linux-kernel - Re: [PATCH] mm: SLAB freelist randomization

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Date:	Fri, 15 Apr 2016 15:26:00 -0700
From:	Joe Perches <joe@...ches.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Garnier <thgarnie@...gle.com>
Cc:	Christoph Lameter <cl@...ux.com>,
	Pekka Enberg <penberg@...nel.org>,
	David Rientjes <rientjes@...gle.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Kees Cook <keescook@...omium.org>, gthelen@...gle.com,
	labbott@...oraproject.org, kernel-hardening@...ts.openwall.com,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH] mm: SLAB freelist randomization

On Fri, 2016-04-15 at 15:00 -0700, Andrew Morton wrote:
> On Fri, 15 Apr 2016 10:25:59 -0700 Thomas Garnier <thgarnie@...gle.com> wrote:
> > Provide an optional config (CONFIG_FREELIST_RANDOM) to randomize the
> > SLAB freelist. The list is randomized during initialization of a new set
> > of pages. The order on different freelist sizes is pre-computed at boot
> > for performance. This security feature reduces the predictability of the
> > kernel SLAB allocator against heap overflows rendering attacks much less
> > stable.

trivia:

> > @@ -1229,6 +1229,61 @@ static void __init set_up_node(struct kmem_cache *cachep, int index)
[]
> > + */
> > +static freelist_idx_t master_list_2[2];
> > +static freelist_idx_t master_list_4[4];
> > +static freelist_idx_t master_list_8[8];
> > +static freelist_idx_t master_list_16[16];
> > +static freelist_idx_t master_list_32[32];
> > +static freelist_idx_t master_list_64[64];
> > +static freelist_idx_t master_list_128[128];
> > +static freelist_idx_t master_list_256[256];
> > +static struct m_list {
> > +	size_t count;
> > +	freelist_idx_t *list;
> > +} master_lists[] = {
> > +	{ ARRAY_SIZE(master_list_2), master_list_2 },
> > +	{ ARRAY_SIZE(master_list_4), master_list_4 },
> > +	{ ARRAY_SIZE(master_list_8), master_list_8 },
> > +	{ ARRAY_SIZE(master_list_16), master_list_16 },
> > +	{ ARRAY_SIZE(master_list_32), master_list_32 },
> > +	{ ARRAY_SIZE(master_list_64), master_list_64 },
> > +	{ ARRAY_SIZE(master_list_128), master_list_128 },
> > +	{ ARRAY_SIZE(master_list_256), master_list_256 },
> > +};

static const struct m_list?