sched: Fix throttle offline task trigger panic

hulk inclusion
category: bugfix
bugzilla: 51828, https://gitee.com/openeuler/kernel/issues/I4K96G
CVE: NA

--------------------------------

offline task invokes sched_setscheduler interface to change the
scheduling policy to SCHED_OTHER, trigger a system panic.
Signed-off-by: NZheng Zucheng <zhengzucheng@huawei.com>
Reviewed-by: NChen Hui <judy.chenhui@huawei.com>
Reviewed-by: NXiu Jianfeng <xiujianfeng@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

kernel/sched/core.c

@@ -4333,6 +4333,18 @@ static int __sched_setscheduler(struct task_struct *p,
 	}
 change:
 
+#ifdef CONFIG_QOS_SCHED
+	/*
+	 * If the scheduling policy of an offline task is set to a policy
+	 * other than SCHED_IDLE, the online task preemption will be invalid,
+	 * so return -EINVAL in this case.
+	 */
+	if (unlikely(task_group(p)->qos_level == -1 && !idle_policy(policy))) {
+		task_rq_unlock(rq, p, &rf);
+		return -EINVAL;
+	}
+#endif
+
 	if (user) {
 #ifdef CONFIG_RT_GROUP_SCHED
 		/*

kernel/sched/fair.c

@@ -6991,7 +6991,8 @@ static bool check_qos_cfs_rq(struct cfs_rq *cfs_rq)
 		return false;
 
 	if (cfs_rq && cfs_rq->tg->qos_level < 0 &&
-	    !sched_idle_cpu(cpu_of(rq_of(cfs_rq)))) {
+	    !sched_idle_cpu(cpu_of(rq_of(cfs_rq))) &&
+	     cfs_rq->h_nr_running == cfs_rq->idle_h_nr_running) {
 		throttle_qos_cfs_rq(cfs_rq);
 		return true;
 	}