lkml.org 
[lkml]   [2013]   [Apr]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [kernel-hardening] Re: [PATCH] x86: make IDT read-only
From
On Tue, Apr 9, 2013 at 11:46 AM, Kees Cook <keescook@chromium.org> wrote:
> On Tue, Apr 9, 2013 at 11:39 AM, H. Peter Anvin <hpa@zytor.com> wrote:
>> On 04/09/2013 11:31 AM, Kees Cook wrote:
>>>>> ...
>>>>> 0xffff880001e00000-0xffff88001fe00000 480M RW PSE GLB NX pmd
>>>>>
>>>>
>>>> That is the 1:1 memory map area...
>>>
>>> Meaning what?
>>>
>>> -Kees
>>>
>>
>> That's the area in which we just map 1:1 to memory. Anything allocated
>> with e.g. kmalloc() ends up with those addresses.
>
> Ah-ha! Yes, I see now when comparing the debug/kernel_page_tables
> reports. It's just the High Kernel Mapping that we care about.
> Addresses outside that range are less of a leak. Excellent, then GDT
> may not be a problem. Whew.

The GDT is a problem if the address returned by 'sgdt' is
kernel-writable - it doesn't necessarily reveal the random offset, but
I'm pretty sure that writing to the GDT could cause privilege
escalation.

>
> Does the v2 IDT patch look okay, BTW?
>
> -Kees
>
> --
> Kees Cook
> Chrome OS Security


\
 
 \ /
  Last update: 2013-04-09 21:21    [W:0.118 / U:2.416 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site