hw/pci: Have safer pcie_bus_realize() by checking error path

While pci_bus_realize() currently does not use the Error* argument,
it would be an error to leave pcie_bus_realize() setting bus->flags
if pci_bus_realize() had failed.

Fix by using a local Error* and return early (propagating the error)
if pci_bus_realize() failed.

Reported-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20210201153700.618946-1-philmd@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

Author: philmd

hw/pci/pci.c

@@ -132,8 +132,13 @@ static void pci_bus_realize(BusState *qbus, Error **errp)
 static void pcie_bus_realize(BusState *qbus, Error **errp)
 {
     PCIBus *bus = PCI_BUS(qbus);
+    Error *local_err = NULL;
 
-    pci_bus_realize(qbus, errp);
+    pci_bus_realize(qbus, &local_err);
+    if (local_err) {
+        error_propagate(errp, local_err);
+        return;
+    }
 
     /*
      * A PCI-E bus can support extended config space if it's the root