Re: [PATCH] x86, kaslr: avoid setup_data when picking location

Kees Cook
2014-10-01T18:08:58Z

On Wed, Oct 1, 2014 at 11:01 AM, H. Peter Anvin <hpa@zytor.com> wrote:
> On 09/11/2014 09:19 AM, Kees Cook wrote:
>> --- a/arch/x86/boot/compressed/aslr.c
>> +++ b/arch/x86/boot/compressed/aslr.c
>> @@ -183,12 +183,27 @@ static void mem_avoid_init(unsigned long input, unsigned long input_size,
>> static bool mem_avoid_overlap(struct mem_vector *img)
>> {
>> int i;
>> + struct setup_data *ptr;
>>
>> for (i = 0; i < MEM_AVOID_MAX; i++) {
>> if (mem_overlaps(img, &mem_avoid[i]))
>> return true;
>> }
>>
>> + /* Avoid all entries in the setup_data linked list. */
>> + ptr = (struct setup_data *)(unsigned long)real_mode->hdr.setup_data;
>> + while (ptr) {
>> + struct mem_vector avoid;
>> +
>> + avoid.start = (u64)ptr;
>> + avoid.size = sizeof(*ptr) + ptr->len;
>> +
>> + if (mem_overlaps(img, &avoid))
>> + return true;
>> +
>> + ptr = (struct setup_data *)(unsigned long)ptr->next;
>> + }
>> +
>> return false;
>> }
>>
>>
>
> The use of (u64) in the assignment to avoid.start gives a nuisance
> warning on 32 bits.

Ah, good catch! This should be (unsigned long), I think. Shall I send
a follow-up patch, or do you want to fix this directly?

-Kees

--
Kees Cook
Chrome OS Security