[PATCH -next 0/9] lockdown: fix the securityfs interface and add tests

[Cai Xinchen <caixinchen1@huawei.com>]

The lockdown LSM exposes /sys/kernel/security/lockdown, but the file is
not documented and has no selftest.  While looking at the interface we
also found a configuration bug and several accumulated cleanups.

The series is organized as follows:

  - patches 1-2 are small cleanups in lockdown_write(): stop scanning
    after the matching level and drop an update to a length variable
    that is not used afterwards.
  - patch 3 replaces sprintf() with scnprintf() so that the status
    buffer is bounded explicitly if more levels are added later.
  - patch 4 makes the LSM select SECURITYFS.  Without it, a kernel
    built with CONFIG_SECURITYFS=n logs "failed LSM lockdown core
    initcall with errno -19" and does not create the file advertised
    by the Kconfig help text.
  - patch 5 removes LSM_AUDIT_DATA_LOCKDOWN and its formatting code,
    which became dead when the SELinux lockdown implementation was
    removed by commit f5d0e5e9d72d.
  - patches 6-7 drop an unused include, simplify the securityfs
    registration, and move lockdown_reasons[] next to its only user.
  - patch 8 documents the ABI and adds the new file to the LOCKDOWN
    SECURITY MODULE entry in MAINTAINERS.
  - patch 9 adds a kselftest covering the read format, invalid levels,
    and the rejection of the current or a lower level.

The only functional change is patch 4; the rest are cleanups,
documentation, or test coverage.  The selftest never escalates
lockdown on the machine where it runs.

Cai Xinchen (8):
  lockdown: Add break in lockdown_write
  lockdown: bound the status string with scnprintf
  lockdown: select SECURITYFS
  lsm: remove unused lockdown audit data
  lockdown: drop an unused include and simplify secfs init
  lockdown: move lockdown_reasons next to its only user
  Documentation/ABI: document the lockdown securityfs file
  selftests/lsm: add lockdown securityfs test

Kalevi Kolttonen (1):
  lockdown: remove useless decrement operation

 Documentation/ABI/testing/securityfs-lockdown |  41 ++++
 MAINTAINERS                                   |   1 +
 include/linux/lsm_audit.h                     |   2 -
 include/linux/security.h                      |   2 -
 security/lockdown/Kconfig                     |   1 +
 security/lockdown/lockdown.c                  |  63 +++++--
 security/lsm_audit.c                          |   4 -
 security/security.c                           |  40 ----
 tools/testing/selftests/lsm/Makefile          |   3 +-
 tools/testing/selftests/lsm/common.c          |  35 +++-
 tools/testing/selftests/lsm/common.h          |   2 +
 tools/testing/selftests/lsm/lockdown_test.c   | 176 ++++++++++++++++++
 12 files changed, 300 insertions(+), 70 deletions(-)
 create mode 100644 Documentation/ABI/testing/securityfs-lockdown
 create mode 100644 tools/testing/selftests/lsm/lockdown_test.c

-- 
2.18.0.huawei.25