Re: [Xen-devel] [PATCH v7 10/10] xen/common: do not implicitly permit access to mapped I/O memory

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 25.05.14 at 19:14, <julien.grall@xxxxxxxxxx> wrote:
> On 06/05/14 10:06, Jan Beulich wrote:
>>> @@ -838,7 +842,7 @@ long do_domctl(XEN_GUEST_HANDLE_PARAM(xen_domctl_t) 
>>> u_domctl)
>>>               break;
>>>
>>>           ret = -EPERM;
>>> -        if ( !iomem_access_permitted(current->domain, mfn, mfn_end) )
>>> +        if ( !iomem_access_permitted(d, mfn, mfn_end) )
>>
>> I'm not sure if we shouldn't rather be conservative here and check
>> both domains' permissions.
> 
> I think we only need to check the permission of the current domain. 
> Checking the permission of the guest is not necessary here. Hence, the 
> code to map a region will be more difficult. We will have first call 
> iomem_permission then call memory_mapping.
> 
> I would prefer to keep the current permission check ie:
> 
> if ( !iomem_access_permitted(current->domain, ...) )

In fact my earlier comment was wrong - for some reason I was
thinking this was the mapping operation that gets modified here,
not the permission one. For the permission one it is of course
wrong to check the subject domain's permissions, as they're only
about to be granted.

Jan


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel