diff options
| -rw-r--r-- | security/device_cgroup.c | 56 |
1 files changed, 18 insertions, 38 deletions
diff --git a/security/device_cgroup.c b/security/device_cgroup.c index dd0dc574d78d..e8aad69f0d69 100644 --- 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; @@ -445,34 +442,6 @@ 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 * @ex: new exception to be propagated @@ -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; } |