From: Thomas Gleixner <tglx@linutronix.de>
To: Lukas Wunner <lukas@wunner.de>
Cc: Bjorn Helgaas <bhelgaas@google.com>,
Mika Westerberg <mika.westerberg@linux.intel.com>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org
Subject: Re: [PATCH] genirq: Synchronize only with single thread on free_irq()
Date: Thu, 21 Jun 2018 22:21:44 +0200 (CEST) [thread overview]
Message-ID: <alpine.DEB.2.21.1806212217571.1591@nanos.tec.linutronix.de> (raw)
In-Reply-To: <8f770886632640321592873e4c902218d42c436b.1527194314.git.lukas@wunner.de>
On Thu, 24 May 2018, Lukas Wunner wrote:
> static int irq_wait_for_interrupt(struct irqaction *action)
> {
> - set_current_state(TASK_INTERRUPTIBLE);
> + for (;;) {
> + set_current_state(TASK_INTERRUPTIBLE);
>
> - while (!kthread_should_stop()) {
> + if (kthread_should_stop()) {
> + /* may need to run one last time. */
> + if (test_and_clear_bit(IRQTF_RUNTHREAD,
> + &action->thread_flags)) {
> + __set_current_state(TASK_RUNNING);
> + return 0;
> + }
> + __set_current_state(TASK_RUNNING);
> + return -1;
> + }
>
> if (test_and_clear_bit(IRQTF_RUNTHREAD,
> &action->thread_flags)) {
> @@ -766,10 +776,7 @@ static int irq_wait_for_interrupt(struct irqaction *action)
> return 0;
> }
> schedule();
> - set_current_state(TASK_INTERRUPTIBLE);
> }
> - __set_current_state(TASK_RUNNING);
> - return -1;
> }
>
> /*
> @@ -990,7 +997,7 @@ static int irq_thread(void *data)
> /*
> * This is the regular exit path. __free_irq() is stopping the
> * thread via kthread_stop() after calling
> - * synchronize_irq(). So neither IRQTF_RUNTHREAD nor the
> + * synchronize_hardirq(). So neither IRQTF_RUNTHREAD nor the
> * oneshot mask bit can be set. We cannot verify that as we
> * cannot touch the oneshot mask at this point anymore as
> * __setup_irq() might have given out currents thread_mask
> @@ -1595,7 +1602,7 @@ static struct irqaction *__free_irq(struct irq_desc *desc, void *dev_id)
> unregister_handler_proc(irq, action);
>
> /* Make sure it's not being used on another CPU: */
> - synchronize_irq(irq);
> + synchronize_hardirq(irq);
So after that, action can be freed and when the thread above tries to
access it. Nice Use After Free. That needs more thought.
Thanks,
tglx
next prev parent reply other threads:[~2018-06-21 20:21 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-24 20:45 [PATCH] genirq: Synchronize only with single thread on free_irq() Lukas Wunner
2018-06-21 20:21 ` Thomas Gleixner [this message]
2018-06-22 8:01 ` Lukas Wunner
2018-06-22 19:44 ` Thomas Gleixner
2018-06-22 20:11 ` Thomas Gleixner
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