Re: [PATCH bpf-next 6/7] selftests/bpf: Add tests for the generic netlink BPF hook
From: bot+bpf-ci@kernel.org
Date: 2026-08-31 12:07:12
Also in:
bpf, linux-security-module
Add a few tests for the new generic netlink BPF hook. Policies only apply themselves to the "nlctrl" family. The following tests are being added: * doit: allow or deny CTRL_CMD_GETFAMILY * dump: allow or deny CTRL_CMD_GETPOLICY, nlmsg_flags |= NLM_F_DUMP * nlmsg_flags: allow or deny a command based on nlmsg_flags * other_family: check that other families still pass
The enumeration lists four subtests but the patch registers five. The
"netns" subtest is missing from this list:
if (test__start_subtest("doit")) test_doit(skel, fd);
if (test__start_subtest("dump")) test_dump(skel, fd);
if (test__start_subtest("nlmsg_flags")) test_nlmsg_flags(skel, fd);
if (test__start_subtest("other_family")) test_other_family(skel, fd, other_id);
if (test__start_subtest("netns")) test_netns(skel, fd);
The netns subtest is the only one exercising the net argument of
bpf_lsm_genl_family_rcv_msg(), and it introduces target_netns_inum plus
a filter in the BPF program, netns_new()/open_netns(), a second socket,
and the netns_inum() helper - roughly 45 of the 242 added lines. Since
the netns filtering path is the least obvious part of the hook contract,
would it make sense to add a fifth bullet, for example "* netns: deny a
command only inside a target netns, allow it elsewhere"?
quoted hunk ↗ jump to hunk
diff --git a/tools/testing/selftests/bpf/config b/tools/testing/selftests/bpf/config index 08c6e8a4e..6ca0b083a 100644 --- a/tools/testing/selftests/bpf/config +++ b/tools/testing/selftests/bpf/config@@ -30,6 +30,7 @@ CONFIG_DYNAMIC_FTRACE=y CONFIG_FPROBE=y CONFIG_FUNCTION_TRACER=y
[ ... ]
quoted hunk ↗ jump to hunk
diff --git a/tools/testing/selftests/bpf/prog_tests/genl_lsm.c b/tools/testing/selftests/bpf/prog_tests/genl_lsm.c new file mode 100644 index 000000000..9f866c4c6 --- /dev/null +++ b/tools/testing/selftests/bpf/prog_tests/genl_lsm.c
[ ... ]
+static void test_nlmsg_flags(struct genl_lsm *skel, int fd)
+{
+ int err;
+
+ /* ensure denying works */
+ skel->bss->target_cmd = CTRL_CMD_GETFAMILY;
+ skel->bss->target_flags = NLM_F_REQUEST | NLM_F_DUMP;
+ skel->bss->allow = false;
+
+ err = nlctrl_request(fd, CTRL_CMD_GETFAMILY, false);
+ ASSERT_OK(err, "doit_flags_not_matched");
+
+ err = nlctrl_request(fd, CTRL_CMD_GETFAMILY, true);
+ ASSERT_EQ(err, -TEST_ERRNO, "deny_dump_flags");
+
+ /* now, the other way around */
+ skel->bss->target_flags = NLM_F_REQUEST;
+
+ err = nlctrl_request(fd, CTRL_CMD_GETFAMILY, true);
+ ASSERT_OK(err, "doit_flags_not_matched");
+
+ err = nlctrl_request(fd, CTRL_CMD_GETFAMILY, false);
+ ASSERT_EQ(err, -TEST_ERRNO, "deny_dump_flags");
+}The second half reuses the assertion tags from the first half, but they name the opposite case. The dump request gets "doit_flags_not_matched" and the doit request gets "deny_dump_flags". The test logic is correct but when test_progs prints only the tag and __func__, a CI failure reporting "genl_lsm:FAIL:deny_dump_flags" cannot be attributed to either of the two assertions with that name, and whichever one it is, the tag names the wrong netlink operation. Would four distinct tags - for example "deny_dump_flags_matched", "allow_doit_flags_unmatched", "allow_dump_flags_unmatched", "deny_doit_flags_matched" - remove the ambiguity? [ ... ]
+void test_genl_lsm(void)
+{
+ struct genl_lsm *skel = NULL;
+ int fd = -1;
+ int err, other_id;
+
+ skel = genl_lsm__open_and_load();
+ if (!ASSERT_OK_PTR(skel, "genl_lsm__open_and_load"))
+ return;
+
+ fd = genl_open(0);
+ if (!ASSERT_OK_FD(fd, "genl_open"))
+ goto cleanup;
+
+ /* do this before attaching our hook, just in case */
+ other_id = genl_resolve_family(fd, OTHER_FAMILY_NAME);
+ if (other_id == -ENOENT) {
+ test__skip();
+ goto cleanup;
+ }A subsystem pattern flags this as potentially concerning: when CONFIG_ETHTOOL_NETLINK is absent, genl_resolve_family() returns -ENOENT and the test skips with no printed reason. A reader of the TAP output sees "#N genl_lsm:SKIP" with nothing indicating the missing prerequisite was the ethtool genl family, so a silently-skipped test looks identical to a deliberately-disabled one. All five subtests are skipped this way, including the four (doit, dump, nlmsg_flags, netns) that do not need ethtool - only test_other_family() consumes other_id. This pattern is common in bpf selftests (e.g. aggregate_ret.c:52, arena_spin_lock.c:57 and :66 all do exactly this), and the config hunk in this same patch adds CONFIG_ETHTOOL_NETLINK so the skip path should not be taken in a properly configured CI run. Would a one-line printf plus optionally deferring the ethtool resolution into test_other_family() so the other four subtests still run be worth addressing? [ ... ]
quoted hunk ↗ jump to hunk
diff --git a/tools/testing/selftests/bpf/progs/genl_lsm.c b/tools/testing/selftests/bpf/progs/genl_lsm.c new file mode 100644 index 000000000..c4d8b4d23 --- /dev/null +++ b/tools/testing/selftests/bpf/progs/genl_lsm.c
[ ... ] --- AI reviewed your patch. Please fix the bug or email reply why it's not a bug. See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md CI run summary: https://github.com/kernel-patches/bpf/actions/runs/33386073074