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

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Date:	Mon, 6 May 2013 08:59:39 +0200
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Christoph Lameter <cl@...ux.com>
Cc:	Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
	glommer@...allels.com, Pekka Enberg <penberg@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [linux-next-20130422] Bug in SLAB?

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.

> +                       return NULL;
> +               }
> +
>                 i = kmalloc_index(size);
>
>  #ifdef CONFIG_ZONE_DMA
> @@ -172,6 +177,11 @@ static __always_inline void *kmalloc_nod
>                 if (!size)
>                         return ZERO_SIZE_PTR;
>
> +               if (size > KMALLOC_MAX_SIZE) {
> +                       WARN_ON(1);

Idem ditto.

> +                       return NULL;
> +               }
> +
>                 i = kmalloc_index(size);

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
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