[RFC PATCH v2 0/2] Fix incorrect overlayfs mmap() and mprotect() LSM access controls

[Paul Moore <paul@paul-moore.com>]

This is a follow-up revision to the patchset[1] posted a week ago.  This
second version has changed significantly in terms of approach and
implementation, as it has become clear that the overlayfs/VFS devs are
unable to make the user O_PATH file approach work.  Unfortunately, this
pushes a lot of the complexity down into the LSM, as opposed to the
backing file code, and will likely result in code and state duplication
across the different LSMs, but at this point in time it doesn't appear
we have any other options.

I'm marking this patchset as a RFC since I've only done basic testing
on this patchset, and I still haven't satisfied myself that the code
covers all of the different cases.  Additional inspection and testing
is required, however, please feel free to take a look and comment on
anything that looks odd.  As always, additional testing is welcome and
encouraged.

[1] https://lore.kernel.org/linux-security-module/20260316213606.374109-5-paul@paul-moore.com/

--
CHANGELOG:
v2:
- remove the user O_PATH file patch from Amir
- add the backing_file LSM blob and lifecycle hooks
- update the SELinux code to reflect the other changes
v1:
- initial version

--
Paul Moore (2):
      lsm: add backing_file LSM hooks
      selinux: fix overlayfs mmap() and mprotect() access checks

 fs/backing-file.c                 |   18 +-
 fs/erofs/ishare.c                 |   10 +
 fs/file_table.c                   |   21 ++
 fs/fuse/passthrough.c             |    2 
 fs/internal.h                     |    3 
 fs/overlayfs/dir.c                |    2 
 fs/overlayfs/file.c               |    2 
 include/linux/backing-file.h      |    4 
 include/linux/fs.h                |    1 
 include/linux/lsm_audit.h         |    2 
 include/linux/lsm_hook_defs.h     |    5 
 include/linux/lsm_hooks.h         |    1 
 include/linux/security.h          |   22 ++
 security/lsm.h                    |    1 
 security/lsm_init.c               |    9 +
 security/security.c               |  100 +++++++++++
 security/selinux/hooks.c          |  252 +++++++++++++++++++++---------
 security/selinux/include/objsec.h |   17 ++
 18 files changed, 387 insertions(+), 85 deletions(-)