From ed45b3440ffe515828a38fce2e397e85514eb93b Mon Sep 17 00:00:00 2001 From: Xiu Jianfeng <xiujianfeng@huawei.com> Date: Sat, 12 Oct 2024 07:22:46 +0000 Subject: [PATCH] cgroup: Fix potential overflow issue when checking max_depth MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit [ Upstream commit 3cc4e13bb1617f6a13e5e6882465984148743cf4 ] 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: 1a926e0bbab8 ("cgroup: implement hierarchy limits") Signed-off-by: Xiu Jianfeng <xiujianfeng@huawei.com> Reviewed-by: Michal Koutný <mkoutny@suse.com> Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org> --- kernel/cgroup/cgroup.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index 8d93b8ec1..3f96d0f9e 100755 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -5497,7 +5497,7 @@ 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); @@ -5505,7 +5505,7 @@ 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++;