cgroup: fix harmless bugs in cgroup_load_subsys() fail path and cgroup_unload_subsys()

* If idr init fails, cgroup_load_subsys() cleared dummytop->subsys[]
  before calilng ->destroy() making CSS inaccessible to the callback,
  and didn't unlink ss->sibling.  As no modular controller uses
  ->use_id, this doesn't cause any actual problems.

* cgroup_unload_subsys() was forgetting to free idr, call
  ->pre_destroy() and clear ->active.  As there currently is no
  modular controller which uses ->use_id, ->pre_destroy() or ->active,
  this doesn't cause any actual problems.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>

1 files changed, 14 insertions, 1 deletions

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 09751657abdc..5679cb1ce43f 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -4420,9 +4420,10 @@ int __init_or_module cgroup_load_subsys(struct cgroup_subsys *ss)
         if (ss->use_id) {
                 int ret = cgroup_init_idr(ss, css);
                 if (ret) {
-                        dummytop->subsys[ss->subsys_id] = NULL;
                         ss->destroy(dummytop);
+                        dummytop->subsys[ss->subsys_id] = NULL;
                         subsys[ss->subsys_id] = NULL;
+                        list_del_init(&ss->sibling);
                         mutex_unlock(&cgroup_mutex);
                         return ret;
                 }
@@ -4490,7 +4491,19 @@ void cgroup_unload_subsys(struct cgroup_subsys *ss)
          */
         BUG_ON(ss->root != &rootnode);
 
+        /* ->pre_destroy() should be called outside cgroup_mutex for now */
+        if (ss->pre_destroy)
+                ss->pre_destroy(dummytop);
+
         mutex_lock(&cgroup_mutex);
+
+        ss->active = 0;
+
+        if (ss->use_id) {
+                idr_remove_all(&ss->idr);
+                idr_destroy(&ss->idr);
+        }
+
         /* deassign the subsys_id */
         subsys[ss->subsys_id] = NULL;