Commit 3cc4e13b authored by Xiu Jianfeng's avatar Xiu Jianfeng Committed by Tejun Heo
Browse files

cgroup: Fix potential overflow issue when checking max_depth 



cgroup.max.depth is the maximum allowed descent depth below the current
cgroup. If the actual descent depth is equal or larger, an attempt to
create a new child cgroup will fail. However due to the cgroup->max_depth
is of int type and having the default value INT_MAX, the condition
'level > cgroup->max_depth' will never be satisfied, and it will cause
an overflow of the level after it reaches to INT_MAX.

Fix it by starting the level from 0 and using '>=' instead.

It's worth mentioning that this issue is unlikely to occur in reality,
as it's impossible to have a depth of INT_MAX hierarchy, but should be
be avoided logically.

Fixes: 1a926e0b ("cgroup: implement hierarchy limits")
Signed-off-by: default avatarXiu Jianfeng <xiujianfeng@huawei.com>
Reviewed-by: default avatarMichal Koutný <mkoutny@suse.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 117932ee

kernel/cgroup/cgroup.c

+2 −2
Original line number Diff line number Diff line
@@ -5789,7 +5789,7 @@ static bool cgroup_check_hierarchy_limits(struct cgroup *parent) 
{

	struct cgroup *cgroup;

	int ret = false;

	int level = 1;

	int level = 0;



	lockdep_assert_held(&cgroup_mutex);
@@ -5797,7 +5797,7 @@ static bool cgroup_check_hierarchy_limits(struct cgroup *parent) 
		if (cgroup->nr_descendants >= cgroup->max_descendants)

			goto fail;



		if (level > cgroup->max_depth)

		if (level >= cgroup->max_depth)

			goto fail;



		level++;