linux-kernel - [PATCH 4.4 093/143] KVM: nVMX: unconditionally cancel preemption timer in free

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Date:   Mon, 18 Feb 2019 14:43:41 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Peter Shier <pshier@...gle.com>,
        Jim Mattson <jmattson@...gle.com>,
        Felix Wilhelm <fwilhelm@...gle.com>, stable@...nel.org,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: [PATCH 4.4 093/143] KVM: nVMX: unconditionally cancel preemption timer in free_nested (CVE-2019-7221)

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

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

From: Peter Shier <pshier@...gle.com>

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@...gle.com>
Reported-by: Jim Mattson <jmattson@...gle.com>
Reviewed-by: Jim Mattson <jmattson@...gle.com>
Reported-by: Felix Wilhelm <fwilhelm@...gle.com>
Cc: stable@...nel.org
Message-Id: <20181011184646.154065-1-pshier@...gle.com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

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

--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -6965,6 +6965,7 @@ static void free_nested(struct vcpu_vmx
 	if (!vmx->nested.vmxon)
 		return;
 
+	hrtimer_cancel(&vmx->nested.preemption_timer);
 	vmx->nested.vmxon = false;
 	free_vpid(vmx->nested.vpid02);
 	nested_release_vmcs12(vmx);