lkml.org 
[lkml]   [2016]   [May]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [PATCH v8 1/4] x86/KASLR: Clarify identity map interface
From
On Tue, May 10, 2016 at 11:24 PM, Ingo Molnar <mingo@kernel.org> wrote:
>
> * Kees Cook <keescook@chromium.org> wrote:
>
>> +/*
>> + * Mapping information structure passed to kernel_ident_mapping_init().
>> + * Due to relocation, pointers must be assigned at run time not build time.
>> + */
>> +static struct x86_mapping_info mapping_info = {
>> + .pmd_flag = __PAGE_KERNEL_LARGE_EXEC,
>> +};
>
>> +void initialize_identity_maps(void)
>> {
>> + /* Init mapping_info with run-time function/buffer pointers. */
>> + mapping_info.alloc_pgt_page = alloc_pgt_page;
>> + mapping_info.context = &pgt_data;
>
> Could you please outline the precise failure mode? What gets executed when, which
> pointer gets relocated and which not, and exactly when does it pose a problem,
> etc.

It's the issue described at the top of misc.c:

/*
* WARNING!!
* This code is compiled with -fPIC and it is relocated dynamically at
* run time, but no relocation processing is performed. This means that
* it is not safe to place pointers in static structures.
*/

Should this be repeated in each .c file maybe as a reminder?

If the rest of the patches look good, we could clean this up as a
following patch? What do you think?

-Kees

--
Kees Cook
Chrome OS & Brillo Security

\
 
 \ /
  Last update: 2016-05-11 17:41    [W:0.053 / U:0.276 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site