From 82b79aceed17a3ca45e2b87b4c95965ba19f803e Mon Sep 17 00:00:00 2001
From: Jan Beulich <jbeulich@suse.com>
Date: Wed, 27 Nov 2013 09:45:16 +0100
Subject: [PATCH] x86/HVM: only allow ring 0 guest code to make hypercalls

Anything else would allow for privilege escalation.

This is CVE-2013-4554 / XSA-76.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
master commit: 5c447caaf49192c7b2c057ffbb565ce72aac666d
master date: 2013-11-27 09:01:49 +0100
---
 xen/arch/x86/hvm/hvm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index f066353ced..6dd40678c0 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -3343,7 +3343,7 @@ int hvm_do_hypercall(struct cpu_user_regs *regs)
     case 4:
     case 2:
         hvm_get_segment_register(curr, x86_seg_ss, &sreg);
-        if ( unlikely(sreg.attr.fields.dpl == 3) )
+        if ( unlikely(sreg.attr.fields.dpl) )
         {
     default:
             regs->eax = -EPERM;