From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932972AbcFQQ0a (ORCPT ); Fri, 17 Jun 2016 12:26:30 -0400 Received: from gum.cmpxchg.org ([85.214.110.215]:60144 "EHLO gum.cmpxchg.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932106AbcFQQ02 (ORCPT ); Fri, 17 Jun 2016 12:26:28 -0400 Date: Fri, 17 Jun 2016 12:23:59 -0400 From: Johannes Weiner To: Tejun Heo Cc: Andrew Morton , Vladimir Davydov , Michal Hocko , Li Zefan , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com Subject: [PATCH 1/3] cgroup: fix idr leak for the first cgroup root Message-ID: <20160617162359.GB19084@cmpxchg.org> References: <20160616034244.14839-1-hannes@cmpxchg.org> <20160616200617.GD3262@mtj.duckdns.org> <20160617162310.GA19084@cmpxchg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160617162310.GA19084@cmpxchg.org> User-Agent: Mutt/1.6.1 (2016-04-27) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The valid cgroup hierarchy ID range includes 0, so we can't filter for positive numbers when freeing it, or it'll leak the first ID. No big deal, just disruptive when reading the code. The ID is freed during error handling and when the reference count hits zero, so the double-free test is not necessary; remove it. Signed-off-by: Johannes Weiner --- kernel/cgroup.c | 8 +------- 1 file changed, 1 insertion(+), 7 deletions(-) diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 86cb5c6e8932..36fc0ff506c3 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -1158,18 +1158,12 @@ static void cgroup_exit_root_id(struct cgroup_root *root) { lockdep_assert_held(&cgroup_mutex); - if (root->hierarchy_id) { - idr_remove(&cgroup_hierarchy_idr, root->hierarchy_id); - root->hierarchy_id = 0; - } + idr_remove(&cgroup_hierarchy_idr, root->hierarchy_id); } static void cgroup_free_root(struct cgroup_root *root) { if (root) { - /* hierarchy ID should already have been released */ - WARN_ON_ONCE(root->hierarchy_id); - idr_destroy(&root->cgroup_idr); kfree(root); } -- 2.8.3