KVM: VMX: Check cpl before emulating debug register access

Debug registers may only be accessed from cpl 0.  Unfortunately, vmx will
code to emulate the instruction even though it was issued from guest
userspace, possibly leading to an unexpected trap later.

Cc: stable@kernel.org
Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index cc6e00a9f724..f3812014bd0b 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -2934,6 +2934,8 @@ static int handle_dr(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
         unsigned long val;
         int dr, reg;
 
+        if (!kvm_require_cpl(vcpu, 0))
+                return 1;
         dr = vmcs_readl(GUEST_DR7);
         if (dr & DR7_GD) {
                 /*