x86/kvm: Be careful not to clear KVM_VCPU_FLUSH_TLB bit
commit 8c6de56a42
upstream.
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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@ -3499,6 +3499,9 @@ static void kvm_steal_time_set_preempted(struct kvm_vcpu *vcpu)
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if (!(vcpu->arch.st.msr_val & KVM_MSR_ENABLED))
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if (!(vcpu->arch.st.msr_val & KVM_MSR_ENABLED))
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return;
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return;
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if (vcpu->arch.st.steal.preempted)
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return;
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vcpu->arch.st.steal.preempted = KVM_VCPU_PREEMPTED;
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vcpu->arch.st.steal.preempted = KVM_VCPU_PREEMPTED;
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kvm_write_guest_offset_cached(vcpu->kvm, &vcpu->arch.st.stime,
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kvm_write_guest_offset_cached(vcpu->kvm, &vcpu->arch.st.stime,
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