Commit 8c6de56a authored Oct 30, 2019 by Boris Ostrovsky Committed by Paolo Bonzini Jan 30, 2020

x86/kvm: Be careful not to clear KVM_VCPU_FLUSH_TLB bit



kvm_steal_time_set_preempted() may accidentally clear KVM_VCPU_FLUSH_TLB
bit if it is called more than once while VCPU is preempted.

This is part of CVE-2019-3016.

(This bug was also independently discovered by Jim Mattson
<jmattson@google.com>)

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: Joao Martins <joao.m.martins@oracle.com>
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

parent ae608821

arch/x86/kvm/x86.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -3504,6 +3504,9 @@ static void kvm_steal_time_set_preempted(struct kvm_vcpu *vcpu)
		if (!(vcpu->arch.st.msr_val & KVM_MSR_ENABLED))
		return;

		if (vcpu->arch.st.steal.preempted)
		return;

		vcpu->arch.st.steal.preempted = KVM_VCPU_PREEMPTED;

		kvm_write_guest_offset_cached(vcpu->kvm, &vcpu->arch.st.stime,

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