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

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Date:	Mon, 6 May 2013 10:27:47 +0300
From:	Pekka Enberg <penberg@...nel.org>
To:	Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:	Christoph Lameter <cl@...ux.com>,
	Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
	Glauber Costa <glommer@...allels.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [linux-next-20130422] Bug in SLAB?

On Mon, May 6, 2013 at 9:59 AM, Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
> On Fri, May 3, 2013 at 5:43 PM, Christoph Lameter <cl@...ux.com> wrote:
>> Subject: slab: Return NULL for oversized allocations
>>
>> The inline path seems to have changed the SLAB behavior for very large
>> kmalloc allocations. This patch restores the old behavior but also
>> adds diagnostics so that we can figure where in the code these
>> large allocations occur.
>>
>> Signed-off-by: Christoph Lameter <cl@...ux.com>
>>
>>
>> Index: linux/include/linux/slab_def.h
>> ===================================================================
>> --- linux.orig/include/linux/slab_def.h 2013-05-03 10:36:46.019564801 -0500
>> +++ linux/include/linux/slab_def.h      2013-05-03 10:37:28.860302188 -0500
>> @@ -126,6 +126,11 @@ static __always_inline void *kmalloc(siz
>>                 if (!size)
>>                         return ZERO_SIZE_PTR;
>>
>> +               if (size > KMALLOC_MAX_SIZE) {
>> +                       WARN_ON(1);
>
> As we were worried about this being triggered frm userspace, this needs
> some rate limiting, to avoid flooding the kernel logs.

I changed it to WARN_ON_ONCE():

https://git.kernel.org/cgit/linux/kernel/git/penberg/linux.git/commit/?h=slab/next
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