On Tue, Dec 2, 2025 at 6:20 AM Shuran Liu <[email protected]> wrote: > > Add a regression test for bpf_d_path() when invoked from an LSM program. > The test attaches to the bprm_check_security hook, calls bpf_d_path() on > the binary being executed, and verifies that a simple prefix comparison on > the returned pathname behaves correctly after the fix in patch 1. > > To avoid nondeterminism, the LSM program now filters based on the > expected PID, which is populated from userspace before the test binary is > executed. This prevents unrelated processes that also trigger the > bprm_check_security LSM hook from overwriting test results. Parent and > child processes are synchronized through a pipe to ensure the PID is set > before the child execs the test binary. > > Per review feedback, the new LSM coverage is merged into the existing > d_path selftest rather than adding new prog_tests/ or progs/ files. The > loop that checks the pathname prefix now uses bpf_for(), which is a > verifier-friendly way to express a small, fixed-iteration loop, and the > temporary /tmp/bpf_d_path_test binary is removed in the test cleanup > path. > > Co-developed-by: Zesen Liu <[email protected]> > Signed-off-by: Zesen Liu <[email protected]> > Co-developed-by: Peili Gao <[email protected]> > Signed-off-by: Peili Gao <[email protected]> > Co-developed-by: Haoran Ni <[email protected]> > Signed-off-by: Haoran Ni <[email protected]> > Signed-off-by: Shuran Liu <[email protected]> > Reviewed-by: Matt Bobrowski <[email protected]> > --- > .../testing/selftests/bpf/prog_tests/d_path.c | 65 +++++++++++++++++++ > .../testing/selftests/bpf/progs/test_d_path.c | 33 ++++++++++ > 2 files changed, 98 insertions(+) > > diff --git a/tools/testing/selftests/bpf/prog_tests/d_path.c > b/tools/testing/selftests/bpf/prog_tests/d_path.c > index ccc768592e66..202b44e6f482 100644 > --- a/tools/testing/selftests/bpf/prog_tests/d_path.c > +++ b/tools/testing/selftests/bpf/prog_tests/d_path.c > @@ -195,6 +195,68 @@ static void test_d_path_check_types(void) > test_d_path_check_types__destroy(skel); > } > > +static void test_d_path_lsm(void) > +{ > + struct test_d_path *skel; > + int err; > + int pipefd[2]; > + pid_t pid; > + > + skel = test_d_path__open_and_load(); > + if (!ASSERT_OK_PTR(skel, "d_path skeleton failed")) > + return; > + > + err = test_d_path__attach(skel); > + if (!ASSERT_OK(err, "attach failed")) > + goto cleanup; > + > + /* Prepare the test binary */ > + system("cp /bin/true /tmp/bpf_d_path_test 2>/dev/null || :"); > + > + if (!ASSERT_OK(pipe(pipefd), "pipe failed")) > + goto cleanup; > + > + pid = fork(); > + if (!ASSERT_GE(pid, 0, "fork failed")) { > + close(pipefd[0]); > + close(pipefd[1]); > + goto cleanup; > + } > + > + if (pid == 0) { > + /* Child */ > + char buf; > + > + close(pipefd[1]); > + /* Wait for parent to set PID in BPF map */ > + if (read(pipefd[0], &buf, 1) != 1) > + exit(1); > + close(pipefd[0]); > + execl("/tmp/bpf_d_path_test", "/tmp/bpf_d_path_test", NULL); > + exit(1); > + }
No forks please. They often make selftest to be flaky. Use simples possible way to test it. Without forks and pipes. pw-bot: cr
