Add selftests that goes over every known map type and validates that
a combination of privileged/unprivileged modes and allow/reject/pass-through
LSM policy decisions behave as expected.
Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
---
.../selftests/bpf/prog_tests/lsm_map_create.c | 143 ++++++++++++++++++
.../selftests/bpf/progs/lsm_map_create.c | 32 ++++
tools/testing/selftests/bpf/test_progs.h | 6 +
3 files changed, 181 insertions(+)
create mode 100644 tools/testing/selftests/bpf/prog_tests/lsm_map_create.c
create mode 100644 tools/testing/selftests/bpf/progs/lsm_map_create.c
diff --git a/tools/testing/selftests/bpf/prog_tests/lsm_map_create.c b/tools/testing/selftests/bpf/prog_tests/lsm_map_create.c
new file mode 100644
index 000000000000..fee78b0448c3
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/lsm_map_create.c
@@ -0,0 +1,143 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2023 Meta Platforms, Inc. and affiliates. */
+#include "linux/bpf.h"
+#include <test_progs.h>
+#include <bpf/btf.h>
+#include "cap_helpers.h"
+#include "lsm_map_create.skel.h"
+
+static int drop_priv_caps(__u64 *old_caps)
+{
+ return cap_disable_effective((1ULL << CAP_BPF) |
+ (1ULL << CAP_PERFMON) |
+ (1ULL << CAP_NET_ADMIN) |
+ (1ULL << CAP_SYS_ADMIN), old_caps);
+}
+
+static int restore_priv_caps(__u64 old_caps)
+{
+ return cap_enable_effective(old_caps, NULL);
+}
+
+void test_lsm_map_create(void)
+{
+ struct btf *btf = NULL;
+ struct lsm_map_create *skel = NULL;
+ const struct btf_type *t;
+ const struct btf_enum *e;
+ int i, n, id, err, ret;
+
+ skel = lsm_map_create__open_and_load();
+ if (!ASSERT_OK_PTR(skel, "skel_open_and_load"))
+ return;
+
+ skel->bss->my_tid = syscall(SYS_gettid);
+ skel->bss->decision = 0;
+
+ err = lsm_map_create__attach(skel);
+ if (!ASSERT_OK(err, "skel_attach"))
+ goto cleanup;
+
+ btf = btf__parse("/sys/kernel/btf/vmlinux", NULL);
+ if (!ASSERT_OK_PTR(btf, "btf_parse"))
+ goto cleanup;
+
+ /* find enum bpf_map_type and enumerate each value */
+ id = btf__find_by_name_kind(btf, "bpf_map_type", BTF_KIND_ENUM);
+ if (!ASSERT_GT(id, 0, "bpf_map_type_id"))
+ goto cleanup;
+
+ t = btf__type_by_id(btf, id);
+ e = btf_enum(t);
+ n = btf_vlen(t);
+ for (i = 0; i < n; e++, i++) {
+ enum bpf_map_type map_type = (enum bpf_map_type)e->val;
+ const char *map_type_name;
+ __u64 orig_caps;
+ bool is_map_priv;
+ bool needs_btf;
+
+ if (map_type == BPF_MAP_TYPE_UNSPEC)
+ continue;
+
+ /* this will show which map type we are working with in verbose log */
+ map_type_name = btf__str_by_offset(btf, e->name_off);
+ ASSERT_OK_PTR(map_type_name, map_type_name);
+
+ switch (map_type) {
+ case BPF_MAP_TYPE_ARRAY:
+ case BPF_MAP_TYPE_PERCPU_ARRAY:
+ case BPF_MAP_TYPE_PROG_ARRAY:
+ case BPF_MAP_TYPE_PERF_EVENT_ARRAY:
+ case BPF_MAP_TYPE_CGROUP_ARRAY:
+ case BPF_MAP_TYPE_ARRAY_OF_MAPS:
+ case BPF_MAP_TYPE_HASH:
+ case BPF_MAP_TYPE_PERCPU_HASH:
+ case BPF_MAP_TYPE_HASH_OF_MAPS:
+ case BPF_MAP_TYPE_RINGBUF:
+ case BPF_MAP_TYPE_USER_RINGBUF:
+ case BPF_MAP_TYPE_CGROUP_STORAGE:
+ case BPF_MAP_TYPE_PERCPU_CGROUP_STORAGE:
+ is_map_priv = false;
+ needs_btf = false;
+ break;
+ case BPF_MAP_TYPE_SK_STORAGE:
+ case BPF_MAP_TYPE_INODE_STORAGE:
