[PATCH bpf 2/2] bpf/selftests: test that kernel rejects a TCP CC with an invalid license
From: Toke Høiland-Jørgensen <hidden>
Date: 2021-03-25 15:42:22
Also in:
bpf
Subsystem:
bpf [general] (safe dynamic programs and tools), bpf [selftests] (test runners & infrastructure), kernel selftest framework, the rest · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Shuah Khan, Linus Torvalds
This adds a selftest to check that the verifier rejects a TCP CC struct_ops with a non-GPL license. To save having to add a whole new BPF object just for this, reuse the dctcp CC, but rewrite the license field before loading. Signed-off-by: Toke Høiland-Jørgensen <redacted> --- .../selftests/bpf/prog_tests/bpf_tcp_ca.c | 31 +++++++++++++++++++ 1 file changed, 31 insertions(+)
diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_tcp_ca.c b/tools/testing/selftests/bpf/prog_tests/bpf_tcp_ca.c
index 37c5494a0381..613cf8a00b22 100644
--- a/tools/testing/selftests/bpf/prog_tests/bpf_tcp_ca.c
+++ b/tools/testing/selftests/bpf/prog_tests/bpf_tcp_ca.c@@ -227,10 +227,41 @@ static void test_dctcp(void) bpf_dctcp__destroy(dctcp_skel); } +static void test_invalid_license(void) +{ + /* We want to check that the verifier refuses to load a non-GPL TCP CC. + * Rather than create a whole new file+skeleton, just reuse an existing + * object and rewrite the license in memory after loading. Sine libbpf + * doesn't expose this, we define a struct that includes the first couple + * of internal fields for struct bpf_object so we can overwrite the right + * bits. Yes, this is a bit of a hack, but it makes the test a lot simpler. + */ + struct bpf_object_fragment { + char name[BPF_OBJ_NAME_LEN]; + char license[64]; + } *obj; + struct bpf_dctcp *skel; + int err; + + skel = bpf_dctcp__open(); + if (CHECK(!skel, "bpf_dctcp__open", "failed\n")) + return; + + obj = (void *)skel->obj; + obj->license[0] = 'X'; // turns 'GPL' into 'XPL' which will fail the check + + err = bpf_dctcp__load(skel); + CHECK(err != -LIBBPF_ERRNO__VERIFY, "bpf_dctcp__load", "err:%d\n", err); + + bpf_dctcp__destroy(skel); +} + void test_bpf_tcp_ca(void) { if (test__start_subtest("dctcp")) test_dctcp(); if (test__start_subtest("cubic")) test_cubic(); + if (test__start_subtest("invalid_license")) + test_invalid_license(); }
--
2.31.0