linux-kernel - Re: [PATCH 2/3] slab_common: clear pointers to per memcg caches on destroy

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Message-Id: <20151008141735.d545d3fa1ab0244f69c41cdf@linux-foundation.org>
Date:	Thu, 8 Oct 2015 14:17:35 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Vladimir Davydov <vdavydov@...tuozzo.com>
Cc:	Christoph Lameter <cl@...ux.com>,
	Pekka Enberg <penberg@...nel.org>,
	David Rientjes <rientjes@...gle.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>, <linux-mm@...ck.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/3] slab_common: clear pointers to per memcg caches on
 destroy

On Thu, 8 Oct 2015 19:02:40 +0300 Vladimir Davydov <vdavydov@...tuozzo.com> wrote:

> Currently, we do not clear pointers to per memcg caches in the
> memcg_params.memcg_caches array when a global cache is destroyed with
> kmem_cache_destroy. It is fine if the global cache does get destroyed.
> However, a cache can be left on the list if it still has active objects
> when kmem_cache_destroy is called (due to a memory leak). If this
> happens, the entries in the array will point to already freed areas,
> which is likely to result in data corruption when the cache is reused
> (via slab merging).

It's important that we report these leaks so the kernel bug can get
fixed.  The patch doesn't add such detection and reporting, but it
could do so?

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