From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Li Zefan , "Kirill A. Shutemov" , Tejun Heo , Weng Meiling Subject: [ 11/17] cgroup: fail if monitored file and event_control are in different cgroup Date: Sun, 29 Sep 2013 12:26:50 -0700 Message-Id: <20130929190757.915037902@linuxfoundation.org> In-Reply-To: <20130929190757.138351117@linuxfoundation.org> References: <20130929190757.138351117@linuxfoundation.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: 3.0-stable review patch. If anyone has any objections, please let me know. ------------------ From: Li Zefan commit f169007b2773f285e098cb84c74aac0154d65ff7 upstream. 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 Acked-by: Kirill A. Shutemov Signed-off-by: Tejun Heo Cc: Weng Meiling Signed-off-by: Greg Kroah-Hartman --- kernel/cgroup.c | 11 +++++++++++ 1 file changed, 11 insertions(+) --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -3498,6 +3498,7 @@ static int cgroup_write_event_control(st const char *buffer) { struct cgroup_event *event = NULL; + struct cgroup *cgrp_cfile; unsigned int efd, cfd; struct file *efile = NULL; struct file *cfile = NULL; @@ -3552,6 +3553,16 @@ static int cgroup_write_event_control(st 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;