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Commit bad34660 authored by Li Zefan's avatar Li Zefan Committed by Tejun Heo
Browse files

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: default avatarLi Zefan <lizefan@huawei.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 430af8ad

kernel/cgroup.c

+6 −2
Original line number Diff line number Diff line
@@ -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;

}