Re: [Xen-devel] [PATCH v02 6/7] arm: introduce do_translate_pagetable hypercall

[Andrii Tseglytskyi <andrii.tseglytskyi@xxxxxxxxxxxxxxx>]

Hi Julien,


On Tue, Jul 22, 2014 at 7:44 PM, Julien Grall <julien.grall@xxxxxxxxxx> wrote:
> On 07/22/2014 05:39 PM, Andrii Tseglytskyi wrote:
>> Hi Julien,
>
> Hi Andrii,
>
>> On Fri, Jul 4, 2014 at 5:35 PM, Julien Grall <julien.grall@xxxxxxxxxx> wrote:
>>> Hi Andrii,
>>>
>>>
>>> On 26/06/14 12:07, Andrii Tseglytskyi wrote:
>>>>
>>>> +long do_translate_pagetable(int cmd,
>>>> XEN_GUEST_HANDLE_PARAM(xen_pagetable_addr_t) pgt_addr)
>>>> +{
>>>> +    struct xen_pagetable_addr pgt;
>>>> +    struct mmu_info *mmu = NULL;
>>>> +
>>>> +    if ( copy_from_guest(&pgt, pgt_addr, 1) )
>>>> +        return -EFAULT;
>>>> +
>>>> +    mmu = mmu_lookup(pgt.reg);
>>>> +    if ( !mmu )
>>>> +    {
>>>> +        pr_mmu("can't get mmu for addr 0x%08x", pgt.reg);
>>>> +        return -EINVAL;
>>>> +    }
>>>> +
>>>> +    pgt.maddr = mmu_translate_pagetable(mmu, pgt.paddr);
>>>> +
>>>> +    return copy_to_guest(pgt_addr, &pgt, 1);
>>>> +}
>>>> +
>>>
>>>
>>> AFAIU, nothing prevents a malicious guest to call this hypercall and screw
>>> the pagetable of the MMU.
>>
>> Right. Do you think that some kind of security checks needed here?
>
> You need at least ot check that the domain is allowed to access to the
> remote processor.
>
> It may be implemented via the solution we were talking on patch #1.
>

Agree.


> Regards,
>
> --
> Julien Grall



-- 

Andrii Tseglytskyi | Embedded Dev
GlobalLogic
www.globallogic.com

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