On Wed, May 14, 2014 at 04:02:01PM +0800, Dave Young wrote:
> X86 will pass setup_data region while necessary, these regions could be
> overwitten by kernel due to kaslr.
>
> Thus iterate and add setup regions to mem_avoid[] in this patch.
> Set max mem avoid entries 32, hopefully it will be enough.
>
> Signed-off-by: Dave Young <dyo...@redhat.com>
> ---
> arch/x86/boot/compressed/aslr.c | 30 ++++++++++++++++++++++++++++--
> 1 file changed, 28 insertions(+), 2 deletions(-)
>
> Index: linux-2.6/arch/x86/boot/compressed/aslr.c
> ===================================================================
> --- linux-2.6.orig/arch/x86/boot/compressed/aslr.c
> +++ linux-2.6/arch/x86/boot/compressed/aslr.c
> @@ -110,8 +110,9 @@ struct mem_vector {
> unsigned long size;
> };
>
> -#define MEM_AVOID_MAX 5
> +#define MEM_AVOID_MAX 32
> static struct mem_vector mem_avoid[MEM_AVOID_MAX];
> +static int mem_avoid_nr;
>
> static bool mem_contains(struct mem_vector *region, struct mem_vector *item)
> {
> @@ -135,6 +136,28 @@ static bool mem_overlaps(struct mem_vect
> return true;
> }
>
> +static void mem_avoid_setup_data(void)
> +{
> + struct setup_data *data;
> + u64 pa_data;
> +
> + if (mem_avoid_nr >= MEM_AVOID_MAX) {
> + debug_putstr("KASLR: too many setup_data ranges.\n");
> + return;
> + }
> +
> + pa_data = real_mode->hdr.setup_data;
> + while (pa_data) {
> + data = (struct setup_data *)pa_data;
> + if (pa_data < CONFIG_RANDOMIZE_BASE_MAX_OFFSET) {
> + mem_avoid[mem_avoid_nr].start = pa_data;
> + mem_avoid[mem_avoid_nr].size = sizeof(*data) +
> data->len;
> + mem_avoid_nr++;
> + }
> + pa_data = data->next;
> + }
> +}
> +
I have no idea if this real_mode->hdr.setup_data examination is correct,
so not commenting on that.
What prevents the loop from overflowing the table?
Additinally reaching the limit should at least result in a big fat warning.
--
Mateusz Guzik
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