Jiang Jiasheng <jiasheng@xxxxxxxxxxx> writes: > The kvm_get_vcpu() will call for the array_index_nospec() > with the value of atomic_read(&(v->kvm)->online_vcpus) as size, > and the value of constant '0' as index. > If the size is also '0', it will be unreasonabe > that the index is no less than the size. > Can this really happen? 'online_vcpus' is never decreased, it is increased with every kvm_vm_ioctl_create_vcpu() call when a new vCPU is created and is set to 0 when all vCPUs are destroyed (kvm_free_vcpus()). kvm_guest_time_update() takes a vcpu as a parameter, this means that at least 1 vCPU is currently present so 'online_vcpus' just can't be zero. > Signed-off-by: Jiang Jiasheng <jiasheng@xxxxxxxxxxx> > --- > arch/x86/kvm/x86.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index e0f4a46..c59013c 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -2871,7 +2871,7 @@ static int kvm_guest_time_update(struct kvm_vcpu *v) > offsetof(struct compat_vcpu_info, time)); > if (vcpu->xen.vcpu_time_info_set) > kvm_setup_pvclock_page(v, &vcpu->xen.vcpu_time_info_cache, 0); > - if (v == kvm_get_vcpu(v->kvm, 0)) > + if (atomic_read(&(v->kvm)->online_vcpus) > 0 && v == kvm_get_vcpu(v->kvm, 0)) > kvm_hv_setup_tsc_page(v->kvm, &vcpu->hv_clock); > return 0; > } -- Vitaly
