USB: make single lock for all usb dynamic id lists

There are a number of places where we accidentally pass in a constant
structure to later cast it off to a dynamic one, and then attempt to
grab a lock on it, which is not a good idea.  To help resolve this, move
the dynamic id lock out of the dynamic id structure for the driver and
into one single lock for all USB dynamic ids.  As this lock should never
have any real contention (it's only every accessed when a device is
added or removed, which is always serialized) there should not be any
difference except for some memory savings.

Note, this just converts the existing use of the dynamic id lock to the
new static lock, there is one place that is accessing the dynamic id
list without grabbing the lock, that will be fixed up in a follow-on
change.

Cc: Johan Hovold <[email protected]>
Cc: Herve Codina <[email protected]>
Cc: Rob Herring <[email protected]>
Cc: Alan Stern <[email protected]>
Cc: Grant Grundler <[email protected]>
Cc: Oliver Neukum <[email protected]>
Cc: Yajun Deng <[email protected]>
Cc: Douglas Anderson <[email protected]>
Cc: [email protected]
Link: https://lore.kernel.org/r/2024111322-kindly-finalist-d247@gregkh
Signed-off-by: Greg Kroah-Hartman <[email protected]>

drivers/usb/common/common.c

@@ -415,6 +415,9 @@ EXPORT_SYMBOL_GPL(usb_of_get_companion_dev);
 struct dentry *usb_debug_root;
 EXPORT_SYMBOL_GPL(usb_debug_root);
 
+DEFINE_MUTEX(usb_dynids_lock);
+EXPORT_SYMBOL_GPL(usb_dynids_lock);
+
 static int __init usb_common_init(void)
 {
 	usb_debug_root = debugfs_create_dir("usb", NULL);

drivers/usb/core/driver.c

@@ -95,9 +95,9 @@ ssize_t usb_store_new_id(struct usb_dynids *dynids,
 		}
 	}
 
-	spin_lock(&dynids->lock);
+	mutex_lock(&usb_dynids_lock);
 	list_add_tail(&dynid->node, &dynids->list);
-	spin_unlock(&dynids->lock);
+	mutex_unlock(&usb_dynids_lock);
 
 	retval = driver_attach(driver);
 
@@ -160,7 +160,7 @@ static ssize_t remove_id_store(struct device_driver *driver, const char *buf,
 	if (fields < 2)
 		return -EINVAL;
 
-	spin_lock(&usb_driver->dynids.lock);
+	guard(mutex)(&usb_dynids_lock);
 	list_for_each_entry_safe(dynid, n, &usb_driver->dynids.list, node) {
 		struct usb_device_id *id = &dynid->id;
 
@@ -171,7 +171,6 @@ static ssize_t remove_id_store(struct device_driver *driver, const char *buf,
 			break;
 		}
 	}
-	spin_unlock(&usb_driver->dynids.lock);
 	return count;
 }
 
@@ -220,27 +219,24 @@ static void usb_free_dynids(struct usb_driver *usb_drv)
 {
 	struct usb_dynid *dynid, *n;
 
-	spin_lock(&usb_drv->dynids.lock);
+	guard(mutex)(&usb_dynids_lock);
 	list_for_each_entry_safe(dynid, n, &usb_drv->dynids.list, node) {
 		list_del(&dynid->node);
 		kfree(dynid);
 	}
-	spin_unlock(&usb_drv->dynids.lock);
 }
 
 static const struct usb_device_id *usb_match_dynamic_id(struct usb_interface *intf,
 							struct usb_driver *drv)
 {
 	struct usb_dynid *dynid;
 
-	spin_lock(&drv->dynids.lock);
+	guard(mutex)(&usb_dynids_lock);
 	list_for_each_entry(dynid, &drv->dynids.list, node) {
 		if (usb_match_one_id(intf, &dynid->id)) {
-			spin_unlock(&drv->dynids.lock);
 			return &dynid->id;
 		}
 	}
-	spin_unlock(&drv->dynids.lock);
 	return NULL;
 }
 
@@ -1076,7 +1072,6 @@ int usb_register_driver(struct usb_driver *new_driver, struct module *owner,
 	new_driver->driver.owner = owner;
 	new_driver->driver.mod_name = mod_name;
 	new_driver->driver.dev_groups = new_driver->dev_groups;
-	spin_lock_init(&new_driver->dynids.lock);
 	INIT_LIST_HEAD(&new_driver->dynids.list);
 
 	retval = driver_register(&new_driver->driver);

drivers/usb/serial/bus.c

@@ -136,12 +136,11 @@ static void free_dynids(struct usb_serial_driver *drv)
 {
 	struct usb_dynid *dynid, *n;
 
-	spin_lock(&drv->dynids.lock);
+	guard(mutex)(&usb_dynids_lock);
 	list_for_each_entry_safe(dynid, n, &drv->dynids.list, node) {
 		list_del(&dynid->node);
 		kfree(dynid);
 	}
-	spin_unlock(&drv->dynids.lock);
 }
 
 const struct bus_type usb_serial_bus_type = {
@@ -157,7 +156,6 @@ int usb_serial_bus_register(struct usb_serial_driver *driver)
 	int retval;
 
 	driver->driver.bus = &usb_serial_bus_type;
-	spin_lock_init(&driver->dynids.lock);
 	INIT_LIST_HEAD(&driver->dynids.list);
 
 	retval = driver_register(&driver->driver);

drivers/usb/serial/usb-serial.c

@@ -706,14 +706,12 @@ static const struct usb_device_id *match_dynamic_id(struct usb_interface *intf,
 {
 	struct usb_dynid *dynid;
 
-	spin_lock(&drv->dynids.lock);
+	guard(mutex)(&usb_dynids_lock);
 	list_for_each_entry(dynid, &drv->dynids.list, node) {
 		if (usb_match_one_id(intf, &dynid->id)) {
-			spin_unlock(&drv->dynids.lock);
 			return &dynid->id;
 		}
 	}
-	spin_unlock(&drv->dynids.lock);
 	return NULL;
 }
 

include/linux/usb.h

@@ -1129,8 +1129,8 @@ static inline int usb_make_path(struct usb_device *dev, char *buf, size_t size)
 /* ----------------------------------------------------------------------- */
 
 /* Stuff for dynamic usb ids */
+extern struct mutex usb_dynids_lock;
 struct usb_dynids {
-	spinlock_t lock;
 	struct list_head list;
 };