[RFC PATCH for 5.4 0/7] Membarrier fixes and cleanups

[Mathieu Desnoyers]

Hi,

Those series of fixes and cleanups are initially motivated by the report
of race in membarrier, which can load p->mm->membarrier_state after mm
has been freed (use-after-free).

Thanks,

Mathieu

Mathieu Desnoyers (7):
  Fix: sched/membarrier: Private expedited registration check
  Cleanup: sched/membarrier: Remove redundant check
  Cleanup: sched/membarrier: Only sync_core before usermode for same mm
  Fix: sched/membarrier: p->mm->membarrier_state racy load (v4)
  selftests: sched/membarrier: Add multi-threaded test
  sched/membarrier: Skip IPIs when mm->mm_users == 1
  sched/membarrier: Return -ENOMEM to userspace on memory allocation
    failure

 fs/exec.c                                     |   2 +-
 include/linux/mm_types.h                      |  14 +-
 include/linux/sched/mm.h                      |  10 +-
 kernel/sched/core.c                           |   4 +-
 kernel/sched/membarrier.c                     | 236 +++++++++++-------
 kernel/sched/sched.h                          |  34 +++
 tools/testing/selftests/membarrier/.gitignore |   3 +-
 tools/testing/selftests/membarrier/Makefile   |   5 +-
 ...mbarrier_test.c => membarrier_test_impl.h} |  40 +--
 .../membarrier/membarrier_test_multi_thread.c |  73 ++++++
 .../membarrier_test_single_thread.c           |  24 ++
 11 files changed, 329 insertions(+), 116 deletions(-)
 rename tools/testing/selftests/membarrier/{membarrier_test.c => membarrier_test_impl.h} (95%)
 create mode 100644 tools/testing/selftests/membarrier/membarrier_test_multi_thread.c
 create mode 100644 tools/testing/selftests/membarrier/membarrier_test_single_thread.c

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2.17.1