+++ /dev/null
-From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
-From: Boris Ostrovsky <boris.ostrovsky@oracle.com>
-Date: Fri, 31 Jan 2020 08:06:43 -0300
-Subject: [PATCH] x86/KVM: Make sure KVM_VCPU_FLUSH_TLB flag is not missed
-
-CVE-2019-3016
-CVE-2020-3016
-
-There is a potential race in record_steal_time() between setting
-host-local vcpu->arch.st.steal.preempted to zero (i.e. clearing
-KVM_VCPU_PREEMPTED) and propagating this value to the guest with
-kvm_write_guest_cached(). Between those two events the guest may
-still see KVM_VCPU_PREEMPTED in its copy of kvm_steal_time, set
-KVM_VCPU_FLUSH_TLB and assume that hypervisor will do the right
-thing. Which it won't.
-
-Instad of copying, we should map kvm_steal_time and that will
-guarantee atomicity of accesses to @preempted.
-
-This is part of CVE-2019-3016.
-
-Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
-Reviewed-by: Joao Martins <joao.m.martins@oracle.com>
-Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
-Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
----
- arch/x86/kvm/x86.c | 49 +++++++++++++++++++++++++++-------------------
- 1 file changed, 29 insertions(+), 20 deletions(-)
-
-diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
-index cb18560b07bc..f63fa5846f08 100644
---- a/arch/x86/kvm/x86.c
-+++ b/arch/x86/kvm/x86.c
-@@ -2488,43 +2488,45 @@ static void kvm_vcpu_flush_tlb(struct kvm_vcpu *vcpu, bool invalidate_gpa)
-
- static void record_steal_time(struct kvm_vcpu *vcpu)
- {
-+ struct kvm_host_map map;
-+ struct kvm_steal_time *st;
-+
- if (!(vcpu->arch.st.msr_val & KVM_MSR_ENABLED))
- return;
-
-- if (unlikely(kvm_read_guest_cached(vcpu->kvm, &vcpu->arch.st.stime,
-- &vcpu->arch.st.steal, sizeof(struct kvm_steal_time))))
-+ /* -EAGAIN is returned in atomic context so we can just return. */
-+ if (kvm_map_gfn(vcpu, vcpu->arch.st.msr_val >> PAGE_SHIFT,
-+ &map, &vcpu->arch.st.cache, false))
- return;
-
-+ st = map.hva +
-+ offset_in_page(vcpu->arch.st.msr_val & KVM_STEAL_VALID_BITS);
-+
- /*
- * Doing a TLB flush here, on the guest's behalf, can avoid
- * expensive IPIs.
- */
-- if (xchg(&vcpu->arch.st.steal.preempted, 0) & KVM_VCPU_FLUSH_TLB)
-+ if (xchg(&st->preempted, 0) & KVM_VCPU_FLUSH_TLB)
- kvm_vcpu_flush_tlb(vcpu, false);
-
-- if (vcpu->arch.st.steal.version & 1)
-- vcpu->arch.st.steal.version += 1; /* first time write, random junk */
-+ vcpu->arch.st.steal.preempted = 0;
-
-- vcpu->arch.st.steal.version += 1;
-+ if (st->version & 1)
-+ st->version += 1; /* first time write, random junk */
-
-- kvm_write_guest_cached(vcpu->kvm, &vcpu->arch.st.stime,
-- &vcpu->arch.st.steal, sizeof(struct kvm_steal_time));
-+ st->version += 1;
-
- smp_wmb();
-
-- vcpu->arch.st.steal.steal += current->sched_info.run_delay -
-+ st->steal += current->sched_info.run_delay -
- vcpu->arch.st.last_steal;
- vcpu->arch.st.last_steal = current->sched_info.run_delay;
-
-- kvm_write_guest_cached(vcpu->kvm, &vcpu->arch.st.stime,
-- &vcpu->arch.st.steal, sizeof(struct kvm_steal_time));
--
- smp_wmb();
-
-- vcpu->arch.st.steal.version += 1;
-+ st->version += 1;
-
-- kvm_write_guest_cached(vcpu->kvm, &vcpu->arch.st.stime,
-- &vcpu->arch.st.steal, sizeof(struct kvm_steal_time));
-+ kvm_unmap_gfn(vcpu, &map, &vcpu->arch.st.cache, true, false);
- }
-
- int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
-@@ -3396,18 +3398,25 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
-
- static void kvm_steal_time_set_preempted(struct kvm_vcpu *vcpu)
- {
-+ struct kvm_host_map map;
-+ struct kvm_steal_time *st;
-+
- 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;
-+ if (kvm_map_gfn(vcpu, vcpu->arch.st.msr_val >> PAGE_SHIFT, &map,
-+ &vcpu->arch.st.cache, true))
-+ return;
-+
-+ st = map.hva +
-+ offset_in_page(vcpu->arch.st.msr_val & KVM_STEAL_VALID_BITS);
-+
-+ st->preempted = vcpu->arch.st.steal.preempted = KVM_VCPU_PREEMPTED;
-
-- kvm_write_guest_offset_cached(vcpu->kvm, &vcpu->arch.st.stime,
-- &vcpu->arch.st.steal.preempted,
-- offsetof(struct kvm_steal_time, preempted),
-- sizeof(vcpu->arch.st.steal.preempted));
-+ kvm_unmap_gfn(vcpu, &map, &vcpu->arch.st.cache, true, true);
- }
-
- void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)