lkml.org 
[lkml]   [2022]   [May]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH V2] x86/sev: Mark the code returning to user space as syscall gap
Hi,

On Tue, Apr 12, 2022 at 08:49:08PM +0800, Lai Jiangshan wrote:
> From: Lai Jiangshan <jiangshan.ljs@antgroup.com>
>
> When returning to user space, the %rsp is user controlled value.
>
> If it is SNP-guest and the hypervisor decides to mess with the code-page
> for this path while a CPU is executing it. This will cause a #VC on
> that CPU and that could hit in the syscall return path and mislead
> the #VC handler.
>
> So make ip_within_syscall_gap() return true in this case.

With the SNP guest patches in tip-tree I think it actually becomes
possible that a #VC exception hits in these parts of the execution
stream. It requires good timing by the attacker, but it is not
impossible. Therefore:

Acked-by: Joerg Roedel <jroedel@suse.de>

--
Jörg Rödel
jroedel@suse.de

SUSE Software Solutions Germany GmbH
Maxfeldstr. 5
90409 Nürnberg
Germany

(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev

\
 
 \ /
  Last update: 2022-05-13 15:40    [W:0.061 / U:0.296 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site