[PATCH 5.5 249/367] x86/KVM: Clean up hosts steal time structure

Greg Kroah-Hartman
2020-02-10T12:46:26Z

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

commit a6bd811f1209fe1c64c9f6fd578101d6436c6b6e upstream.

Now that we are mapping kvm_steal_time from the guest directly we
don't need keep a copy of it in kvm_vcpu_arch.st. The same is true
for the stime field.

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>
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/x86/include/asm/kvm_host.h | 3 +--
arch/x86/kvm/x86.c | 11 +++--------
2 files changed, 4 insertions(+), 10 deletions(-)

--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -685,10 +685,9 @@ struct kvm_vcpu_arch {
bool pvclock_set_guest_stopped_request;

struct {
+ u8 preempted;
u64 msr_val;
u64 last_steal;
- struct gfn_to_hva_cache stime;
- struct kvm_steal_time steal;
struct gfn_to_pfn_cache cache;
} st;

--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2611,7 +2611,7 @@ static void record_steal_time(struct kvm
if (xchg(&st->preempted, 0) & KVM_VCPU_FLUSH_TLB)
kvm_vcpu_flush_tlb(vcpu, false);

- vcpu->arch.st.steal.preempted = 0;
+ vcpu->arch.st.preempted = 0;

if (st->version & 1)
st->version += 1; /* first time write, random junk */
@@ -2795,11 +2795,6 @@ int kvm_set_msr_common(struct kvm_vcpu *
if (data & KVM_STEAL_RESERVED_MASK)
return 1;

- if (kvm_gfn_to_hva_cache_init(vcpu->kvm, &vcpu->arch.st.stime,
- data & KVM_STEAL_VALID_BITS,
- sizeof(struct kvm_steal_time)))
- return 1;
-
vcpu->arch.st.msr_val = data;

if (!(data & KVM_MSR_ENABLED))
@@ -3519,7 +3514,7 @@ static void kvm_steal_time_set_preempted
if (!(vcpu->arch.st.msr_val & KVM_MSR_ENABLED))
return;

- if (vcpu->arch.st.steal.preempted)
+ if (vcpu->arch.st.preempted)
return;

if (kvm_map_gfn(vcpu, vcpu->arch.st.msr_val >> PAGE_SHIFT, &map,
@@ -3529,7 +3524,7 @@ static void kvm_steal_time_set_preempted
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;
+ st->preempted = vcpu->arch.st.preempted = KVM_VCPU_PREEMPTED;

kvm_unmap_gfn(vcpu, &map, &vcpu->arch.st.cache, true, true);
}