linux-kernel - Re: [PATCH] slub: Fix kmem_cache_destroy() with SLAB_DESTROY_BY

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Message-ID: <4AA01F54.4040808@gmail.com>
Date:	Thu, 03 Sep 2009 21:56:04 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Pekka Enberg <penberg@...helsinki.fi>
CC:	Christoph Lameter <cl@...ux-foundation.org>,
	Zdenek Kabelac <zdenek.kabelac@...il.com>,
	Patrick McHardy <kaber@...sh.net>, Robin Holt <holt@....com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Jesper Dangaard Brouer <hawk@...x.dk>,
	Linux Netdev List <netdev@...r.kernel.org>,
	Netfilter Developers <netfilter-devel@...r.kernel.org>,
	paulmck@...ux.vnet.ibm.com, "stable@...nel.org" <stable@...nel.org>
Subject: Re: [PATCH] slub: Fix kmem_cache_destroy() with SLAB_DESTROY_BY_RCU

Pekka Enberg a écrit :
> On Thu, Sep 3, 2009 at 5:18 PM, Eric Dumazet<eric.dumazet@...il.com> wrote:
>> Here is the second patch (RCU thing). Stable candidate
>>
>> [PATCH] slub: Fix kmem_cache_destroy() with SLAB_DESTROY_BY_RCU
>>
>> kmem_cache_destroy() should call rcu_barrier() *after* kmem_cache_close()
>> and *before* sysfs_slab_remove() or risk rcu_free_slab()
>> being called after kmem_cache is deleted (kfreed).
>>
>> rmmod nf_conntrack can crash the machine because it has to
>> kmem_cache_destroy() a SLAB_DESTROY_BY_RCU enabled cache.
> 
> Do we have a bugzilla URL for this?

Well, I can crash my 2.6.30.5 machine just doing rmmod nf_conntrack

(You'll need CONFIG_SLUB_DEBUG_ON or equivalent)

Original Zdenek report : http://thread.gmane.org/gmane.linux.kernel/876016/focus=876086

> 
>> Reported-by: Zdenek Kabelac <zdenek.kabelac@...il.com>
>> Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>
>> Acked-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> 
> OK, this is in for-next now and queued for 2.6.31. If you guys want to
> fix this in a different way, lets do that in 2.6.32.

Seems the right thing IMHO
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