diff options
| author | Petr Malat <oss@malat.biz> | 2026-04-23 04:48:26 -0500 |
|---|---|---|
| committer | Tejun Heo <tj@kernel.org> | 2026-04-23 07:37:40 -1000 |
| commit | 13e786b64bd3fd81c7eb22aa32bf8305c32f2ccf (patch) | |
| tree | 737cdad0adf2c7a04691bcbf31dab67485785fc5 /kernel | |
| parent | 41d701ddc36d5301b44ea79529f3cf03c541c1e1 (diff) | |
cgroup: Increment nr_dying_subsys_* from rmdir context
Incrementing nr_dying_subsys_* in offline_css(), which is executed by
cgroup_offline_wq worker, leads to a race where user can see the value
to be 0 if he reads cgroup.stat after calling rmdir and before the worker
executes. This makes the user wrongly expect resources released by the
removed cgroup to be available for a new assignment.
Increment nr_dying_subsys_* from kill_css(), which is called from the
cgroup_rmdir() context.
Fixes: ab0312526867 ("cgroup: Show # of subsystem CSSes in cgroup.stat")
Signed-off-by: Petr Malat <oss@malat.biz>
Signed-off-by: Tejun Heo <tj@kernel.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/cgroup/cgroup.c | 22 |
1 files changed, 12 insertions, 10 deletions
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index 3243c2087ee3..c928dea9dea6 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -5724,16 +5724,6 @@ static void offline_css(struct cgroup_subsys_state *css) RCU_INIT_POINTER(css->cgroup->subsys[ss->id], NULL); wake_up_all(&css->cgroup->offline_waitq); - - css->cgroup->nr_dying_subsys[ss->id]++; - /* - * Parent css and cgroup cannot be freed until after the freeing - * of child css, see css_free_rwork_fn(). - */ - while ((css = css->parent)) { - css->nr_descendants--; - css->cgroup->nr_dying_subsys[ss->id]++; - } } /** @@ -6045,6 +6035,8 @@ static void css_killed_ref_fn(struct percpu_ref *ref) */ static void kill_css(struct cgroup_subsys_state *css) { + struct cgroup_subsys *ss = css->ss; + lockdep_assert_held(&cgroup_mutex); if (css->flags & CSS_DYING) @@ -6081,6 +6073,16 @@ static void kill_css(struct cgroup_subsys_state *css) * css is confirmed to be seen as killed on all CPUs. */ percpu_ref_kill_and_confirm(&css->refcnt, css_killed_ref_fn); + + css->cgroup->nr_dying_subsys[ss->id]++; + /* + * Parent css and cgroup cannot be freed until after the freeing + * of child css, see css_free_rwork_fn(). + */ + while ((css = css->parent)) { + css->nr_descendants--; + css->cgroup->nr_dying_subsys[ss->id]++; + } } /** |