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x86/kvm: Be careful not to clear KVM_VCPU_FLUSH_TLB bit

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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>
This commit is contained in:
Boris Ostrovsky 2019-10-30 19:01:31 +00:00 committed by Paolo Bonzini
parent ae6088216c
commit 8c6de56a42
1 changed files with 3 additions and 0 deletions
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arch/x86/kvm/x86.c
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@ -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,