[PATCH 5.0 103/122] KVM: lapic: Check for in-kernel LAPIC before deferencing apic pointer

[Greg Kroah-Hartman]

From: Sean Christopherson <sean.j.christopher...@intel.com>

commit b904cb8dff824b79233e82c078837627ebd52717 upstream.

...to avoid dereferencing a null pointer when querying the per-vCPU
timer advance.

Fixes: 39497d7660d98 ("KVM: lapic: Track lapic timer advance per vCPU")
Reported-by: syzbot+f7e65445a40d3e0e4...@syzkaller.appspotmail.com
Signed-off-by: Sean Christopherson <sean.j.christopher...@intel.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.w...@oracle.com>
Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 arch/x86/kvm/lapic.c |    3 ---
 arch/x86/kvm/x86.c   |    3 ++-
 2 files changed, 2 insertions(+), 4 deletions(-)

--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -1504,9 +1504,6 @@ void wait_lapic_expire(struct kvm_vcpu *
        u32 timer_advance_ns = apic->lapic_timer.timer_advance_ns;
        u64 guest_tsc, tsc_deadline, ns;
 
-       if (!lapic_in_kernel(vcpu))
-               return;
-
        if (apic->lapic_timer.expired_tscdeadline == 0)
                return;
 
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -7886,7 +7886,8 @@ static int vcpu_enter_guest(struct kvm_v
        }
 
        trace_kvm_entry(vcpu->vcpu_id);
-       if (vcpu->arch.apic->lapic_timer.timer_advance_ns)
+       if (lapic_in_kernel(vcpu) &&
+           vcpu->arch.apic->lapic_timer.timer_advance_ns)
                wait_lapic_expire(vcpu);
        guest_enter_irqoff();