Re: [PATCH v7 6/6] mm/memfd: security hook for memfd_create

[Jeff Xu]

On Fri, Dec 9, 2022 at 10:29 AM Paul Moore <paul@xxxxxxxxxxxxxx> wrote:
>
> On Fri, Dec 9, 2022 at 11:05 AM <jeffxu@xxxxxxxxxxxx> wrote:
> >
> > From: Jeff Xu <jeffxu@xxxxxxxxxx>
> >
> > The new security_memfd_create allows lsm to check flags of
> > memfd_create.
> >
> > The security by default system (such as chromeos) can use this
> > to implement system wide lsm to allow only non-executable memfd
> > being created.
> >
> > Signed-off-by: Jeff Xu <jeffxu@xxxxxxxxxx>
> > Reported-by: kernel test robot <lkp@xxxxxxxxx>
> > ---
> >  include/linux/lsm_hook_defs.h | 1 +
> >  include/linux/lsm_hooks.h     | 4 ++++
> >  include/linux/security.h      | 6 ++++++
> >  mm/memfd.c                    | 5 +++++
> >  security/security.c           | 5 +++++
> >  5 files changed, 21 insertions(+)
>
> We typically require at least one in-tree LSM implementation to
> accompany a new LSM hook.  Beyond simply providing proof that the hook
> has value, it helps provide a functional example both for reviewers as
> well as future LSM implementations.  Also, while the BPF LSM is
> definitely "in-tree", its nature is such that the actual
> implementation lives out-of-tree; something like SELinux, AppArmor,
> Smack, etc. are much more desirable from an in-tree example
> perspective.
>
Thanks for the comments.
Would that be OK if I add a new LSM in the kernel  to block executable
memfd creation ?
Alternatively,  it might be possible to add this into SELinux or
landlock, it will be a larger change.

Thanks

Jeff


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