On Tue, Mar 14, 2017 at 02:34:29PM +0100, David Hildenbrand wrote: > Avoid races between KVM_SET_GSI_ROUTING and KVM_CREATE_IRQCHIP by taking > the kvm->lock when setting up routes. > > If KVM_CREATE_IRQCHIP fails, KVM_SET_GSI_ROUTING could have already set > up routes pointing at pic/ioapic, being silently removed already. > > Signed-off-by: David Hildenbrand <david@xxxxxxxxxx> > --- > virt/kvm/kvm_main.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index a17d787..ad0f8b2 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -3079,8 +3079,11 @@ static long kvm_vm_ioctl(struct file *filp, > routing.nr * sizeof(*entries))) > goto out_free_irq_routing; > } > + /* avoid races with KVM_CREATE_IRQCHIP on x86 */ > + mutex_lock(&kvm->lock); > r = kvm_set_irq_routing(kvm, entries, routing.nr, > routing.flags); > + mutex_unlock(&kvm->lock); > out_free_irq_routing: > vfree(entries); > break; > -- > 2.9.3 > Out of my curiousity: do we have a use case that these two operations might collapse (KVM_CREATE_IRQCHIP and KVM_SET_GSI_ROUTING)? Or is this patch only for the sake of security? Another thing to mention is that, I guess adding this lock will benefit KVM_CAP_SPLIT_IRQCHIP as well, maybe nice to mention it too in the commit message. No worth a repost for this single reason though. Thanks, -- peterx
