache_destroy(cache);
> 
> Or, otherwise, be invalid kmem_cache_destroy() users.
> 
> Tweak kmem_cache_destroy() and NULL-check the pointer there.
> 
> Proposed by Andrew Morton.
> 
> Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@...il.com>
> Reported-by: Andrew Morton <akpm@...ux-foundation.org>
> LKML-reference: https://lkml.org/lkml/2015/6/8/583

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

kmem_cache_destroy() isn't a fastpath, this is long overdue.  Now where's 
the patch to remove the NULL checks from the callers? ;)
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