staging: rtl8192u: fix rmmod warn when device is renamed

This driver creates 4 debug files under [devname] folder. The devname
could be wlan0 initially, however it could be renamed later to e.g.
enx00e04c00000. This will cause problem during debug file teardown since
it uses netdev->name, which is no longer wlan0. To solve this problem,
add a notifier to handle device renaming. Also note that we cannot
simply do debugfs_lookup to find out old dentry since by the time the
notifier is called, netdev->name is already changed to new name.

Reported-by: Zheyu Ma <zheyuma97@gmail.com>
Tested-by: Zheyu Ma <zheyuma97@gmail.com>
Reviewed-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Tong Zhang <ztong0001@gmail.com>
Link: https://lore.kernel.org/r/20220730033335.74153-5-ztong0001@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtl8192u/r8192U.h

@@ -1122,6 +1122,7 @@ void setKey(struct net_device *dev, u8 EntryNo, u8 KeyIndex, u16 KeyType,
 
 void rtl8192_debugfs_init_one(struct net_device *dev);
 void rtl8192_debugfs_exit_one(struct net_device *dev);
+void rtl8192_debugfs_rename_one(struct net_device *dev);
 void rtl8192_debugfs_init(void);
 void rtl8192_debugfs_exit(void);
 

drivers/staging/rtl8192u/r8192U_core.c

@@ -4606,6 +4606,30 @@ static void rtl8192_usb_disconnect(struct usb_interface *intf)
 	RT_TRACE(COMP_DOWN, "wlan driver removed\n");
 }
 
+static int rtl8192_usb_netdev_event(struct notifier_block *nb, unsigned long event,
+				    void *data)
+{
+	struct net_device *netdev = netdev_notifier_info_to_dev(data);
+
+	if (netdev->netdev_ops != &rtl8192_netdev_ops)
+		goto out;
+
+	switch (event) {
+	case NETDEV_CHANGENAME:
+		rtl8192_debugfs_rename_one(netdev);
+		break;
+	default:
+		break;
+	}
+
+out:
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block rtl8192_usb_netdev_notifier = {
+	.notifier_call = rtl8192_usb_netdev_event,
+};
+
 static int __init rtl8192_usb_module_init(void)
 {
 	int ret;
@@ -4615,6 +4639,12 @@ static int __init rtl8192_usb_module_init(void)
 	RT_TRACE(COMP_INIT, "Initializing module");
 	RT_TRACE(COMP_INIT, "Wireless extensions version %d", WIRELESS_EXT);
 
+	ret = register_netdevice_notifier(&rtl8192_usb_netdev_notifier);
+	if (ret) {
+		pr_err("register_netdevice_notifier failed %d\n", ret);
+		return ret;
+	}
+
 	rtl8192_debugfs_init();
 	ret = ieee80211_debug_init();
 	if (ret) {
@@ -4663,6 +4693,7 @@ debug_exit:
 	ieee80211_debug_exit();
 debugfs_exit:
 	rtl8192_debugfs_exit();
+	unregister_netdevice_notifier(&rtl8192_usb_netdev_notifier);
 	return ret;
 }
 
@@ -4675,6 +4706,7 @@ static void __exit rtl8192_usb_module_exit(void)
 	ieee80211_crypto_deinit();
 	ieee80211_debug_exit();
 	rtl8192_debugfs_exit();
+	unregister_netdevice_notifier(&rtl8192_usb_netdev_notifier);
 	RT_TRACE(COMP_DOWN, "Exiting");
 }
 

drivers/staging/rtl8192u/r8192U_debugfs.c

@@ -169,6 +169,14 @@ void rtl8192_debugfs_exit_one(struct net_device *dev)
 	debugfs_remove_recursive(priv->debugfs_dir);
 }
 
+void rtl8192_debugfs_rename_one(struct net_device *dev)
+{
+	struct r8192_priv *priv = ieee80211_priv(dev);
+	struct dentry *parent_dir = debugfs_lookup(KBUILD_MODNAME, NULL);
+
+	debugfs_rename(parent_dir, priv->debugfs_dir, parent_dir, dev->name);
+}
+
 void rtl8192_debugfs_init(void)
 {
 	debugfs_create_dir(KBUILD_MODNAME, NULL);