From mboxrd@z Thu Jan  1 00:00:00 1970
From: Pekka Enberg <penberg@cs.helsinki.fi>
Subject: Re: [Bugme-new] [Bug 33502] New: Caught 64-bit read from uninitialized
 memory in __alloc_skb
Date: Tue, 10 May 2011 13:03:41 +0300
Message-ID: <4DC90D7D.9030808@cs.helsinki.fi>
References: <bug-33502-10286@https.bugzilla.kernel.org/>	 <20110418153852.153d3ed3.akpm@linux-foundation.org>	 <1303181466.4152.39.camel@edumazet-laptop>	 <1303182557.4152.48.camel@edumazet-laptop>	 <1303183217.4152.49.camel@edumazet-laptop>	 <alpine.DEB.2.00.1104191210011.17888@router.home>	 <1303244270.2756.3.camel@edumazet-laptop> <4DAE7579.3020400@cs.helsinki.fi>	 <1303279470.2756.17.camel@edumazet-laptop>	 <1303285519.4dae8f0fdf9b1@imp.free.fr>  <4DAE901C.2090809@cs.helsinki.fi>	 <1303286998.3186.18.camel@edumazet-laptop>	 <1303290464.3186.32.camel@edumazet-laptop>	 <1303293765.3186.74.camel@edumazet-laptop>	 <alpine.DEB.2.00.1104200904440.8634@router.home>	 <1303309591.3186.84.camel@edumazet-laptop>	 <alpine.DEB.2.00.1104200942020.9266@router.home>	 <1303311687.3186.100.camel@edumaze
 t-laptop>	 <alpine.DEB.2.00.1105092241390.6784@tiger>	 <alpine.DEB.2.00.1105091502260.26839@router.home> <1305016988.2614.6.camel@edumazet-laptop>
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Cc: Christoph Lameter <cl@linux.com>,
	Pekka Enberg <penberg@cs.helsinki.fi>,
	casteyde.christian@free.fr,
	Andrew Morton <akpm@linux-foundation.org>,
	netdev@vger.kernel.org, bugzilla-daemon@bugzilla.kernel.org,
	bugme-daemon@bugzilla.kernel.org,
	Vegard Nossum <vegardno@ifi.uio.no>
To: Eric Dumazet <eric.dumazet@gmail.com>
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On 5/10/11 11:43 AM, Eric Dumazet wrote:
> Le lundi 09 mai 2011 =C3=A0 15:04 -0500, Christoph Lameter a =C3=A9cr=
it :
>> On Mon, 9 May 2011, Pekka Enberg wrote:
>>
>>> On Wed, 20 Apr 2011, Eric Dumazet wrote:
>>>> [PATCH v4] slub: dont use cmpxchg_double if KMEMCHECK or DEBUG_PAG=
EALLOC
>>>>
>>>> Christian Casteyde reported a KMEMCHECK splat in slub code.
>>>>
>>>> Problem is now we are lockless and allow IRQ in slab_alloc(), the =
object
>>>> we manipulate from freelist can be allocated and freed right befor=
e we
>>>> try to read object->next.
>>>>
>>>> Same problem can happen with DEBUG_PAGEALLOC
>>>>
>>>> Just dont use cmpxchg_double() if either CONFIG_KMEMCHECK or
>>>> CONFIG_DEBUG_PAGEALLOC is defined.
>>> Christoph, Eric, is this still relevant after commit 1759415 ("slub=
: Remove
>>> CONFIG_CMPXCHG_LOCAL ifdeffery") in slab/next of slab.git?
>> There is still an issue and now you can no longer fix the thing thro=
ugh
>> CONFIG_CMPXCHG_LOCAL.
>>
>> It needs to be legal for slub to deref the counter even if the objec=
t has
>> been freed.
>>
> I am trying to follow things but honestly I am lost.
>
> Isnt commit 1759415e63 planned for 2.6.40 ?
> ( ref :
> http://git.kernel.org/?p=3Dlinux/kernel/git/penberg/slab-2.6.git;a=3D=
commitdiff;h=3D1759415e630e5db0dd2390df9f94892cbfb9a8a2 )
>
> How shall we fix things for 2.6.39 ? I thought my patch was OK for th=
at.
>
>
> Its a bit hard to work with you on this stuff, for a report I made ag=
es
> ago, I find it incredible its not yet fixed in linux-2.6.
>
Can't we fix the issue by putting kmemcheck_mark_initialized() to=20
set_freepointer()?