lkml.org 
[lkml]   [2015]   [Jul]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v3 1/3] x86/ldt: Make modify_ldt synchronous
On Wed, Jul 22, 2015 at 12:23:46PM -0700, Andy Lutomirski wrote:
> modify_ldt has questionable locking and does not synchronize
> threads. Improve it: redesign the locking and synchronize all
> threads' LDTs using an IPI on all modifications.
>
> This will dramatically slow down modify_ldt in multithreaded
> programs, but there shouldn't be any multithreaded programs that
> care about modify_ldt's performance in the first place.
>
> Cc: stable@vger.kernel.org
> Signed-off-by: Andy Lutomirski <luto@kernel.org>

...

> +struct ldt_struct {
> + /*
> + * Xen requires page-aligned LDTs with special permissions. This is
> + * needed to prevent us from installing evil descriptors such as
> + * call gates. On native, we could merge the ldt_struct and LDT
> + * allocations, but it's not worth trying to optimize.

I don't think baremetal should care about xen and frankly, this is
getting ridiculous, slowly - baremetal has to wait with a potentially
critical security fix just because it breaks xen. Dammit, this level of
intrusiveness into x86 should've never been allowed.

--
Regards/Gruss,
Boris.

ECO tip #101: Trim your mails when you reply.
--


\
 
 \ /
  Last update: 2015-07-24 09:01    [W:0.130 / U:0.316 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site