linux-kernel - [PATCH bpf v2 0/2] bpf: fix NULL dereference during extable search

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Message-ID: <cover.1686166633.git.kjlx@templeofstupid.com>
Date:   Wed, 7 Jun 2023 14:04:16 -0700
From:   Krister Johansen <kjlx@...pleofstupid.com>
To:     bpf@...r.kernel.org
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <martin.lau@...ux.dev>,
        Song Liu <song@...nel.org>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Stanislav Fomichev <sdf@...gle.com>,
        Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
        Mykola Lysenko <mykolal@...com>, Shuah Khan <shuah@...nel.org>,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
        stable@...r.kernel.org
Subject: [PATCH bpf v2 0/2] bpf: fix NULL dereference during extable search

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

-- 
2.25.1