Re: [PATCH 10/17] prmem: documentation

From: Igor Stoppa
Date: Tue Nov 13 2018 - 13:33:51 EST


I forgot one sentence :-(

On 13/11/2018 20:31, Igor Stoppa wrote:
> On 13/11/2018 19:47, Andy Lutomirski wrote:
>
>> For general rare-writish stuff, I don't think we want IRQs running
>> with them mapped anywhere for write. For AVC and IMA, I'm less sure.
>
> Why would these be less sensitive?
>
> But I see a big difference between my initial implementation and this one.
>
> In my case, by using a shared mapping, visible to all cores, freezing
> the core that is performing the write would have exposed the writable
> mapping to a potential attack run from another core.
>
> If the mapping is private to the core performing the write, even if it
> is frozen, it's much harder to figure out what it had mapped and where,
> from another core.
>
> To access that mapping, the attack should be performed from the ISR, I
> think.

Unless the secondary mapping is also available to other cores, through
the shared mm_struct ?

--
igor