binderfs: add new binder devices to binder_devices

When binderfs is not enabled, the binder driver parses the kernel
config to create all binder devices. All of the new binder devices
are stored in the list binder_devices.

When binderfs is enabled, the binder driver creates new binder devices
dynamically when userspace applications call BINDER_CTL_ADD ioctl. But
the devices created in this way are not stored in the same list.

This patch fixes that.

Signed-off-by: Li Li <dualli@google.com>
Acked-by: Carlos Llamas <cmllamas@google.com>
Link: https://lore.kernel.org/r/20241218212935.4162907-2-dualli@chromium.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: eggonlea

drivers/android/binder.c

@@ -6928,6 +6928,11 @@ const struct binder_debugfs_entry binder_debugfs_entries[] = {
 	{} /* terminator */
 };
 
+void binder_add_device(struct binder_device *device)
+{
+	hlist_add_head(&device->hlist, &binder_devices);
+}
+
 static int __init init_binder_device(const char *name)
 {
 	int ret;

drivers/android/binder_internal.h

@@ -25,8 +25,7 @@ struct binder_context {
 
 /**
  * struct binder_device - information about a binder device node
- * @hlist:          list of binder devices (only used for devices requested via
- *                  CONFIG_ANDROID_BINDER_DEVICES)
+ * @hlist:          list of binder devices
  * @miscdev:        information about a binder character device node
  * @context:        binder context information
  * @binderfs_inode: This is the inode of the root dentry of the super block
@@ -582,4 +581,12 @@ struct binder_object {
 	};
 };
 
+/**
+ * Add a binder device to binder_devices
+ * @device: the new binder device to add to the global list
+ *
+ * Not reentrant as the list is not protected by any locks
+ */
+void binder_add_device(struct binder_device *device);
+
 #endif /* _LINUX_BINDER_INTERNAL_H */

drivers/android/binderfs.c

@@ -207,6 +207,8 @@ static int binderfs_binder_device_create(struct inode *ref_inode,
 	fsnotify_create(root->d_inode, dentry);
 	inode_unlock(d_inode(root));
 
+	binder_add_device(device);
+
 	return 0;
 
 err: