[PATCH 3.18 071/108] KVM: nVMX: unconditionally cancel preemption timer in free_nested (CVE-2019-7221)

[Greg Kroah-Hartman]

3.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Peter Shier <pshier@xxxxxxxxxx>

commit ecec76885bcfe3294685dc363fd1273df0d5d65f upstream.

Bugzilla: 1671904

There are multiple code paths where an hrtimer may have been started to
emulate an L1 VMX preemption timer that can result in a call to free_nested
without an intervening L2 exit where the hrtimer is normally
cancelled. Unconditionally cancel in free_nested to cover all cases.

Embargoed until Feb 7th 2019.

Signed-off-by: Peter Shier <pshier@xxxxxxxxxx>
Reported-by: Jim Mattson <jmattson@xxxxxxxxxx>
Reviewed-by: Jim Mattson <jmattson@xxxxxxxxxx>
Reported-by: Felix Wilhelm <fwilhelm@xxxxxxxxxx>
Cc: stable@xxxxxxxxxx
Message-Id: <20181011184646.154065-1-pshier@xxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 arch/x86/kvm/vmx.c |    1 +
 1 file changed, 1 insertion(+)

--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -6295,6 +6295,7 @@ static void free_nested(struct vcpu_vmx
 	if (!vmx->nested.vmxon)
 		return;
 
+	hrtimer_cancel(&vmx->nested.preemption_timer);
 	vmx->nested.vmxon = false;
 	nested_release_vmcs12(vmx);
 	if (enable_shadow_vmcs)