Messages in this thread | | | Date | Thu, 8 Aug 2019 21:56:14 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: [PATCH 1/2] genirq: introduce update_irq_devid() |
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On Thu, 8 Aug 2019, Ben Luo wrote: > +int update_irq_devid(unsigned int irq, void *dev_id, void *new_dev_id) > +{ > + struct irq_desc *desc = irq_to_desc(irq); > + struct irqaction *action, **action_ptr; > + unsigned long flags; > + > + WARN(in_interrupt(), > + "Trying to update IRQ %d from IRQ context!\n", irq);
This is broken. The function needs to return on that condition. Actually it cannot even be called from non-preemptible code.
What's worse is that if the interrupt in question is handled concurrently, then it will either see the old or the new dev_id and because the interrupt handler loop runs with desc->lock dropped even more crap can happen because dev_id can be subject to load and store tearing.
Staring at that, I see that there is the same issue in setup_irq() and free_irq(). It's actually worse there. I'll have a look.
> + /* > + * There can be multiple actions per IRQ descriptor, find the right > + * one based on the dev_id: > + */ > + action_ptr = &desc->action; > + for (;;) { > + action = *action_ptr; > + > + if (!action) { > + WARN(1, "Trying to update already-free IRQ %d\n", irq);
That's wrong in two aspects:
1) The warn should be outside of the locked region.
2) Just having the irq number is not useful for debugging either when the interrupt is shared.
> + raw_spin_unlock_irqrestore(&desc->lock, flags); > + chip_bus_sync_unlock(desc); > + return -ENXIO; > + } > + > + if (action->dev_id == dev_id) { > + action->dev_id = new_dev_id; > + break; > + } > + action_ptr = &action->next; > + } > + > + raw_spin_unlock_irqrestore(&desc->lock, flags); > + chip_bus_sync_unlock(desc); > + > + /* > + * Make sure it's not being used on another CPU: > + * There is a risk of UAF for old *dev_id, if it is > + * freed in a short time after this func returns > + */ > + synchronize_irq(irq); > + > + return 0; > +} > +EXPORT_SYMBOL(update_irq_devid);
EXPORT_SYMBOL_GPL() please.
Thanks,
tglx
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