lkml.org 
[lkml]   [2018]   [Feb]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [tip:x86/pti] x86/speculation: Use Indirect Branch Prediction Barrier in context switch
From
Date
On Wed, 2018-01-31 at 08:03 +0100, Dominik Brodowski wrote:
> Whether a process needs protection by IBPB on context switches is a
> different question to whether a process should be allowed to be dumped,
> though the former may be a superset of the latter. Enable IBPB on all
> context switches to a different userspace process, until we have a clear
> mitigation strategy for userspace against Spectre-v2 designed and
> implemented.
>
> ...
>                 if (tsk && tsk->mm &&
> -                   tsk->mm->context.ctx_id != last_ctx_id &&
> -                   get_dumpable(tsk->mm) != SUID_DUMP_USER)
> +                   tsk->mm->context.ctx_id != last_ctx_id)
>                         indirect_branch_prediction_barrier();


I understand your argument and I sympathise.

But that's going to hurt a *lot*, and we don't even have a viable
proof-of-concept for a user←→user Spectre v2 attack, do we? It's only
theoretical?

Show a working PoC and it makes the argument somewhat more
convincing...[unhandled content-type:application/x-pkcs7-signature]
\
 
 \ /
  Last update: 2018-02-01 09:33    [W:0.125 / U:0.168 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site