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SubjectRe: [PATCH 1/2] genirq: introduce update_irq_devid()
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在 2019/8/9 上午3:56, Thomas Gleixner 写道:
> 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.

ok,  will return with an error code in v2 in this case

>
>> + /*
>> + * 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.
will take care in v2
>> + 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, will use EXPORT_SYMBOL_GPL in v2
>
> Thanks,
>
> tglx

Thanks,

     Ben

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