From f169007b2773f285e098cb84c74aac0154d65ff7 Mon Sep 17 00:00:00 2001 From: Li Zefan Date: Mon, 18 Feb 2013 14:13:35 +0800 Subject: [PATCH] cgroup: fail if monitored file and event_control are in different cgroup 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 --- kernel/cgroup.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/kernel/cgroup.c b/kernel/cgroup.c index feda81487be4..b5c64327e712 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -3856,6 +3856,7 @@ 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; @@ -3911,6 +3912,16 @@ 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;