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cgroup: Fix potential overflow issue when checking max_depth

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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: 1a926e0bba ("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>
This commit is contained in:
Xiu Jianfeng 2024-10-12 07:22:46 +00:00 committed by Tejun Heo
parent 117932eea9
commit 3cc4e13bb1
1 changed files with 2 additions and 2 deletions
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4
kernel/cgroup/cgroup.c
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@ -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++;