Paul Moore writes: > On Tue, Dec 13, 2022 at 10:00 AM Jeff Xu wrote: >> On Fri, Dec 9, 2022 at 10:29 AM Paul Moore wrote: >> > On Fri, Dec 9, 2022 at 11:05 AM wrote: >> > > >> > > From: Jeff Xu >> > > >> > > 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 >> > > Reported-by: kernel test robot >> > > — >> > > 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 ? > > If you would be proposing the LSM only to meet the requirement of > providing an in-tree LSM example, no that would definitely *not* be > okay. > > Proposing a new LSM involves documenting a meaningful security model, > implementing it, developing tests, going through a (likely multi-step) > review process, and finally accepting the long term maintenance > responsibilities of this new LSM. If you are proposing a new LSM > because you feel the current LSMs do not provide a security model > which meets your needs, then yes, proposing a new LSM might be a good > idea. However, if you are proposing a new LSM because you don’t want > to learn how to add a new hook to an existing LSM, then I suspect you > are misguided/misinformed with the amount of work involved in > submitting a new LSM. > >> Alternatively, it might be possible to add this into SELinux or >> landlock, it will be a larger change. > > It will be a much smaller change than submitting a new LSM, and it > would have infinitely more value to the community than a throw-away > LSM where the only use-case is getting your code merged upstream. Hi Paul/everyone! I am not sure what is the latest here. But it seems both landlock[1] and IPE[2] have a use case for memfd_create(2) LSM hook. I would be happy to work on the use case for such a hook for landlock. CC’ing maintainers for both LSMs. -Abhinav [1] - [2] -