[PATCH bpf v3 0/2] libbpf: Reject local struct_ops bitfields before data access

[Mingpei CAO <caomingpei@gmail.com>]

A local struct_ops type can contain a bitfield absent from the
corresponding kernel BTF type. libbpf calculated the member data pointer
from the encoded BTF member offset before rejecting the bitfield. The
absent member zero check could then read outside the local struct_ops data
and crash libbpf.

Patch 1 rejects local bitfields before calculating the member data pointer.
Patch 2 adds a negative test for a local bitfield absent from the kernel
BTF type.

AI assistance was used to prepare the messages. I independently reviewed the code and test results.

Changes since v2:
- Restore the local bitfield check from v1.
- Drop general offset validation and the bpftool changes, which covered
  malformed BTF outside.
- Describe the local struct_ops type and absent kernel member.
- Keep the negative test and check the load result before the diagnostic.

v2: https://lore.kernel.org/bpf/20260913145233.1446643-1-caomingpei@gmail.com/
v1: https://lore.kernel.org/bpf/20260910172340.1467764-1-caomingpei@gmail.com/

Mingpei CAO (2):
  libbpf: Reject local struct_ops bitfields before data access
  selftests/bpf: Test local struct_ops bitfield rejection

 tools/lib/bpf/libbpf.c                        |  9 ++++--
 .../bpf/prog_tests/test_struct_ops_module.c   | 32 +++++++++++++++++++
 .../selftests/bpf/progs/struct_ops_module.c   |  7 ++++
 3 files changed, 46 insertions(+), 2 deletions(-)


base-commit: ee363e055895364039bf28348ff13c615afad4ba
-- 
2.43.0