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

[Julien Grall <julien.grall@xxxxxxxxxx>]

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.

Regards,

-- 
Julien Grall

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