[xen/f21] Hypervisor memory corruption due to x86 emulator flaw

[myoung]

commit 5806231158e42eabd0b5ba83d4c0973a0ed82b9d
Author: Michael Young <m.a.young at durham.ac.uk>
Date:   Wed Mar 11 20:26:19 2015 +0000

    Hypervisor memory corruption due to x86 emulator flaw

 xen.spec     |  8 +++++++-
 xsa123.patch | 24 ++++++++++++++++++++++++
 2 files changed, 31 insertions(+), 1 deletion(-)
---
diff --git a/xen.spec b/xen.spec
index a85a0e3..e27a7c6 100644
--- a/xen.spec
+++ b/xen.spec
@@ -53,7 +53,7 @@
 Summary: Xen is a virtual machine monitor
 Name:    xen
 Version: 4.4.1
-Release: 13%{?dist}
+Release: 14%{?dist}
 Group:   Development/Libraries
 License: GPLv2+ and LGPLv2+ and BSD
 URL:     http://xen.org/
@@ -121,6 +121,7 @@ Patch40: xsa116.patch
 Patch41: xsa118-4.4.patch
 Patch42: xsa121.patch
 Patch43: xsa122.patch
+Patch44: xsa123.patch
 
 Patch100: xen-configure-xend.patch
 
@@ -326,6 +327,7 @@ manage Xen virtual machines.
 %patch41 -p1
 %patch42 -p1
 %patch43 -p1
+%patch44 -p1
 
 %patch100 -p1
 
@@ -929,6 +931,10 @@ rm -rf %{buildroot}
 %endif
 
 %changelog
+* Wed Mar 11 2015 Michael Young <m.a.young at durham.ac.uk> - 4.4.1-14
+- Hypervisor memory corruption due to x86 emulator flaw [XSA-123,
+	CVE-2015-2151] (#1200398)
+
 * Thu Mar 05 2015 Michael Young <m.a.young at durham.ac.uk> - 4.4.1-13
 - enable building pngs from fig files which is working again
 - fix oxenstored.service preset preuninstall script
diff --git a/xsa123.patch b/xsa123.patch
new file mode 100644
index 0000000..653996d
--- /dev/null
+++ b/xsa123.patch
@@ -0,0 +1,24 @@
+x86emul: fully ignore segment override for register-only operations
+
+For ModRM encoded instructions with register operands we must not
+overwrite ea.mem.seg (if a - bogus in that case - segment override was
+present) as it aliases with ea.reg.
+
+This is CVE-2015-2151 / XSA-123.
+
+Reported-by: Felix Wilhelm <fwilhelm at ernw.de>
+Signed-off-by: Jan Beulich <jbeulich at suse.com>
+Reviewed-by: Tim Deegan <tim at xen.org>
+Reviewed-by: Keir Fraser <keir at xen.org>
+
+--- a/xen/arch/x86/x86_emulate/x86_emulate.c
++++ b/xen/arch/x86/x86_emulate/x86_emulate.c
+@@ -1757,7 +1757,7 @@ x86_emulate(
+         }
+     }
+ 
+-    if ( override_seg != -1 )
++    if ( override_seg != -1 && ea.type == OP_MEM )
+         ea.mem.seg = override_seg;
+ 
+     /* Early operand adjustments. */