2 files changed, 44 insertions, 35 deletions

diff --git a/drivers/usb/gadget/function/f_subset.c b/drivers/usb/gadget/function/f_subset.c
index a404c11acac6..638e3138f8a0 100644
--- a/drivers/usb/gadget/function/f_subset.c
+++ b/drivers/usb/gadget/function/f_subset.c
@@ -299,25 +299,22 @@ geth_bind(struct usb_configuration *c, struct usb_function *f)
 	struct usb_ep		*ep;
 
 	struct f_gether_opts	*gether_opts;
+	struct net_device	*net __free(detach_gadget) = NULL;
 
 	gether_opts = container_of(f->fi, struct f_gether_opts, func_inst);
 
-	/*
-	 * in drivers/usb/gadget/configfs.c:configfs_composite_bind()
-	 * configurations are bound in sequence with list_for_each_entry,
-	 * in each configuration its functions are bound in sequence
-	 * with list_for_each_entry, so we assume no race condition
-	 * with regard to gether_opts->bound access
-	 */
-	if (!gether_opts->bound) {
-		mutex_lock(&gether_opts->lock);
-		gether_set_gadget(gether_opts->net, cdev->gadget);
-		status = gether_register_netdev(gether_opts->net);
-		mutex_unlock(&gether_opts->lock);
-		if (status)
-			return status;
-		gether_opts->bound = true;
-	}
+	scoped_guard(mutex, &gether_opts->lock)
+		if (gether_opts->bind_count == 0 && !gether_opts->bound) {
+			if (!device_is_registered(&gether_opts->net->dev)) {
+				gether_set_gadget(gether_opts->net, cdev->gadget);
+				status = gether_register_netdev(gether_opts->net);
+			} else
+				status = gether_attach_gadget(gether_opts->net, cdev->gadget);
+
+			if (status)
+				return status;
+			net = gether_opts->net;
+		}
 
 	us = usb_gstrings_attach(cdev, geth_strings,
 				 ARRAY_SIZE(geth_string_defs));
@@ -330,20 +327,18 @@ geth_bind(struct usb_configuration *c, struct usb_function *f)
 	/* allocate instance-specific interface IDs */
 	status = usb_interface_id(c, f);
 	if (status < 0)
-		goto fail;
+		return status;
 	subset_data_intf.bInterfaceNumber = status;
 
-	status = -ENODEV;
-
 	/* allocate instance-specific endpoints */
 	ep = usb_ep_autoconfig(cdev->gadget, &fs_subset_in_desc);
 	if (!ep)
-		goto fail;
+		return -ENODEV;
 	geth->port.in_ep = ep;
 
 	ep = usb_ep_autoconfig(cdev->gadget, &fs_subset_out_desc);
 	if (!ep)
-		goto fail;
+		return -ENODEV;
 	geth->port.out_ep = ep;
 
 	/* support all relevant hardware speeds... we expect that when
@@ -361,21 +356,19 @@ geth_bind(struct usb_configuration *c, struct usb_function *f)
 	status = usb_assign_descriptors(f, fs_eth_function, hs_eth_function,
 			ss_eth_function, ss_eth_function);
 	if (status)
-		goto fail;
+		return status;
 
 	/* NOTE:  all that is done without knowing or caring about
 	 * the network link ... which is unavailable to this code
 	 * until we're activated via set_alt().
 	 */
 
+	gether_opts->bind_count++;
+	retain_and_null_ptr(net);
+
 	DBG(cdev, "CDC Subset: IN/%s OUT/%s\n",
 			geth->port.in_ep->name, geth->port.out_ep->name);
 	return 0;
-
-fail:
-	ERROR(cdev, "%s: can't bind, err %d\n", f->name, status);
-
-	return status;
 }
 
 static inline struct f_gether_opts *to_f_gether_opts(struct config_item *item)
@@ -418,7 +411,7 @@ static void geth_free_inst(struct usb_function_instance *f)
 	struct f_gether_opts *opts;
 
 	opts = container_of(f, struct f_gether_opts, func_inst);
-	if (opts->bound)
+	if (device_is_registered(&opts->net->dev))
 		gether_cleanup(netdev_priv(opts->net));
 	else
 		free_netdev(opts->net);
@@ -462,8 +455,16 @@ static void geth_free(struct usb_function *f)
 
 static void geth_unbind(struct usb_configuration *c, struct usb_function *f)
 {
+	struct f_gether_opts *opts;
+
+	opts = container_of(f->fi, struct f_gether_opts, func_inst);
+
 	geth_string_defs[0].id = 0;
 	usb_free_all_descriptors(f);
+
+	opts->bind_count--;
+	if (opts->bind_count == 0 && !opts->bound)
+		gether_detach_gadget(opts->net);
 }
 
 static struct usb_function *geth_alloc(struct usb_function_instance *fi)
diff --git a/drivers/usb/gadget/function/u_gether.h b/drivers/usb/gadget/function/u_gether.h
index 2f7a373ed449..e7b6b51f69c1 100644
--- a/drivers/usb/gadget/function/u_gether.h
+++ b/drivers/usb/gadget/function/u_gether.h
@@ -15,17 +15,25 @@
 
 #include <linux/usb/composite.h>
 
+/**
+ * struct f_gether_opts - subset function options
+ * @func_inst: USB function instance.
+ * @net: The net_device associated with the subset function.
+ * @bound: True if the net_device is shared and pre-registered during the
+ *         legacy composite driver's bind phase (e.g., multi.c). If false,
+ *         the subset function will register the net_device during its own
+ *         bind phase.
+ * @bind_count: Tracks the number of configurations the subset function is
+ *              bound to, preventing double-registration of the @net device.
+ * @lock: Protects the data from concurrent access by configfs read/write
+ *        and create symlink/remove symlink operations.
+ * @refcnt: Reference counter for the function instance.
+ */
 struct f_gether_opts {
 	struct usb_function_instance	func_inst;
 	struct net_device		*net;
 	bool				bound;
-
-	/*
-	 * Read/write access to configfs attributes is handled by configfs.
-	 *
-	 * This is to protect the data from concurrent access by read/write
-	 * and create symlink/remove symlink.
-	 */
+	int				bind_count;
 	struct mutex			lock;
 	int				refcnt;
 };