Merge branch 'for-3.7-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

Pull cgroup fixes from Tejun Heo:
 "This contains two fix patches for device_cgroup.  One fixes a
  regression introduced earlier in 3.7 cycle where device_cgroup could
  try to dereference the NULL parent of the root cgroup.  The other one
  is RCU usage fix."

* 'for-3.7-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
  device_cgroup: fix RCU usage
  device_cgroup: fix unchecked cgroup parent usage

security/device_cgroup.c

@@ -164,8 +164,8 @@ static void dev_exception_clean(struct dev_cgroup *dev_cgroup)
 	struct dev_exception_item *ex, *tmp;
 
 	list_for_each_entry_safe(ex, tmp, &dev_cgroup->exceptions, list) {
-		list_del(&ex->list);
-		kfree(ex);
+		list_del_rcu(&ex->list);
+		kfree_rcu(ex, rcu);
 	}
 }
 
@@ -298,7 +298,7 @@ static int may_access(struct dev_cgroup *dev_cgroup,
 	struct dev_exception_item *ex;
 	bool match = false;
 
-	list_for_each_entry(ex, &dev_cgroup->exceptions, list) {
+	list_for_each_entry_rcu(ex, &dev_cgroup->exceptions, list) {
 		if ((refex->type & DEV_BLOCK) && !(ex->type & DEV_BLOCK))
 			continue;
 		if ((refex->type & DEV_CHAR) && !(ex->type & DEV_CHAR))
@@ -352,6 +352,8 @@ static int parent_has_perm(struct dev_cgroup *childcg,
  */
 static inline int may_allow_all(struct dev_cgroup *parent)
 {
+	if (!parent)
+		return 1;
 	return parent->behavior == DEVCG_DEFAULT_ALLOW;
 }
 
@@ -376,11 +378,14 @@ static int devcgroup_update_access(struct dev_cgroup *devcgroup,
 	int count, rc;
 	struct dev_exception_item ex;
 	struct cgroup *p = devcgroup->css.cgroup;
-	struct dev_cgroup *parent = cgroup_to_devcgroup(p->parent);
+	struct dev_cgroup *parent = NULL;
 
 	if (!capable(CAP_SYS_ADMIN))
 		return -EPERM;
 
+	if (p->parent)
+		parent = cgroup_to_devcgroup(p->parent);
+
 	memset(&ex, 0, sizeof(ex));
 	b = buffer;
 
@@ -391,11 +396,14 @@ static int devcgroup_update_access(struct dev_cgroup *devcgroup,
 			if (!may_allow_all(parent))
 				return -EPERM;
 			dev_exception_clean(devcgroup);
+			devcgroup->behavior = DEVCG_DEFAULT_ALLOW;
+			if (!parent)
+				break;
+
 			rc = dev_exceptions_copy(&devcgroup->exceptions,
 						 &parent->exceptions);
 			if (rc)
 				return rc;
-			devcgroup->behavior = DEVCG_DEFAULT_ALLOW;
 			break;
 		case DEVCG_DENY:
 			dev_exception_clean(devcgroup);