[bpf,0/4] Fix caching of BTF for kfuncs in the verifier

Message

Toke Høiland-Jørgensen Oct. 8, 2024, 10:35 a.m. UTC

When playing around with defining kfuncs in some custom modules, we
noticed that if a BPF program calls two functions with the same
signature in two different modules, the function from the wrong module
may sometimes end up being called. Whether this happens depends on the
order of the calls in the BPF program, which turns out to be due to the
use of sort() inside __find_kfunc_desc_btf() in the verifier code.

This series contains a fix for the issue (first patch), and a selftest
to trigger it (last patch). The two middle commits refactor some of the
selftest code to better handle building and loading multiple kernel
modules as part of the testing. See the individual patch descriptions
for more details.

---
Simon Sundberg (2):
      selftests/bpf: Provide a generic [un]load_module helper
      selftests/bpf: Add test for kfunc module order

Toke Høiland-Jørgensen (2):
      bpf: fix kfunc btf caching for modules
      selftests/bpf: Consolidate kernel modules into common directory

 kernel/bpf/verifier.c                              |  8 +++-
 tools/testing/selftests/bpf/Makefile               | 35 +++++++-------
 .../testing/selftests/bpf/bpf_test_no_cfi/Makefile | 19 --------
 tools/testing/selftests/bpf/bpf_testmod/Makefile   | 20 --------
 .../testing/selftests/bpf/prog_tests/core_reloc.c  |  2 +-
 .../selftests/bpf/prog_tests/kfunc_module_order.c  | 55 ++++++++++++++++++++++
 tools/testing/selftests/bpf/progs/bad_struct_ops.c |  2 +-
 tools/testing/selftests/bpf/progs/cb_refs.c        |  2 +-
 tools/testing/selftests/bpf/progs/epilogue_exit.c  |  4 +-
 .../selftests/bpf/progs/epilogue_tailcall.c        |  4 +-
 tools/testing/selftests/bpf/progs/iters_testmod.c  |  2 +-
 tools/testing/selftests/bpf/progs/jit_probe_mem.c  |  2 +-
 .../selftests/bpf/progs/kfunc_call_destructive.c   |  2 +-
 .../testing/selftests/bpf/progs/kfunc_call_fail.c  |  2 +-
 .../testing/selftests/bpf/progs/kfunc_call_race.c  |  2 +-
 .../testing/selftests/bpf/progs/kfunc_call_test.c  |  2 +-
 .../selftests/bpf/progs/kfunc_call_test_subprog.c  |  2 +-
 .../selftests/bpf/progs/kfunc_module_order.c       | 30 ++++++++++++
 .../testing/selftests/bpf/progs/local_kptr_stash.c |  2 +-
 tools/testing/selftests/bpf/progs/map_kptr.c       |  2 +-
 tools/testing/selftests/bpf/progs/map_kptr_fail.c  |  2 +-
 tools/testing/selftests/bpf/progs/missed_kprobe.c  |  2 +-
 .../selftests/bpf/progs/missed_kprobe_recursion.c  |  2 +-
 tools/testing/selftests/bpf/progs/nested_acquire.c |  2 +-
 tools/testing/selftests/bpf/progs/pro_epilogue.c   |  4 +-
 .../selftests/bpf/progs/pro_epilogue_goto_start.c  |  4 +-
 tools/testing/selftests/bpf/progs/sock_addr_kern.c |  2 +-
 .../selftests/bpf/progs/struct_ops_detach.c        |  2 +-
 .../selftests/bpf/progs/struct_ops_forgotten_cb.c  |  2 +-
 .../selftests/bpf/progs/struct_ops_maybe_null.c    |  2 +-
 .../bpf/progs/struct_ops_maybe_null_fail.c         |  2 +-
 .../selftests/bpf/progs/struct_ops_module.c        |  2 +-
 .../selftests/bpf/progs/struct_ops_multi_pages.c   |  2 +-
 .../selftests/bpf/progs/struct_ops_nulled_out_cb.c |  2 +-
 .../bpf/progs/test_kfunc_param_nullable.c          |  2 +-
 .../selftests/bpf/progs/test_module_attach.c       |  2 +-
 .../selftests/bpf/progs/test_tp_btf_nullable.c     |  2 +-
 .../testing/selftests/bpf/progs/unsupported_ops.c  |  2 +-
 tools/testing/selftests/bpf/progs/wq.c             |  2 +-
 tools/testing/selftests/bpf/progs/wq_failures.c    |  2 +-
 .../bpf/{bpf_testmod => test_kmods}/.gitignore     |  0
 tools/testing/selftests/bpf/test_kmods/Makefile    | 26 ++++++++++
 .../selftests/bpf/test_kmods/bpf_test_modorder_x.c | 39 +++++++++++++++
 .../selftests/bpf/test_kmods/bpf_test_modorder_y.c | 39 +++++++++++++++
 .../bpf_test_no_cfi.c                              |  0
 .../bpf_testmod-events.h                           |  0
 .../bpf/{bpf_testmod => test_kmods}/bpf_testmod.c  |  0
 .../bpf/{bpf_testmod => test_kmods}/bpf_testmod.h  |  0
 .../bpf_testmod_kfunc.h                            |  0
 tools/testing/selftests/bpf/testing_helpers.c      | 34 ++++++++-----
 tools/testing/selftests/bpf/testing_helpers.h      |  2 +
 51 files changed, 275 insertions(+), 108 deletions(-)
---
base-commit: bcd28cfd04ebd3f871443e4746e511147686e517
change-id: 20241008-fix-kfunc-btf-caching-for-modules-b62603484ffb

Best regards,