+ case BPF_MAP_TYPE_TASK_STORAGE:
+ case BPF_MAP_TYPE_CGRP_STORAGE:
+ is_map_priv = true;
+ needs_btf = true;
+ break;
+ default:
+ is_map_priv = true;
+ needs_btf = false;
+ }
+
+ /* make sure we delegate to kernel for final decision */
+ skel->bss->decision = 0;
+
+ /* we are normally under sudo, so all maps should succeed */
+ ret = libbpf_probe_bpf_map_type(map_type, NULL);
+ ASSERT_EQ(ret, 1, "default_priv_mode");
+
+ /* local storage needs custom BTF to be loaded, which we
+ * currently can't do once we drop privileges, so skip few
+ * checks for such maps
+ */
+ if (needs_btf)
+ goto skip_if_needs_btf;
+
+ /* now let's drop privileges, and chech that unpriv maps are
+ * still possible to create
+ */
+ if (!ASSERT_OK(drop_priv_caps(&orig_caps), "drop_caps"))
+ goto cleanup;
+
+ ret = libbpf_probe_bpf_map_type(map_type, NULL);
+ ASSERT_EQ(ret, is_map_priv ? 0 : 1, "default_unpriv_mode");
+
+ /* allow any map creation for our thread */
+ skel->bss->decision = 1;
+ ret = libbpf_probe_bpf_map_type(map_type, NULL);
+ ASSERT_EQ(ret, 1, "lsm_allow_unpriv_mode");
+
+ /* reject any map creation for our thread */
+ skel->bss->decision = -1;
+ ret = libbpf_probe_bpf_map_type(map_type, NULL);
+ ASSERT_EQ(ret, 0, "lsm_reject_unpriv_mode");
+
+ /* restore privileges, but keep reject LSM policy */
+ if (!ASSERT_OK(restore_priv_caps(orig_caps), "restore_caps"))
+ goto cleanup;
+
+skip_if_needs_btf:
+ /* even with all caps map create will fail */
+ skel->bss->decision = -1;
+ ret = libbpf_probe_bpf_map_type(map_type, NULL);
+ ASSERT_EQ(ret, 0, "lsm_reject_priv_mode");
+ }
+
+cleanup:
+ btf__free(btf);
+ lsm_map_create__destroy(skel);
+}
diff --git a/tools/testing/selftests/bpf/progs/lsm_map_create.c b/tools/testing/selftests/bpf/progs/lsm_map_create.c
new file mode 100644
index 000000000000..093825c68459
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/lsm_map_create.c
@@ -0,0 +1,32 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2023 Meta Platforms, Inc. and affiliates. */
+
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include <errno.h>
+
+char _license[] SEC("license") = "GPL";
+
+int my_tid;
+/* LSM enforcement:
+ * - 0, delegate to kernel;
+ * - 1, allow;
+ * - -1, reject.
+ */
+int decision;
+
+SEC("lsm/bpf_map_create_security")
+int BPF_PROG(allow_unpriv_maps, union bpf_attr *attr)
+{
+ if (!my_tid || (u32)bpf_get_current_pid_tgid() != my_tid)
+ return 0; /* keep processing LSM hooks */
+
+ if (decision == 0)
+ return 0;
+
+ if (decision > 0)
+ return 1; /* allow */
+
+ return -EPERM;
+}
diff --git a/tools/testing/selftests/bpf/test_progs.h b/tools/testing/selftests/bpf/test_progs.h
index 10ba43250668..12f9c6652d40 100644
--- a/tools/testing/selftests/bpf/test_progs.h
+++ b/tools/testing/selftests/bpf/test_progs.h
@@ -23,6 +23,7 @@ typedef __u16 __sum16;
#include <linux/perf_event.h>
#include <linux/socket.h>
#include <linux/unistd.h>
+#include <sys/syscall.h>
#include <sys/ioctl.h>
#include <sys/wait.h>
@@ -176,6 +177,11 @@ void test__skip(void);
void test__fail(void);
int test__join_cgroup(const char *path);
+static inline int gettid(void)
+{
+ return syscall(SYS_gettid);
+}
+
#define PRINT_FAIL(format...) \
({ \
test__fail(); \
--
2.34.1
