KVM: x86: race between KVM_SET_GSI_ROUTING and KVM_CREATE_IRQCHIP

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.

Also, as a side effect, this patch makes sure that KVM_SET_GSI_ROUTING
and KVM_CAP_SPLIT_IRQCHIP cannot run in parallel.

Signed-off-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index f489167..357e67c 100644 (file)
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -3069,8 +3069,11 @@ 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;