linux-kernel - Re: [linux-next-20130422] Bug in SLAB?

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Date:	Sun, 07 Jul 2013 18:58:53 +0300
From:	Pekka Enberg <penberg@...nel.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>, cl@...ux.com,
	glommer@...allels.com, linux-kernel@...r.kernel.org
Subject: Re: [linux-next-20130422] Bug in SLAB?

On 7/2/13 10:12 PM, Andrew Morton wrote:
> On Tue, 2 Jul 2013 21:49:26 +0900 Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp> wrote:
>
>> Some architectures (e.g. powerpc built with CONFIG_PPC_256K_PAGES=y
>> CONFIG_FORCE_MAX_ZONEORDER=11) get PAGE_SHIFT + MAX_ORDER > 26.
>>
>> In 3.10 kernels, CONFIG_LOCKDEP=y with PAGE_SHIFT + MAX_ORDER > 26 makes
>> init_lock_keys() dereference beyond kmalloc_caches[26].
>> This leads to an unbootable system (kernel panic at initializing SLAB)
>> if one of kmalloc_caches[26...PAGE_SHIFT+MAX_ORDER-1] is not NULL.
>>
>> Fix this by making sure that init_lock_keys() does not dereference beyond
>> kmalloc_caches[26] arrays.
>
> Nice, thanks.  Pekka, please grab.
>
>
> From: Christoph Lameter <cl@...ux.com>
> Subject: slab: fix init_lock_keys
>
> Some architectures (e.g. powerpc built with CONFIG_PPC_256K_PAGES=y
> CONFIG_FORCE_MAX_ZONEORDER=11) get PAGE_SHIFT + MAX_ORDER > 26.
>
> In 3.10 kernels, CONFIG_LOCKDEP=y with PAGE_SHIFT + MAX_ORDER > 26 makes
> init_lock_keys() dereference beyond kmalloc_caches[26].
> This leads to an unbootable system (kernel panic at initializing SLAB)
> if one of kmalloc_caches[26...PAGE_SHIFT+MAX_ORDER-1] is not NULL.
>
> Fix this by making sure that init_lock_keys() does not dereference beyond
> kmalloc_caches[26] arrays.
>
> Signed-off-by: Christoph Lameter <cl@...ux.com>
> Reported-by: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
> Cc: Pekka Enberg <penberg@...nel.org>
> Cc: <stable@...r.kernel.org>	[3.10.x]
> Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
> ---
>
>   mm/slab.c |    2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff -puN mm/slab.c~slab-fix-init_lock_keys mm/slab.c
> --- a/mm/slab.c~slab-fix-init_lock_keys
> +++ a/mm/slab.c
> @@ -565,7 +565,7 @@ static void init_node_lock_keys(int q)
>   	if (slab_state < UP)
>   		return;
>
> -	for (i = 1; i < PAGE_SHIFT + MAX_ORDER; i++) {
> +	for (i = 1; i <= KMALLOC_SHIFT_HIGH; i++) {
>   		struct kmem_cache_node *n;
>   		struct kmem_cache *cache = kmalloc_caches[i];
>
> _
>

Grabbed, thanks a lot Andrew!
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