lkml.org 
[lkml]   [2014]   [Apr]   [30]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[tip:x86/espfix] x86-32, espfix: Remove filter for espfix32 due to race
Commit-ID:  246f2d2ee1d715e1077fc47d61c394569c8ee692
Gitweb: http://git.kernel.org/tip/246f2d2ee1d715e1077fc47d61c394569c8ee692
Author: H. Peter Anvin <hpa@linux.intel.com>
AuthorDate: Wed, 30 Apr 2014 14:03:25 -0700
Committer: H. Peter Anvin <hpa@linux.intel.com>
CommitDate: Wed, 30 Apr 2014 14:14:49 -0700

x86-32, espfix: Remove filter for espfix32 due to race

It is not safe to use LAR to filter when to go down the espfix path,
because the LDT is per-process (rather than per-thread) and another
thread might change the descriptors behind our back. Fortunately it
is always *safe* (if a bit slow) to go down the espfix path, and a
32-bit LDT stack segment is extremely rare.

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Link: http://lkml.kernel.org/r/1398816946-3351-1-git-send-email-hpa@linux.intel.com
Cc: <stable@vger.kernel.org> # consider after upstream merge
---
arch/x86/kernel/entry_32.S | 5 -----
1 file changed, 5 deletions(-)

diff --git a/arch/x86/kernel/entry_32.S b/arch/x86/kernel/entry_32.S
index a2a4f46..2780b8f 100644
--- a/arch/x86/kernel/entry_32.S
+++ b/arch/x86/kernel/entry_32.S
@@ -551,11 +551,6 @@ ENTRY(iret_exc)

CFI_RESTORE_STATE
ldt_ss:
- larl PT_OLDSS(%esp), %eax
- jnz restore_nocheck
- testl $0x00400000, %eax # returning to 32bit stack?
- jnz restore_nocheck # allright, normal return
-
#ifdef CONFIG_PARAVIRT
/*
* The kernel can't run on a non-flat stack if paravirt mode

\
 
 \ /
  Last update: 2014-04-30 23:41    [W:0.309 / U:0.032 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site