Add a test kfunc that takes a trusted struct ns_common and check that:

- namespace_init and namespace_free arguments can't be passed to it

- namespace_install arguments can

The test fails if namespace_init and namespace_free are treated as
trusted.

Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
---
 tools/testing/selftests/bpf/prog_tests/verifier.c  |  2 ++
 .../selftests/bpf/progs/verifier_lsm_namespace.c   | 38 ++++++++++++++++++++++
 .../testing/selftests/bpf/test_kmods/bpf_testmod.c |  5 +++
 .../selftests/bpf/test_kmods/bpf_testmod_kfunc.h   |  1 +
 4 files changed, 46 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/verifier.c b/tools/testing/selftests/bpf/prog_tests/verifier.c
index 04740ba37e91..3963a4f71d98 100644
--- a/tools/testing/selftests/bpf/prog_tests/verifier.c
+++ b/tools/testing/selftests/bpf/prog_tests/verifier.c
@@ -147,6 +147,7 @@
 #include "verifier_set_retval.skel.h"
 #include "verifier_lsm.skel.h"
 #include "verifier_lsm_init_xattr.skel.h"
+#include "verifier_lsm_namespace.skel.h"
 #include "verifier_jit_inline.skel.h"
 #include "irq.skel.h"
 #include "verifier_ctx_ptr_param.skel.h"
@@ -337,6 +338,7 @@ void test_verifier_bits_iter(void) { RUN(verifier_bits_iter); }
 void test_verifier_set_retval(void)            { RUN(verifier_set_retval); }
 void test_verifier_lsm(void)                  { RUN(verifier_lsm); }
 void test_verifier_lsm_init_xattr(void)       { RUN(verifier_lsm_init_xattr); }
+void test_verifier_lsm_namespace(void)        { RUN_TESTS(verifier_lsm_namespace); }
 void test_irq(void)			      { RUN(irq); }
 void test_verifier_mtu(void)		      { RUN(verifier_mtu); }
 void test_verifier_jit_inline(void)               { RUN(verifier_jit_inline); }
diff --git a/tools/testing/selftests/bpf/progs/verifier_lsm_namespace.c b/tools/testing/selftests/bpf/progs/verifier_lsm_namespace.c
new file mode 100644
index 000000000000..d14fa2363dcc
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/verifier_lsm_namespace.c
@@ -0,0 +1,38 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <vmlinux.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+#include "bpf_misc.h"
+#include "../test_kmods/bpf_testmod_kfunc.h"
+
+/* The namespace hasn't been set up yet. */
+SEC("lsm/namespace_init")
+__failure __msg("R1 must be referenced or trusted")
+int BPF_PROG(namespace_init_untrusted, struct ns_common *ns)
+{
+	bpf_kfunc_trusted_ns_test(ns);
+	return 0;
+}
+
+/* The namespace is being torn down. */
+SEC("lsm/namespace_free")
+__failure __msg("R1 must be referenced or trusted")
+int BPF_PROG(namespace_free_untrusted, struct ns_common *ns)
+{
+	bpf_kfunc_trusted_ns_test(ns);
+	return 0;
+}
+
+/* setns() holds a reference to a fully set up namespace. */
+SEC("lsm/namespace_install")
+__success
+int BPF_PROG(namespace_install_trusted, const struct nsset *nsset,
+	     struct ns_common *ns)
+{
+	bpf_kfunc_trusted_ns_test(ns);
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";
diff --git a/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c b/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c
index 6380f52f4dd2..8d6bd2237f34 100644
--- a/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c
+++ b/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c
@@ -350,6 +350,10 @@ __bpf_kfunc void bpf_kfunc_trusted_task_test(struct task_struct *ptr)
 {
 }
 
+__bpf_kfunc void bpf_kfunc_trusted_ns_test(struct ns_common *ptr)
+{
+}
+
 __bpf_kfunc struct task_struct *bpf_kfunc_trusted_null_test(void)
 {
 	return NULL;
@@ -1030,6 +1034,7 @@ BTF_ID_FLAGS(func, bpf_kfunc_nested_acquire_zero_offset_test, KF_ACQUIRE)
 BTF_ID_FLAGS(func, bpf_kfunc_nested_release_test, KF_RELEASE)
 BTF_ID_FLAGS(func, bpf_kfunc_trusted_vma_test)
 BTF_ID_FLAGS(func, bpf_kfunc_trusted_task_test)
+BTF_ID_FLAGS(func, bpf_kfunc_trusted_ns_test)
 BTF_ID_FLAGS(func, bpf_kfunc_trusted_null_test, KF_RET_NULL)
 BTF_ID_FLAGS(func, bpf_kfunc_trusted_nullable_test)
 BTF_ID_FLAGS(func, bpf_kfunc_trusted_num_test)
diff --git a/tools/testing/selftests/bpf/test_kmods/bpf_testmod_kfunc.h b/tools/testing/selftests/bpf/test_kmods/bpf_testmod_kfunc.h
index 3b810f1e438f..bc32c4078d27 100644
--- a/tools/testing/selftests/bpf/test_kmods/bpf_testmod_kfunc.h
+++ b/tools/testing/selftests/bpf/test_kmods/bpf_testmod_kfunc.h
@@ -355,6 +355,7 @@ int bpf_kfunc_st_ops_inc10(struct st_ops_args *args) __ksym;
 
 void bpf_kfunc_trusted_vma_test(struct vm_area_struct *ptr) __ksym;
 void bpf_kfunc_trusted_task_test(struct task_struct *ptr) __ksym;
+void bpf_kfunc_trusted_ns_test(struct ns_common *ptr) __ksym;
 struct task_struct *bpf_kfunc_trusted_null_test(void) __ksym;
 void bpf_kfunc_trusted_nullable_test(struct task_struct *ptr__nullable) __ksym;
 void bpf_kfunc_trusted_num_test(int *ptr) __ksym;

-- 
2.53.0