sched_ext: Unregister sub_kset on scheduler disable

When ops.sub_attach is set, scx_alloc_and_add_sched() creates sub_kset as a
child of &sch->kobj, which pins the parent with its own reference. The
disable paths never call kset_unregister(), so the final kobject_put() in
bpf_scx_unreg() leaves a stale reference and scx_kobj_release() never runs,
leaking the whole struct scx_sched on every load/unload cycle.

Unregister sub_kset in scx_root_disable() and scx_sub_disable() before
kobject_del(&sch->kobj).

Fixes: ebeca1f930ea ("sched_ext: Introduce cgroup sub-sched support")
Reported-by: Chris Mason <clm@meta.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>

diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index 34de1c9b7a7c688c9f0a4a67a6c593e2f5e3bcde..7f991ecb1398756b34a6a9c1393f7ecf2c2465dd 100644 (file)
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -5721,6 +5721,8 @@ static void scx_sub_disable(struct scx_sched *sch)
 
        if (sch->ops.exit)
                SCX_CALL_OP(sch, exit, NULL, sch->exit_info);
+       if (sch->sub_kset)
+               kset_unregister(sch->sub_kset);
        kobject_del(&sch->kobj);
 }
 #else  /* CONFIG_EXT_SUB_SCHED */
@@ -5852,6 +5854,10 @@ static void scx_root_disable(struct scx_sched *sch)
         * could observe an object of the same name still in the hierarchy when
         * the next scheduler is loaded.
         */
+#ifdef CONFIG_EXT_SUB_SCHED
+       if (sch->sub_kset)
+               kset_unregister(sch->sub_kset);
+#endif
        kobject_del(&sch->kobj);
 
        free_kick_syncs();