From mboxrd@z Thu Jan 1 00:00:00 1970 From: Li Zefan Subject: [PATCH] cgroup: fail if monitored file and event_control are in different cgroup Date: Mon, 18 Feb 2013 14:13:35 +0800 Message-ID: <5121C68F.1000309@huawei.com> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: Sender: cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: text/plain; charset="us-ascii" To: Tejun Heo Cc: "Kirill A. Shutemov" , LKML , Cgroups 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