On Tue, Oct 29, 2019 at 12:02:34PM +0100, David Hildenbrand wrote: > 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? 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]. Do you mean that one application creates MAP_EXCLUSIVE and another applications accesses the same physical pages via /dev/mem? With /dev/mem all physical memory is visible... > [1] https://lwn.net/Articles/778240/ > > -- > > Thanks, > > David / dhildenb > -- Sincerely yours, Mike.
