Merge branch 'cpuinit-delete' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg...

[cascardo/linux.git] / security / device_cgroup.c

diff --git a/security/device_cgroup.c b/security/device_cgroup.c
index dd0dc57..e8aad69 100644 (file)
--- a/security/device_cgroup.c
+++ b/security/device_cgroup.c
@@ -49,8 +49,6 @@ struct dev_cgroup {
        struct cgroup_subsys_state css;
        struct list_head exceptions;
        enum devcg_behavior behavior;
-       /* temporary list for pending propagation operations */
-       struct list_head propagate_pending;
 };
 
 static inline struct dev_cgroup *css_to_devcgroup(struct cgroup_subsys_state *s)
@@ -241,7 +239,6 @@ static struct cgroup_subsys_state *devcgroup_css_alloc(struct cgroup *cgroup)
        if (!dev_cgroup)
                return ERR_PTR(-ENOMEM);
        INIT_LIST_HEAD(&dev_cgroup->exceptions);
-       INIT_LIST_HEAD(&dev_cgroup->propagate_pending);
        dev_cgroup->behavior = DEVCG_DEFAULT_NONE;
 
        return &dev_cgroup->css;
@@ -444,34 +441,6 @@ static void revalidate_active_exceptions(struct dev_cgroup *devcg)
        }
 }
 
-/**
- * get_online_devcg - walks the cgroup tree and fills a list with the online
- *                   groups
- * @root: cgroup used as starting point
- * @online: list that will be filled with online groups
- *
- * Must be called with devcgroup_mutex held. Grabs RCU lock.
- * Because devcgroup_mutex is held, no devcg will become online or offline
- * during the tree walk (see devcgroup_online, devcgroup_offline)
- * A separated list is needed because propagate_behavior() and
- * propagate_exception() need to allocate memory and can block.
- */
-static void get_online_devcg(struct cgroup *root, struct list_head *online)
-{
-       struct cgroup *pos;
-       struct dev_cgroup *devcg;
-
-       lockdep_assert_held(&devcgroup_mutex);
-
-       rcu_read_lock();
-       cgroup_for_each_descendant_pre(pos, root) {
-               devcg = cgroup_to_devcgroup(pos);
-               if (is_devcg_online(devcg))
-                       list_add_tail(&devcg->propagate_pending, online);
-       }
-       rcu_read_unlock();
-}
-
 /**
  * propagate_exception - propagates a new exception to the children
  * @devcg_root: device cgroup that added a new exception
@@ -482,15 +451,24 @@ static void get_online_devcg(struct cgroup *root, struct list_head *online)
 static int propagate_exception(struct dev_cgroup *devcg_root,
                               struct dev_exception_item *ex)
 {
-       struct cgroup *root = devcg_root->css.cgroup;
-       struct dev_cgroup *devcg, *parent, *tmp;
+       struct cgroup *root = devcg_root->css.cgroup, *pos;
        int rc = 0;
-       LIST_HEAD(pending);
 
-       get_online_devcg(root, &pending);
+       rcu_read_lock();
 
-       list_for_each_entry_safe(devcg, tmp, &pending, propagate_pending) {
-               parent = cgroup_to_devcgroup(devcg->css.cgroup->parent);
+       cgroup_for_each_descendant_pre(pos, root) {
+               struct dev_cgroup *devcg = cgroup_to_devcgroup(pos);
+
+               /*
+                * Because devcgroup_mutex is held, no devcg will become
+                * online or offline during the tree walk (see on/offline
+                * methods), and online ones are safe to access outside RCU
+                * read lock without bumping refcnt.
+                */
+               if (!is_devcg_online(devcg))
+                       continue;
+
+               rcu_read_unlock();
 
                /*
                 * in case both root's behavior and devcg is allow, a new
@@ -512,8 +490,10 @@ static int propagate_exception(struct dev_cgroup *devcg_root,
                }
                revalidate_active_exceptions(devcg);
 
-               list_del_init(&devcg->propagate_pending);
+               rcu_read_lock();
        }
+
+       rcu_read_unlock();
        return rc;
 }