lib/kobject.c : Check ktype in kobject_add_internal

If someone calls kobject_init with null kobj_type, kobject_init can detect it. But it does not have a return value, it just dumps stack. In this case, a kobject_add after that will result in:
-->kobject_add_varg

    -->kobject_add_internal
     -->create_dir
      -->sysfs_create_dir
       -->sysfs_read_ns_type
        -->kobj_child_ns_ops

In the end, it will call ->ktype->child_ns_type directly and we have an oops.

Check ktype before really add a kobject.

---
 lib/kobject.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

index 85d5e9b..3ba6216 100644
@@ -164,6 +164,9 @@ static int kobject_add_internal(struct kobject *kobj)
 	if (!kobj)
 		return -ENOENT;
 
+	if (!kobj->ktype)
+		return -EINVAL;
+
 	if (!kobj->name || !kobj->name[0]) {
 		WARN(1, "kobject: (%p): attempted to be registered with empty "
 			 "name!\n", kobj);

1.7.5.1

But how can we add a kobject without a valid ktype?

At the most, I'd prefer to warn about this, much like we warn about not having a name, and not just returning an error without a hint as to what went wrong.

greg k-h