mm/slub: fix slab double-free in case of duplicate sysfs filename

sysfs_slab_add() shouldn't call kobject_put at error path: this puts last
reference of kmem-cache kobject and frees it.  Kmem cache will be freed
second time at error path in kmem_cache_create().

For example this happens when slub debug was enabled in runtime and
somebody creates new kmem cache:

# echo 1 | tee /sys/kernel/slab/*/sanity_checks
# modprobe configfs

"configfs_dir_cache" cannot be merged because existing slab have debug and
cannot create new slab because unique name ":t-0000096" already taken.

Signed-off-by: Konstantin Khlebnikov <[email protected]>
Acked-by: Christoph Lameter <[email protected]>
Cc: Pekka Enberg <[email protected]>
Acked-by: David Rientjes <[email protected]>
Cc: Joonsoo Kim <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

mm/slub.c

@@ -5283,7 +5283,7 @@ static int sysfs_slab_add(struct kmem_cache *s)
 	s->kobj.kset = cache_kset(s);
 	err = kobject_init_and_add(&s->kobj, &slab_ktype, NULL, "%s", name);
 	if (err)
-		goto out_put_kobj;
+		goto out;
 
 	err = sysfs_create_group(&s->kobj, &slab_attr_group);
 	if (err)
@@ -5310,8 +5310,6 @@ out:
 	return err;
 out_del_kobj:
 	kobject_del(&s->kobj);
-out_put_kobj:
-	kobject_put(&s->kobj);
 	goto out;
 }