[bpf-next,00/11] bpf: probe-read bpf_d_path() and add new acquire/release BPF kfuncs

Message

Matt Bobrowski Feb. 20, 2024, 9:27 a.m. UTC

On a number of occasions [0, 1, 2], usage of the pre-existing BPF
helper bpf_d_path() under certain circumstances has led to memory
corruption issues.

This patch series intends to address bpf_d_path()'s susceptibility to
such memory corruption issues by fundamentally swapping out the
underlying bpf_d_path() implementation such that it makes use of
probe-read semantics. Enforcing probe-read semantics onto bpf_d_path()
however doesn't come without it's own set of limitations. Therefore,
to overcome such limitations, this patch series also adds new BPF
kfunc based infrastructure which ultimately allows BPF program authors
to adopt a safer and true implementation of d_path() moving forward
which is fundamentally backed by KF_TRUSTED_ARGS semantics.

[0] https://lore.kernel.org/bpf/CAG48ez0ppjcT=QxU-jtCUfb5xQb3mLr=[e-mail]/
[1] https://lore.kernel.org/bpf/[e-mail]/
[2] https://lore.kernel.org/bpf/[e-mail]/

Matt Bobrowski (11):
  bpf: make bpf_d_path() helper use probe-read semantics
  bpf/selftests: adjust selftests for BPF helper bpf_d_path()
  bpf: rename fs_kfunc_set_ids to lsm_kfunc_set_ids
  bpf: add new acquire/release BPF kfuncs for mm_struct
  bpf/selftests: add selftests for mm_struct acquire/release BPF kfuncs
  bpf: add new acquire/release based BPF kfuncs for exe_file
  bpf/selftests: add selftests for exe_file acquire/release BPF kfuncs
  bpf: add acquire/release based BPF kfuncs for fs_struct's paths
  bpf/selftests: add selftests for root/pwd path based BPF kfuncs
  bpf: add trusted d_path() based BPF kfunc bpf_path_d_path()
  bpf/selftests: adapt selftests test_d_path for BPF kfunc
    bpf_path_d_path()

 fs/Makefile                                   |   6 +-
 fs/probe_read_d_path.c                        | 150 +++++++++++
 include/linux/probe_read_d_path.h             |  13 +
 kernel/trace/bpf_trace.c                      | 249 ++++++++++++++++--
 .../testing/selftests/bpf/prog_tests/d_path.c | 182 +++++++++++--
 .../selftests/bpf/prog_tests/exe_file_kfunc.c |  49 ++++
 .../selftests/bpf/prog_tests/mm_kfunc.c       |  48 ++++
 .../selftests/bpf/prog_tests/path_kfunc.c     |  48 ++++
 .../selftests/bpf/progs/d_path_common.h       |  34 +++
 .../bpf/progs/d_path_kfunc_failure.c          |  66 +++++
 .../bpf/progs/d_path_kfunc_success.c          |  25 ++
 .../bpf/progs/exe_file_kfunc_common.h         |  23 ++
 .../bpf/progs/exe_file_kfunc_failure.c        | 181 +++++++++++++
 .../bpf/progs/exe_file_kfunc_success.c        |  52 ++++
 .../selftests/bpf/progs/mm_kfunc_common.h     |  19 ++
 .../selftests/bpf/progs/mm_kfunc_failure.c    | 103 ++++++++
 .../selftests/bpf/progs/mm_kfunc_success.c    |  30 +++
 .../selftests/bpf/progs/path_kfunc_common.h   |  20 ++
 .../selftests/bpf/progs/path_kfunc_failure.c  | 114 ++++++++
 .../selftests/bpf/progs/path_kfunc_success.c  |  30 +++
 .../testing/selftests/bpf/progs/test_d_path.c |  20 +-
 .../bpf/progs/test_d_path_check_rdonly_mem.c  |   6 +-
 .../bpf/progs/test_d_path_check_types.c       |   6 +-
 23 files changed, 1396 insertions(+), 78 deletions(-)
 create mode 100644 fs/probe_read_d_path.c
 create mode 100644 include/linux/probe_read_d_path.h
 create mode 100644 tools/testing/selftests/bpf/prog_tests/exe_file_kfunc.c
 create mode 100644 tools/testing/selftests/bpf/prog_tests/mm_kfunc.c
 create mode 100644 tools/testing/selftests/bpf/prog_tests/path_kfunc.c
 create mode 100644 tools/testing/selftests/bpf/progs/d_path_common.h
 create mode 100644 tools/testing/selftests/bpf/progs/d_path_kfunc_failure.c
 create mode 100644 tools/testing/selftests/bpf/progs/d_path_kfunc_success.c
 create mode 100644 tools/testing/selftests/bpf/progs/exe_file_kfunc_common.h
 create mode 100644 tools/testing/selftests/bpf/progs/exe_file_kfunc_failure.c
 create mode 100644 tools/testing/selftests/bpf/progs/exe_file_kfunc_success.c
 create mode 100644 tools/testing/selftests/bpf/progs/mm_kfunc_common.h
 create mode 100644 tools/testing/selftests/bpf/progs/mm_kfunc_failure.c
 create mode 100644 tools/testing/selftests/bpf/progs/mm_kfunc_success.c
 create mode 100644 tools/testing/selftests/bpf/progs/path_kfunc_common.h
 create mode 100644 tools/testing/selftests/bpf/progs/path_kfunc_failure.c
 create mode 100644 tools/testing/selftests/bpf/progs/path_kfunc_success.c