Re: [PATCH] mm: SLAB freelist randomization

[Thomas Garnier]

Thanks for the comments. I will address them in a v2 early next week.

If anyone has other comments, please let me know.

Thomas

On Fri, Apr 15, 2016 at 3:26 PM, Joe Perches <joe@xxxxxxxxxxx> wrote:
> On Fri, 2016-04-15 at 15:00 -0700, Andrew Morton wrote:
>> On Fri, 15 Apr 2016 10:25:59 -0700 Thomas Garnier <thgarnie@xxxxxxxxxx> 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?
>