This is a note to let you know that I've just added the patch titled
x86-32, espfix: Remove filter for espfix32 due to race
to the 3.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-32-espfix-remove-filter-for-espfix32-due-to-race.patch
and it can be found in the queue-3.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 246f2d2ee1d715e1077fc47d61c394569c8ee692 Mon Sep 17 00:00:00 2001
From: "H. Peter Anvin" <hpa@xxxxxxxxxxxxxxx>
Date: Wed, 30 Apr 2014 14:03:25 -0700
Subject: x86-32, espfix: Remove filter for espfix32 due to race
From: "H. Peter Anvin" <hpa@xxxxxxxxxxxxxxx>
commit 246f2d2ee1d715e1077fc47d61c394569c8ee692 upstream.
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@xxxxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/1398816946-3351-1-git-send-email-hpa@xxxxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/kernel/entry_32.S | 5 -----
1 file changed, 5 deletions(-)
--- a/arch/x86/kernel/entry_32.S
+++ b/arch/x86/kernel/entry_32.S
@@ -550,11 +550,6 @@ 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
Patches currently in stable-queue which might be from hpa@xxxxxxxxxxxxxxx are
queue-3.4/x86-32-espfix-remove-filter-for-espfix32-due-to-race.patch
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