[PATCH v2 0/2] vfs/security/NFS/btrfs: clean up and fix LSM option handling

Ondrej Mosnacek omosnace at redhat.com
Mon May 17 13:41:59 UTC 2021

This series fixes two bugs:
1. A bug with BTRFS where LSM options are ignored when BTRFS is mounted
   via the new fsconfig(2) API. (fixed by patch 1)
2. A bug with NFS + SELinux where an attempt to do the same mount twice
   might incidentally turn off LSM labeling, making any fresh inode
   show up as unlabeled. (fixed by patch 2, with patch 1 as a prereq)

For bug (1.) I previously posted a different patch [1], which is no
longer needed if these patches are applied.

While these patches do add a new fs_type flag (which seems to be frowned
upon), they also reduce the semantics of FS_BINARY_MOUNT_DATA flag to
*only* the mount data being binary, while before it was also (ab)used
to skip mount option processing in SELinux for NFS and BTRFS. The result
is perhaps still not perfect, but it seems to be the only non-invasive
solution for these bugs in the short term. Once BTRFS is finally
converted to the new mount API, a lot of the ugliness can likely be
refactored to something nicer (and these patches do not really make that
any harder to do, IMHO).

I tested the patches by running the NFS part of the SELinux testsuite
[2] (which is now fully passing). I also ran the proposed BTRFS SELinux
test coverage for selinux-testsuite [3], which is now passing.

Changes since v1:
- in BTRFS, move the FS_HANDLES_LSM_OPTS flag to btrfs_root_fs_type, and
  remove FS_BINARY_MOUNTDATA from both fs_types now

v1: https://lore.kernel.org/selinux/20210409111254.271800-1-omosnace@redhat.com/T/

[1] https://lore.kernel.org/selinux/20210401065403.GA1363493@infradead.org/T/
[2] https://github.com/SELinuxProject/selinux-testsuite/
[3] https://lore.kernel.org/selinux/20201103110121.53919-2-richard_c_haines@btinternet.com/
    ^^ the original patch no longer applies - a rebased version is here:

Ondrej Mosnacek (2):
  vfs,LSM: introduce the FS_HANDLES_LSM_OPTS flag
  selinux: fix SECURITY_LSM_NATIVE_LABELS flag handling on double mount

 fs/btrfs/super.c         | 34 +++++-----------------------------
 fs/nfs/fs_context.c      |  6 ++++--
 fs/super.c               | 10 ++++++----
 include/linux/fs.h       |  3 ++-
 security/selinux/hooks.c | 32 +++++++++++++++++---------------
 5 files changed, 34 insertions(+), 51 deletions(-)


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