linux-kernel - Re: [PATCH 15/17] vfio/pci: Let enable and disable of interrupt types use same signature

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Date: Tue, 6 Feb 2024 13:46:37 -0800
From: Reinette Chatre <reinette.chatre@...el.com>
To: Alex Williamson <alex.williamson@...hat.com>
CC: <jgg@...dia.com>, <yishaih@...dia.com>,
	<shameerali.kolothum.thodi@...wei.com>, <kevin.tian@...el.com>,
	<kvm@...r.kernel.org>, <dave.jiang@...el.com>, <ashok.raj@...el.com>,
	<linux-kernel@...r.kernel.org>, <patches@...ts.linux.dev>
Subject: Re: [PATCH 15/17] vfio/pci: Let enable and disable of interrupt types
 use same signature

Hi Alex,

On 2/5/2024 2:35 PM, Alex Williamson wrote:
> On Thu,  1 Feb 2024 20:57:09 -0800
> Reinette Chatre <reinette.chatre@...el.com> wrote:

..

>> @@ -715,13 +724,13 @@ static int vfio_pci_set_intx_trigger(struct vfio_pci_core_device *vdev,
>>  		if (is_intx(vdev))
>>  			return vfio_irq_set_block(vdev, start, count, fds, index);
>>  
>> -		ret = vfio_intx_enable(vdev);
>> +		ret = vfio_intx_enable(vdev, start, count, index);
> 
> Please trace what happens when a user calls SET_IRQS to setup a trigger
> eventfd with start = 0, count = 1, followed by any other combination of
> start and count values once is_intx() is true.  vfio_intx_enable()
> cannot be the only place we bounds check the user, all of the INTx
> callbacks should be an error or nop if vector != 0.  Thanks,
> 

Thank you very much for catching this. I plan to add the vector
check to the device_name() and request_interrupt() callbacks. I do
not think it is necessary to add the vector check to disable() since
it does not operate on a range and from what I can tell it depends on
a successful enable() that already contains the vector check. Similar,
free_interrupt() requires a successful request_interrupt() (that will
have vector check in next version).
send_eventfd() requires a valid interrupt context that is only
possible if enable() or request_interrupt() succeeded.

If user space creates an eventfd with start = 0 and count = 1
and then attempts to trigger the eventfd using another combination then
the changes in this series will result in a nop while the current
implementation will result in -EINVAL. Is this acceptable?

Reinette