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

From: David Hildenbrand
Date: Tue Oct 29 2019 - 07:02:47 EST

On 27.10.19 11:17, Mike Rapoport wrote:
From: Mike Rapoport <rppt@xxxxxxxxxxxxx>

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].




David / dhildenb