Revert "kobject: Remove redundant checks for whether ktype is NULL"

This reverts commit 1b28cb81.

It is reported to cause problems, so revert it for now until the root
cause can be found.
Reported-by: kernel test robot <oliver.sang@intel.com>
Fixes: 1b28cb81 ("kobject: Remove redundant checks for whether ktype is NULL")
Cc: Zhen Lei <thunder.leizhen@huawei.com>
Closes: https://lore.kernel.org/oe-lkp/202402071403.e302e33a-oliver.sang@intel.com
Link: https://lore.kernel.org/r/2024020849-consensus-length-6264@gregkhSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

lib/kobject.c

@@ -74,11 +74,13 @@ static int create_dir(struct kobject *kobj)
 	if (error)
 		return error;
 
+	if (ktype) {
 		error = sysfs_create_groups(kobj, ktype->default_groups);
 		if (error) {
 			sysfs_remove_dir(kobj);
 			return error;
 		}
+	}
 
 	/*
 	 * @kobj->sd may be deleted by an ancestor going away.  Hold an
@@ -589,6 +591,7 @@ static void __kobject_del(struct kobject *kobj)
 	sd = kobj->sd;
 	ktype = get_ktype(kobj);
 
+	if (ktype)
 		sysfs_remove_groups(kobj, ktype->default_groups);
 
 	/* send "remove" if the caller did not do it but sent "add" */
@@ -666,6 +669,10 @@ static void kobject_cleanup(struct kobject *kobj)
 	pr_debug("'%s' (%p): %s, parent %p\n",
 		 kobject_name(kobj), kobj, __func__, kobj->parent);
 
+	if (t && !t->release)
+		pr_debug("'%s' (%p): does not have a release() function, it is broken and must be fixed. See Documentation/core-api/kobject.rst.\n",
+			 kobject_name(kobj), kobj);
+
 	/* remove from sysfs if the caller did not do it */
 	if (kobj->state_in_sysfs) {
 		pr_debug("'%s' (%p): auto cleanup kobject_del\n",
@@ -676,13 +683,10 @@ static void kobject_cleanup(struct kobject *kobj)
 		parent = NULL;
 	}
 
-	if (t->release) {
+	if (t && t->release) {
 		pr_debug("'%s' (%p): calling ktype release\n",
 			 kobject_name(kobj), kobj);
 		t->release(kobj);
-	} else {
-		pr_debug("'%s' (%p): does not have a release() function, it is broken and must be fixed. See Documentation/core-api/kobject.rst.\n",
-			 kobject_name(kobj), kobj);
 	}
 
 	/* free name if we allocated it */
@@ -1056,7 +1060,7 @@ const struct kobj_ns_type_operations *kobj_child_ns_ops(const struct kobject *pa
 {
 	const struct kobj_ns_type_operations *ops = NULL;
 
-	if (parent && parent->ktype->child_ns_type)
+	if (parent && parent->ktype && parent->ktype->child_ns_type)
 		ops = parent->ktype->child_ns_type(parent);
 
 	return ops;