Re: [Xen-devel] [PATCH v3 2/7] xsm: flask: change the dummy xsm policy and flask hook for map_gmfn_foregin

[Zhongze Liu <blackskygg@xxxxxxxxx>]

Hi Jan,

2017-10-23 15:26 GMT+08:00 Jan Beulich <JBeulich@xxxxxxxx>:
>>>> On 22.10.17 at 13:21, <blackskygg@xxxxxxxxx> wrote:
>> How about changing the policy to (c over d) && ((d over t) || (c over t))?
>> Given that (c over d) is a must, which is always checked somewhere higher
>> in the call stack as Daniel pointed out,  permitting (d over t) or (c
>> over t) actually infers
>> permitting the other.
>>
>> - if you permit (d over t) but not (c over t):
>>   Given (c over t),
>>   (c) can first map the src page from (t) into its own memory space and then 
>> map
>>   this page from its own memory space to (d)'s memory space.
>
> Would that work? The page, when in (c)'s space, is still owned by (t),
> so I don't see how mapping into (d)'s space could become possible
> just because it's mapped into (c)'s.

Yes, indeed. This won't work. Sorry for giving a wrong example here.

I think I now agree to add a new subop, too.

Cheers,

Zhongze Liu

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