wifi: iwlwifi: pcie: clean up device removal work

We shouldn't access the device if we don't hold a reference,
and if - after locking - we see that it has no bus, we also
can't do anything, in fact, pci_stop_and_remove_bus_device()
will be a no-op.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://msgid.link/20231207044813.6c0879e695f7.I1d3ce75ecad32a4cbf1b9dad61bfb7bc7821fdd9@changeidSigned-off-by: Johannes Berg <johannes.berg@intel.com>

drivers/net/wireless/intel/iwlwifi/pcie/trans.c

@@ -2107,18 +2107,29 @@ static void iwl_trans_pcie_removal_wk(struct work_struct *wk)
 		container_of(wk, struct iwl_trans_pcie_removal, work);
 	struct pci_dev *pdev = removal->pdev;
 	static char *prop[] = {"EVENT=INACCESSIBLE", NULL};
-	struct pci_bus *bus = pdev->bus;
+	struct pci_bus *bus;
+
+	pci_lock_rescan_remove();
+
+	bus = pdev->bus;
+	/* in this case, something else already removed the device */
+	if (!bus)
+		goto out;
 
 	dev_err(&pdev->dev, "Device gone - attempting removal\n");
+
 	kobject_uevent_env(&pdev->dev.kobj, KOBJ_CHANGE, prop);
-	pci_lock_rescan_remove();
-	pci_dev_put(pdev);
+
 	pci_stop_and_remove_bus_device(pdev);
-	if (removal->rescan && bus) {
+	pci_dev_put(pdev);
+
+	if (removal->rescan) {
 		if (bus->parent)
 			bus = bus->parent;
 		pci_rescan_bus(bus);
 	}
+
+out:
 	pci_unlock_rescan_remove();
 
 	kfree(removal);