On 07/06/2018 08:28 PM, Xiubo Li wrote:
> On 2018/7/7 2:23, Mike Christie wrote:
>> On 07/05/2018 09:57 PM, xiu...@redhat.com wrote:
>>> static irqreturn_t uio_interrupt(int irq, void *dev_id)
>>> {
>>> struct uio_device *idev = (struct uio_device *)dev_id;
>>> - irqreturn_t ret = idev->info->handler(irq, idev->info);
>>> + irqreturn_t ret;
>>> +
>>> + mutex_lock(&idev->info_lock);
>>> + if (!idev->info) {
>>> + ret = IRQ_NONE;
>>> + goto out;
>>> + }
>>> + ret = idev->info->handler(irq, idev->info);
>>> if (ret == IRQ_HANDLED)
>>> uio_event_notify(idev->info);
>>> +out:
>>> + mutex_unlock(&idev->info_lock);
>>> return ret;
>>> }
>>
>> Do you need the interrupt related changes in this patch and the first
>> one?
> Actually, the NULL checking is not a must, we can remove this. But the
> lock/unlock is needed.
>> When we do uio_unregister_device -> free_irq does free_irq return
>> when there are no longer running interrupt handlers that we requested?
>>
>> If that is not the case then I think we can hit a similar bug. We do:
>>
>> __uio_register_device -> device_register -> device's refcount goes to
>> zero so we do -> uio_device_release -> kfree(idev)
>>
>> and if it is possible the interrupt handler could still run after
>> free_irq then we would end up doing:
>>
>> uio_interrupt -> mutex_lock(&idev->info_lock) -> idev access freed
>> memory.
>
> I think this shouldn't happen. Because the free_irq function does not
> return until any executing interrupts for this IRQ have completed.
>
If free_irq returns after executing interrupts and does not allow new
executions what is the lock protecting in uio_interrupt?
