xen/pirq: fix error path cleanup when binding MSIs

Current cleanup in the error path of xen_bind_pirq_msi_to_irq is
wrong. First of all there's an off-by-one in the cleanup loop, which
can lead to unbinding wrong IRQs.

Secondly IRQs not bound won't be freed, thus leaking IRQ numbers.

Note that there's no need to differentiate between bound and unbound
IRQs when freeing them, __unbind_from_irq will deal with both of them
correctly.

Fixes: 4892c9b ("xen: add support for MSI message groups")
Reported-by: Hooman Mirhadi <[email protected]>
Signed-off-by: Roger Pau Monné <[email protected]>
Reviewed-by: Amit Shah <[email protected]>
Reviewed-by: Boris Ostrovsky <[email protected]>
Signed-off-by: Juergen Gross <[email protected]>

Author: royger

drivers/xen/events/events_base.c

@@ -755,8 +755,8 @@ int xen_bind_pirq_msi_to_irq(struct pci_dev *dev, struct msi_desc *msidesc,
 	mutex_unlock(&irq_mapping_update_lock);
 	return irq;
 error_irq:
-	for (; i >= 0; i--)
-		__unbind_from_irq(irq + i);
+	while (nvec--)
+		__unbind_from_irq(irq + nvec);
 	mutex_unlock(&irq_mapping_update_lock);
 	return ret;
 }