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Fix for CVE-2013-0190 xen corruption with 32bit pvops (rhbz 896051 896038)

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Justin M. Forbes 2013-01-16 09:57:24 -06:00
commit e4e27aa511
2 changed files with 71 additions and 0 deletions
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9
kernel.spec
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@ -786,6 +786,9 @@ Patch2150: 3.7.3-stable-queue.patch
#rhbz 886946
Patch21234: iwlegacy-fix-IBSS-cleanup.patch
#rhbz 896051 896038 CVE-2013-0190
Patch21250: xen-fix-stack-corruption-in-xen_failsafe_callback.patch
# END OF PATCH DEFINITIONS
%endif
@ -1511,6 +1514,9 @@ ApplyPatch 3.7.3-stable-queue.patch
#rhbz 886948
ApplyPatch iwlegacy-fix-IBSS-cleanup.patch
#rhbz 896051 896038 CVE-2013-0190
ApplyPatch xen-fix-stack-corruption-in-xen_failsafe_callback.patch
# END OF PATCH APPLICATIONS
%endif
@ -2383,6 +2389,9 @@ fi
# ||----w |
# || ||
%changelog
* Wed Jan 16 2013 Justin M. Forbes <jforbes@redhat.com> 3.7.2-204
- Fix for CVE-2013-0190 xen corruption with 32bit pvops (rhbz 896051 896038)
* Wed Jan 16 2013 Josh Boyer <jwboyer@redhat.com>
- Add patch from Stanislaw Gruszka to fix iwlegacy IBSS cleanup (rhbz 886946)

62
xen-fix-stack-corruption-in-xen_failsafe_callback.patch Normal file
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@ -0,0 +1,62 @@
From 38174c8c07ad638cd18285ba402b59076849dc21 Mon Sep 17 00:00:00 2001
From: Andrew Cooper <andrew.cooper3@citrix.com>
Date: Thu, 10 Jan 2013 17:16:30 +0000
Subject: [PATCH] xen: Fix stack corruption in xen_failsafe_callback for 32bit PVOPS guests.
There has been an error on the xen_failsafe_callback path for failed
iret, which causes the stack pointer to be wrong when entering the
iret_exc error path. This can result in the kernel crashing.
In the classic kernel case, the relevant code looked a little like:
popl %eax # Error code from hypervisor
jz 5f
addl $16,%esp
jmp iret_exc # Hypervisor said iret fault
5: addl $16,%esp
# Hypervisor said segment selector fault
Here, there are two identical addls on either option of a branch which
appears to have been optimised by hoisting it above the jz, and
converting it to an lea, which leaves the flags register unaffected.
In the PVOPS case, the code looks like:
popl_cfi %eax # Error from the hypervisor
lea 16(%esp),%esp # Add $16 before choosing fault path
CFI_ADJUST_CFA_OFFSET -16
jz 5f
addl $16,%esp # Incorrectly adjust %esp again
jmp iret_exc
It is possible unprivileged userspace applications to cause this
behaviour, for example by loading an LDT code selector, then changing
the code selector to be not-present. At this point, there is a race
condition where it is possible for the hypervisor to return back to
userspace from an interrupt, fault on its own iret, and inject a
failsafe_callback into the kernel.
This bug has been present since the introduction of Xen PVOPS support
in commit 5ead97c84 (xen: Core Xen implementation), in 2.6.23.
Signed-off-by: Frediano Ziglio <frediano.ziglio@citrix.com>
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
arch/x86/kernel/entry_32.S | 1 -
1 files changed, 0 insertions(+), 1 deletions(-)
diff --git a/arch/x86/kernel/entry_32.S b/arch/x86/kernel/entry_32.S
index ff84d54..6ed91d9 100644
--- a/arch/x86/kernel/entry_32.S
+++ b/arch/x86/kernel/entry_32.S
@@ -1065,7 +1065,6 @@ ENTRY(xen_failsafe_callback)
lea 16(%esp),%esp
CFI_ADJUST_CFA_OFFSET -16
jz 5f
- addl $16,%esp
jmp iret_exc
5: pushl_cfi $-1 /* orig_ax = -1 => not a system call */
SAVE_ALL
--
1.7.2.5