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Re: [XEN PATCH v12 4/7] x86/domctl: Add hypercall to set the access of x86 gsi
- To: Roger Pau Monné <roger.pau@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Thu, 1 Aug 2024 15:11:29 +0200
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- Cc: "Daniel P . Smith" <dpsmith@xxxxxxxxxxxxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, George Dunlap <gwd@xxxxxxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Anthony PERARD <anthony@xxxxxxxxxxxxxx>, Juergen Gross <jgross@xxxxxxxx>, Stewart Hildebrand <Stewart.Hildebrand@xxxxxxx>, Huang Rui <ray.huang@xxxxxxx>, Jiqian Chen <Jiqian.Chen@xxxxxxx>
- Delivery-date: Thu, 01 Aug 2024 13:11:39 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 01.08.2024 14:41, Roger Pau Monné wrote:
> On Thu, Aug 01, 2024 at 01:36:16PM +0200, Jan Beulich wrote:
>> On 01.08.2024 13:06, Roger Pau Monné wrote:
>>> On Mon, Jul 08, 2024 at 07:41:21PM +0800, Jiqian Chen wrote:
>>>> Remaining comment @Daniel P . Smith:
>>>> + ret = -EPERM;
>>>> + if ( !irq_access_permitted(currd, irq) ||
>>>> + xsm_irq_permission(XSM_HOOK, d, irq, access_flag) )
>>>> + goto gsi_permission_out;
>>>> Is it okay to issue the XSM check using the translated value,
>>>> not the one that was originally passed into the hypercall?
>>>
>>> FWIW, I don't see the GSI -> IRQ translation much different from the
>>> pIRQ -> IRQ translation done by pirq_access_permitted(), which is also
>>> ahead of the xsm check.
>>
>> The question (which I raised originally) isn't an ordering one, but an
>> auditing one: Is it okay to pass the XSM hook a value that isn't what
>> was passed into the hypercall?
>
> But that's also the case with the current XEN_DOMCTL_irq_permission
> implementation? As the hypercall parameter is a pIRQ, and the XSM
> check is done against the translated IRQ obtained from the pIRQ
> parameter.
In a way you're right, but in a way there's also a meaningful difference:
There we translate between internal numbering spaces. Here we first
translate a quantity in a numbering space superimposed onto us to an
internal representation. Flask, otoh, in such a situation may prefer to
see the external representation of the resource.
Jan
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