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SubjectRe: [PATCH v6 0/6] mm: introduce memfd_secret system call to create "secret" memory areas
On Thu, Sep 24, 2020 at 07:34:28PM -0700, Andrew Morton wrote:
> On Thu, 24 Sep 2020 16:28:58 +0300 Mike Rapoport <rppt@kernel.org> wrote:
>
> > From: Mike Rapoport <rppt@linux.ibm.com>
> >
> > Hi,
> >
> > This is an implementation of "secret" mappings backed by a file descriptor.
> > I've dropped the boot time reservation patch for now as it is not strictly
> > required for the basic usage and can be easily added later either with or
> > without CMA.
> >
> > ...
> >
> > The file descriptor backing secret memory mappings is created using a
> > dedicated memfd_secret system call The desired protection mode for the
> > memory is configured using flags parameter of the system call. The mmap()
> > of the file descriptor created with memfd_secret() will create a "secret"
> > memory mapping. The pages in that mapping will be marked as not present in
> > the direct map and will have desired protection bits set in the user page
> > table. For instance, current implementation allows uncached mappings.
> >
> > Although normally Linux userspace mappings are protected from other users,
> > such secret mappings are useful for environments where a hostile tenant is
> > trying to trick the kernel into giving them access to other tenants
> > mappings.
> >
> > Additionally, the secret mappings may be used as a mean to protect guest
> > memory in a virtual machine host.
> >
> > For demonstration of secret memory usage we've created a userspace library
> > [1] that does two things: the first is act as a preloader for openssl to
>
> I can find no [1].

Oops, sorry. It's

https://git.kernel.org/pub/scm/linux/kernel/git/jejb/secret-memory-preloader.git/

> I'm not a fan of the enumerated footnote thing. Why not inline the url
> right here so readers don't need to jump around?
>
>

--
Sincerely yours,
Mike.

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