On 2017年12月18日 16:50, Paolo Bonzini wrote: > On 18/12/2017 09:30, David Hildenbrand wrote: >> The ugly thing in kvm_irqfd_assign() is that we access irqfd without >> holding a lock. I think that should rather be fixed than working around >> that issue. (e.g. lock() -> lookup again -> verify still in list -> >> unlock()) > > I wonder if it's even simpler: > > diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c > index f2ac53ab8243..17ed298bd66f 100644 > --- a/virt/kvm/eventfd.c > +++ b/virt/kvm/eventfd.c > @@ -387,7 +387,6 @@ kvm_irqfd_assign(struct kvm *kvm, struct kvm_irqfd *args) > > idx = srcu_read_lock(&kvm->irq_srcu); > irqfd_update(kvm, irqfd); > - srcu_read_unlock(&kvm->irq_srcu, idx); > > list_add_tail(&irqfd->list, &kvm->irqfds.items); > > @@ -420,10 +419,12 @@ kvm_irqfd_assign(struct kvm *kvm, struct kvm_irqfd *args) > irqfd->consumer.token, ret); > } > #endif > + srcu_read_unlock(&kvm->irq_srcu, idx); > > return 0; > > fail: > + /* irq_srcu is *not* held here. */ > if (irqfd->resampler) > irqfd_resampler_shutdown(irqfd); > > Hi Paolo: This patch still can't prevent from freeing struct irqfd in irq_shutdown() during assign irqfd. Once irqfd is added to kvm->irqfds.items list, deassign path can get irqfd and free it. -- Best regards Tianyu Lan
