Merge "configfs: Fix use-after-free when accessing sd->s_dentry"

	if (sd) {

		/* Coordinate with configfs_readdir */

		spin_lock(&configfs_dirent_lock);

		/* Coordinate with configfs_attach_attr where will increase

		 * sd->s_count and update sd->s_dentry to new allocated one.

		 * Only set sd->dentry to null when this dentry is the only

		 * sd owner.

		/*

		 * Set sd->s_dentry to null only when this dentry is the

		 * one that is going to be killed.

		 * If not do so, configfs_d_iput may run just after

		 * configfs_attach_attr and set sd->s_dentry to null

		 * even it's still in use.

		 */

		if (atomic_read(&sd->s_count) <= 2)

		if (sd->s_dentry == dentry)

			sd->s_dentry = NULL;

		spin_unlock(&configfs_dirent_lock);