From bad34660344f37db8b55ce8bc139bddc7d83af1b Mon Sep 17 00:00:00 2001
From: Li Zefan <lizefan@huawei.com>
Date: Fri, 14 Feb 2014 16:54:28 +0800
Subject: [PATCH] cgroup: fix locking in cgroupstats_build()
css_set_lock has been converted to css_set_rwsem, and rwsem can't nest
inside rcu_read_lock.
Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
---
kernel/cgroup.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 15dcae74b510..5606c0f08d95 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -2995,6 +2995,8 @@ int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry)
kernfs_type(kn) != KERNFS_DIR)
return -EINVAL;
+ mutex_lock(&cgroup_mutex);
+
/*
* We aren't being called from kernfs and there's no guarantee on
* @kn->priv's validity. For this and css_tryget_from_dir(),
@@ -3002,10 +3004,12 @@ int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry)
*/
rcu_read_lock();
cgrp = rcu_dereference(kn->priv);
- if (!cgrp) {
+ if (!cgrp || cgroup_is_dead(cgrp)) {
rcu_read_unlock();
+ mutex_unlock(&cgroup_mutex);
return -ENOENT;
}
+ rcu_read_unlock();
css_task_iter_start(&cgrp->dummy_css, &it);
while ((tsk = css_task_iter_next(&it))) {
@@ -3030,7 +3034,7 @@ int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry)
}
css_task_iter_end(&it);
- rcu_read_unlock();
+ mutex_unlock(&cgroup_mutex);
return 0;
}
--
GitLab