[v6,0/2] Restrict xmon when kernel is locked down

Message

Christopher M. Riedl Aug. 30, 2019, 3:37 a.m. UTC

Xmon should be either fully or partially disabled depending on the
kernel lockdown state.

Put xmon into read-only mode for lockdown=integrity and completely
disable xmon when lockdown=confidentiality. Since this can occur
dynamically, there may be pre-existing, active breakpoints in xmon when
transitioning into read-only mode. These breakpoints will still trigger,
so allow them to be listed and cleared using xmon.

Changes since v5:
 - Do not spam print messages when attempting to enter xmon when
   lockdown=confidentiality

Changes since v4:
 - Move lockdown state checks into xmon_core
 - Allow clearing of breakpoints in xmon read-only mode
 - Test simple scenarios (combinations of xmon and lockdown cmdline
   options, setting breakpoints and changing lockdown state, etc) in
   QEMU and on an actual POWER8 VM
 - Rebase onto security/next-lockdown
   b602614a81078bf29c82b2671bb96a63488f68d6

Changes since v3:
 - Allow active breakpoints to be shown/listed in read-only mode

Changes since v2:
 - Rebased onto v36 of https://patchwork.kernel.org/cover/11049461/
   (based on: f632a8170a6b667ee4e3f552087588f0fe13c4bb)
 - Do not clear existing breakpoints when transitioning from
   lockdown=none to lockdown=integrity
 - Remove line continuation and dangling quote (confuses checkpatch.pl)
   from the xmon command help/usage string

Christopher M. Riedl (2):
  powerpc/xmon: Allow listing and clearing breakpoints in read-only mode
  powerpc/xmon: Restrict when kernel is locked down

 arch/powerpc/xmon/xmon.c     | 108 +++++++++++++++++++++++++++--------
 include/linux/security.h     |   2 +
 security/lockdown/lockdown.c |   2 +
 3 files changed, 87 insertions(+), 25 deletions(-)