vfio/pci: WARN_ON driver_override kasprintf failure

kasprintf() returns a pointer to dynamically allocated memory
which can be NULL upon failure.

This is a blocking notifier callback, so errno isn't a proper return
value. Use WARN_ON to small allocation failures.
Signed-off-by: Kunwu Chan <chentao@kylinos.cn>
Link: https://lore.kernel.org/r/20240115063434.20278-1-chentao@kylinos.cnSigned-off-by: Alex Williamson <alex.williamson@redhat.com>

drivers/vfio/pci/vfio_pci_core.c

@@ -2047,6 +2047,7 @@ static int vfio_pci_bus_notifier(struct notifier_block *nb,
 			 pci_name(pdev));
 		pdev->driver_override = kasprintf(GFP_KERNEL, "%s",
 						  vdev->vdev.ops->name);
+		WARN_ON(!pdev->driver_override);
 	} else if (action == BUS_NOTIFY_BOUND_DRIVER &&
 		   pdev->is_virtfn && physfn == vdev->pdev) {
 		struct pci_driver *drv = pci_dev_driver(pdev);