KVM: lapic: Check for in-kernel LAPIC before deferencing apic pointer

...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+f7e65445a40d3e0e4ebf@syzkaller.appspotmail.com
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index e0fa6fc..bd13fdd 100644 (file)
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -1507,9 +1507,6 @@ void wait_lapic_expire(struct kvm_vcpu *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;
 

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 5762131..b5edc8e 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -7894,7 +7894,8 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
        }
 
        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();