Re: [PATCH RFC] mm: add MAP_EXCLUSIVE to create exclusive user mappings

David Hildenbrand
2019-10-29T11:02:47Z

On 27.10.19 11:17, Mike Rapoport wrote:
> From: Mike Rapoport <rppt@linux.ibm.com>
>
> The mappings created with MAP_EXCLUSIVE are visible only in the context of
> the owning process and can be used by applications to store secret
> information that will not be visible not only to other processes but to the
> kernel as well.
>
> The pages in these mappings are removed from the kernel direct map and
> marked with PG_user_exclusive flag. When the exclusive area is unmapped,
> the pages are mapped back into the direct map.
>

Just a thought, the kernel is still able to indirectly read the contents
of these pages by doing a kdump from kexec environment, right?. Also, I
wonder what would happen if you map such pages via /dev/mem into another
user space application and e.g., use them along with kvm [1].

[1] https://lwn.net/Articles/778240/

--

Thanks,

David / dhildenb