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Commit 83ab0aa0 authored by Thomas Gleixner's avatar Thomas Gleixner
Browse files

sched: Don't use possibly stale sched_class 



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: default avatarThomas Gleixner <tglx@linutronix.de>
Acked-by: default avatarPeter Zijlstra <peterz@infradead.org>
Cc: stable@kernel.org
parent 6e40f5bb

kernel/sched.c

+4 −2
Original line number Original line Diff line number Diff line
@@ -4249,7 +4249,7 @@ void rt_mutex_setprio(struct task_struct *p, int prio) 
	unsigned long flags;

	unsigned long flags;

	int oldprio, on_rq, running;

	int oldprio, on_rq, running;

	struct rq *rq;

	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);

	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);

	update_rq_clock(rq);





	oldprio = p->prio;

	oldprio = p->prio;

	prev_class = p->sched_class;

	on_rq = p->se.on_rq;

	on_rq = p->se.on_rq;

	running = task_current(rq, p);

	running = task_current(rq, p);

	if (on_rq)

	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;

	int retval, oldprio, oldpolicy = -1, on_rq, running;

	unsigned long flags;

	unsigned long flags;

	const struct sched_class *prev_class = p->sched_class;

	const struct sched_class *prev_class;

	struct rq *rq;

	struct rq *rq;

	int reset_on_fork;

	int reset_on_fork;
@@ -4590,6 +4591,7 @@ static int __sched_setscheduler(struct task_struct *p, int policy, 
	p->sched_reset_on_fork = reset_on_fork;

	p->sched_reset_on_fork = reset_on_fork;





	oldprio = p->prio;

	oldprio = p->prio;

	prev_class = p->sched_class;

	__setscheduler(rq, p, policy, param->sched_priority);

	__setscheduler(rq, p, policy, param->sched_priority);





	if (running)

	if (running)