From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001 From: Boris Ostrovsky Date: Fri, 31 Jan 2020 08:06:40 -0300 Subject: [PATCH] x86/kvm: Be careful not to clear KVM_VCPU_FLUSH_TLB bit CVE-2019-3016 CVE-2020-3016 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 ) Signed-off-by: Boris Ostrovsky Reviewed-by: Joao Martins Signed-off-by: Thadeu Lima de Souza Cascardo Signed-off-by: Thomas Lamprecht --- arch/x86/kvm/x86.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 778b3a899769..92d8e4ebba16 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -3393,6 +3393,9 @@ 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,