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authorLi Zefan <lizefan@huawei.com>2013-02-18 14:13:35 +0800
committerTejun Heo <tj@kernel.org>2013-02-18 09:31:35 -0800
commitf169007b2773f285e098cb84c74aac0154d65ff7 (patch)
tree6b295320c25b9fe8c1e4e94fcc35570134ebb8be
parent810cbee4fad570ff167132d4ecf247d99c48f71d (diff)
downloadvexpress-lsk-f169007b2773f285e098cb84c74aac0154d65ff7.tar.gz
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 <lizefan@huawei.com> Acked-by: Kirill A. Shutemov <kirill@shutemov.name> Signed-off-by: Tejun Heo <tj@kernel.org>
-rw-r--r--kernel/cgroup.c11
1 files changed, 11 insertions, 0 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index feda81487be..b5c64327e71 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;