Commit 10bf2f7e authored by Vladimir Davydov's avatar Vladimir Davydov Committed by Tejun Heo
Browse files

cgroup: fix fail path in cgroup_load_subsys() 



Calling cgroup_unload_subsys() from cgroup_load_subsys() after
online_css() failure will result in a NULL ptr dereference on attempt to
offline_css(), because online_css() only assigns css to cgroup on
success. Let's fix that by skipping calls to offline_css() and
css_free() in cgroup_unload_subsys() if there is no css, and freeing css
in cgroup_load_subsys() on online_css() failure.

Signed-off-by: default avatarVladimir Davydov <vdavydov@parallels.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarLi Zefan <lizefan@huawei.com>
parent 0be8669d

kernel/cgroup.c

+9 −3
Original line number Diff line number Diff line
@@ -4652,8 +4652,10 @@ int __init_or_module cgroup_load_subsys(struct cgroup_subsys *ss) 
	write_unlock(&css_set_lock);



	ret = online_css(css);

	if (ret)

	if (ret) {

		ss->css_free(css);

		goto err_unload;

	}



	/* success! */

	mutex_unlock(&cgroup_root_mutex);
@@ -4680,6 +4682,7 @@ EXPORT_SYMBOL_GPL(cgroup_load_subsys); 
void cgroup_unload_subsys(struct cgroup_subsys *ss)

{

	struct cgrp_cset_link *link;

	struct cgroup_subsys_state *css;



	BUG_ON(ss->module == NULL);
@@ -4693,7 +4696,9 @@ void cgroup_unload_subsys(struct cgroup_subsys *ss) 
	mutex_lock(&cgroup_mutex);

	mutex_lock(&cgroup_root_mutex);



	offline_css(cgroup_css(cgroup_dummy_top, ss));

	css = cgroup_css(cgroup_dummy_top, ss);

	if (css)

		offline_css(css);



	/* deassign the subsys_id */

	cgroup_subsys[ss->subsys_id] = NULL;
@@ -4720,7 +4725,8 @@ void cgroup_unload_subsys(struct cgroup_subsys *ss) 
	 * need to free before marking as null because ss->css_free needs

	 * the cgrp->subsys pointer to find their state.

	 */

	ss->css_free(cgroup_css(cgroup_dummy_top, ss));

	if (css)

		ss->css_free(css);

	RCU_INIT_POINTER(cgroup_dummy_top->subsys[ss->subsys_id], NULL);



	mutex_unlock(&cgroup_root_mutex);

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