From mboxrd@z Thu Jan 1 00:00:00 1970 From: Li Zefan Subject: [PATCH] cgroup: add lock validation in check_for_release() Date: Fri, 25 Jan 2013 15:10:09 +0800 Message-ID: <51022FD1.4080800@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 , LKML , Cgroups There was a long-standing bug that this function was called without any lock. Add a check to prevent similar issue. Signed-off-by: Li Zefan --- kernel/cgroup.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-) diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 776ff75..3d21adf 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -5028,13 +5028,20 @@ int cgroup_is_descendant(const struct cgroup *cgrp, struct task_struct *task) static void check_for_release(struct cgroup *cgrp) { - /* All of these checks rely on RCU to keep the cgroup - * structure alive */ + /* + * All of these checks rely on RCU or cgroup_mutex to keep the cgroup + * structure alive + */ + rcu_lockdep_assert(rcu_read_lock_held() || cgroup_lock_is_held(), + "check_for_release() called witout proper locking"); + if (cgroup_is_releasable(cgrp) && !atomic_read(&cgrp->count) && list_empty(&cgrp->children) && !cgroup_has_css_refs(cgrp)) { - /* Control Group is currently removeable. If it's not + /* + * Control Group is currently removable. If it's not * already queued for a userspace notification, queue - * it now */ + * it now + */ int need_schedule_work = 0; raw_spin_lock(&release_list_lock); if (!cgroup_is_removed(cgrp) && -- 1.8.0.2