sched: Don't use possibly stale sched_class (83ab0aa0) · Commits · 戴 / test

setscheduler() saves task->sched_class outside of the rq->lock held region for a check after the setscheduler changes have become effective. That might result in checking a stale value. rtmutex_setprio() has the same problem, though it is protected by p->pi_lock against setscheduler(), but for correctness sake (and to avoid bad examples) it needs to be fixed as well. Retrieve task->sched_class inside of the rq->lock held region. Signed-off-by:

Thomas Gleixner <tglx@linutronix.de> Acked-by:

Peter Zijlstra <peterz@infradead.org> Cc: stable@kernel.org

kernel/sched.c

+4 −2

Original line number	Diff line number	Diff line
		@@ -4249,7 +4249,7 @@ void rt_mutex_setprio(struct task_struct *p, int prio)
		unsigned long flags;
		int oldprio, on_rq, running;
		struct rq *rq;
		const struct sched_class *prev_class = p->sched_class;
		const struct sched_class *prev_class;

		BUG_ON(prio < 0 \|\| prio > MAX_PRIO);

		@@ -4257,6 +4257,7 @@ void rt_mutex_setprio(struct task_struct *p, int prio)
		update_rq_clock(rq);

		oldprio = p->prio;
		prev_class = p->sched_class;
		on_rq = p->se.on_rq;
		running = task_current(rq, p);
		if (on_rq)
		@@ -4476,7 +4477,7 @@ static int __sched_setscheduler(struct task_struct *p, int policy,
		{
		int retval, oldprio, oldpolicy = -1, on_rq, running;
		unsigned long flags;
		const struct sched_class *prev_class = p->sched_class;
		const struct sched_class *prev_class;
		struct rq *rq;
		int reset_on_fork;

		@@ -4590,6 +4591,7 @@ recheck:
		p->sched_reset_on_fork = reset_on_fork;

		oldprio = p->prio;
		prev_class = p->sched_class;
		__setscheduler(rq, p, policy, param->sched_priority);

		if (running)

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