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

[Paolo Bonzini]

From: Peter Shier <pshier@xxxxxxxxxx>

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

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 8ff20523661b..d8ea4ebd79e7 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -211,6 +211,7 @@ static void free_nested(struct kvm_vcpu *vcpu)
 	if (!vmx->nested.vmxon && !vmx->nested.smm.vmxon)
 		return;
 
+	hrtimer_cancel(&vmx->nested.preemption_timer);
 	vmx->nested.vmxon = false;
 	vmx->nested.smm.vmxon = false;
 	free_vpid(vmx->nested.vpid02);
-- 
1.8.3.1