irqbypass: Disallow NULL token

A NULL token is meaningless and can only lead to unintended problems.
Error on registration with a NULL token, ignore de-registrations with
a NULL token.
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

include/linux/irqbypass.h

@@ -34,7 +34,7 @@ struct irq_bypass_consumer;
 /**
  * struct irq_bypass_producer - IRQ bypass producer definition
  * @node: IRQ bypass manager private list management
- * @token: opaque token to match between producer and consumer
+ * @token: opaque token to match between producer and consumer (non-NULL)
  * @irq: Linux IRQ number for the producer device
  * @add_consumer: Connect the IRQ producer to an IRQ consumer (optional)
  * @del_consumer: Disconnect the IRQ producer from an IRQ consumer (optional)
@@ -60,7 +60,7 @@ struct irq_bypass_producer {
 /**
  * struct irq_bypass_consumer - IRQ bypass consumer definition
  * @node: IRQ bypass manager private list management
- * @token: opaque token to match between producer and consumer
+ * @token: opaque token to match between producer and consumer (non-NULL)
  * @add_producer: Connect the IRQ consumer to an IRQ producer
  * @del_producer: Disconnect the IRQ consumer from an IRQ producer
  * @stop: Perform any quiesce operations necessary prior to add/del (optional)

virt/lib/irqbypass.c

@@ -89,6 +89,9 @@ int irq_bypass_register_producer(struct irq_bypass_producer *producer)
 	struct irq_bypass_producer *tmp;
 	struct irq_bypass_consumer *consumer;
 
+	if (!producer->token)
+		return -EINVAL;
+
 	might_sleep();
 
 	if (!try_module_get(THIS_MODULE))
@@ -136,6 +139,9 @@ void irq_bypass_unregister_producer(struct irq_bypass_producer *producer)
 	struct irq_bypass_producer *tmp;
 	struct irq_bypass_consumer *consumer;
 
+	if (!producer->token)
+		return;
+
 	might_sleep();
 
 	if (!try_module_get(THIS_MODULE))
@@ -177,7 +183,8 @@ int irq_bypass_register_consumer(struct irq_bypass_consumer *consumer)
 	struct irq_bypass_consumer *tmp;
 	struct irq_bypass_producer *producer;
 
-	if (!consumer->add_producer || !consumer->del_producer)
+	if (!consumer->token ||
+	    !consumer->add_producer || !consumer->del_producer)
 		return -EINVAL;
 
 	might_sleep();
@@ -227,6 +234,9 @@ void irq_bypass_unregister_consumer(struct irq_bypass_consumer *consumer)
 	struct irq_bypass_consumer *tmp;
 	struct irq_bypass_producer *producer;
 
+	if (!consumer->token)
+		return;
+
 	might_sleep();
 
 	if (!try_module_get(THIS_MODULE))