[bpf,v2,0/2] bpf: fix NULL dereference during extable search

Message

Krister Johansen June 7, 2023, 9:04 p.m. UTC

Hi,
Enclosed are a pair of patches for an oops that can occur if an exception is
generated while a bpf subprogram is running.  One of the bpf_prog_aux entries
for the subprograms are missing an extable.  This can lead to an exception that
would otherwise be handled turning into a NULL pointer bug.

The bulk of the change here is simply adding a pair of programs for the
selftest.  The proposed fix in this iteration is a 1-line change.

These changes were tested via the verifier and progs selftests and no
regressions were observed.

Changes from v1:

- Add a selftest (Feedback From Alexei Starovoitov)
- Move to a 1-line verifier change instead of searching multiple extables

Krister Johansen (2):
  Add a selftest for subprogram extables
  bpf: ensure main program has an extable

 kernel/bpf/verifier.c                         |  1 +
 .../bpf/prog_tests/subprogs_extable.c         | 35 +++++++++
 .../bpf/progs/test_subprogs_extable.c         | 71 +++++++++++++++++++
 3 files changed, 107 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/subprogs_extable.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_subprogs_extable.c