From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757946Ab3BRGNw (ORCPT ); Mon, 18 Feb 2013 01:13:52 -0500 Received: from szxga01-in.huawei.com ([119.145.14.64]:53167 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757531Ab3BRGNu (ORCPT ); Mon, 18 Feb 2013 01:13:50 -0500 Message-ID: <5121C68F.1000309@huawei.com> Date: Mon, 18 Feb 2013 14:13:35 +0800 From: Li Zefan User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:17.0) Gecko/20130107 Thunderbird/17.0.2 MIME-Version: 1.0 To: Tejun Heo CC: "Kirill A. Shutemov" , LKML , Cgroups Subject: [PATCH] cgroup: fail if monitored file and event_control are in different cgroup Content-Type: text/plain; charset="GB2312" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.135.68.215] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org If we pass fd of memory.usage_in_bytes of cgroup A to cgroup.event_control of cgroup B, then we won't get memory usage notification from A but B! What's worse, if A and B are in different mount hierarchy, we'll end up accessing NULL pointer! Disallow this kind of invalid usage. Signed-off-by: Li Zefan --- kernel/cgroup.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 65c8101..a41673c 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -3911,6 +3911,7 @@ static int cgroup_write_event_control(struct cgroup *cgrp, struct cftype *cft, const char *buffer) { struct cgroup_event *event = NULL; + struct cgroup *cgrp_cfile; unsigned int efd, cfd; struct file *efile = NULL; struct file *cfile = NULL; @@ -3966,6 +3967,16 @@ static int cgroup_write_event_control(struct cgroup *cgrp, struct cftype *cft, goto fail; } + /* + * The file to be monitored must be in the same cgroup as + * cgroup.event_control is. + */ + cgrp_cfile = __d_cgrp(cfile->f_dentry->d_parent); + if (cgrp_cfile != cgrp) { + ret = -EINVAL; + goto fail; + } + if (!event->cft->register_event || !event->cft->unregister_event) { ret = -EINVAL; goto fail; -- 1.8.0.2