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From: Paolo Bonzini <pbonzini@redhat.com>
To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>, stable@vger.kernel.org
Subject: [FYI PATCH 1/5] x86/kvm: Be careful not to clear KVM_VCPU_FLUSH_TLB bit
Date: Thu, 30 Jan 2020 19:01:52 +0100
Message-ID: <1580407316-11391-2-git-send-email-pbonzini@redhat.com> (raw)
In-Reply-To: <1580407316-11391-1-git-send-email-pbonzini@redhat.com>

From: Boris Ostrovsky <boris.ostrovsky@oracle.com>

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>
---
 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 cf91713..8c93691 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -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,
-- 
1.8.3.1


  reply index

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-30 18:01 [FYI PATCH 0/5] Missing TLB flushes Paolo Bonzini
2020-01-30 18:01 ` Paolo Bonzini [this message]
2020-01-30 18:01 ` [FYI PATCH 2/5] x86/kvm: Introduce kvm_(un)map_gfn() Paolo Bonzini
2020-01-30 18:01 ` [FYI PATCH 3/5] x86/kvm: Cache gfn to pfn translation Paolo Bonzini
2020-01-30 18:01 ` [FYI PATCH 4/5] x86/KVM: Make sure KVM_VCPU_FLUSH_TLB flag is not missed Paolo Bonzini
2020-01-30 18:01 ` [FYI PATCH 5/5] x86/KVM: Clean up host's steal time structure Paolo Bonzini
2020-02-01  5:53 ` [FYI PATCH 0/5] Missing TLB flushes Wanpeng Li

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