[PATCH bpf-next 27/29] selftests/bpf: add tests for BPF object load with implicit token

Andrii Nakryiko
2024-01-03T22:25:18Z

Add a test to validate libbpf's implicit BPF token creation from default
BPF FS location (/sys/fs/bpf). Also validate that disabling this
implicit BPF token creation works.

Acked-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
---
.../testing/selftests/bpf/prog_tests/token.c | 64 +++++++++++++++++++
1 file changed, 64 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/token.c b/tools/testing/selftests/bpf/prog_tests/token.c
index 1594d9b94b13..003f7c208f4c 100644
--- a/tools/testing/selftests/bpf/prog_tests/token.c
+++ b/tools/testing/selftests/bpf/prog_tests/token.c
@@ -12,6 +12,7 @@
#include <linux/unistd.h>
#include <linux/mount.h>
#include <sys/socket.h>
+#include <sys/stat.h>
#include <sys/syscall.h>
#include <sys/un.h>
#include "priv_map.skel.h"
@@ -45,6 +46,13 @@ static inline int sys_fsmount(int fs_fd, unsigned flags, unsigned ms_flags)
return syscall(__NR_fsmount, fs_fd, flags, ms_flags);
}

+static inline int sys_move_mount(int from_dfd, const char *from_path,
+ int to_dfd, const char *to_path,
+ unsigned flags)
+{
+ return syscall(__NR_move_mount, from_dfd, from_path, to_dfd, to_path, flags);
+}
+
static int drop_priv_caps(__u64 *old_caps)
{
return cap_disable_effective((1ULL << CAP_BPF) |
@@ -765,6 +773,51 @@ static int userns_obj_priv_btf_success(int mnt_fd)
return validate_struct_ops_load(mnt_fd, true /* should succeed */);
}

+static int userns_obj_priv_implicit_token(int mnt_fd)
+{
+ LIBBPF_OPTS(bpf_object_open_opts, opts);
+ struct dummy_st_ops_success *skel;
+ int err;
+
+ /* before we mount BPF FS with token delegation, struct_ops skeleton
+ * should fail to load
+ */
+ skel = dummy_st_ops_success__open_and_load();
+ if (!ASSERT_ERR_PTR(skel, "obj_tokenless_load")) {
+ dummy_st_ops_success__destroy(skel);
+ return -EINVAL;
+ }
+
+ /* mount custom BPF FS over /sys/fs/bpf so that libbpf can create BPF
+ * token automatically and implicitly
+ */
+ err = sys_move_mount(mnt_fd, "", AT_FDCWD, "/sys/fs/bpf", MOVE_MOUNT_F_EMPTY_PATH);
+ if (!ASSERT_OK(err, "move_mount_bpffs"))
+ return -EINVAL;
+
+ /* now the same struct_ops skeleton should succeed thanks to libppf
+ * creating BPF token from /sys/fs/bpf mount point
+ */
+ skel = dummy_st_ops_success__open_and_load();
+ if (!ASSERT_OK_PTR(skel, "obj_implicit_token_load"))
+ return -EINVAL;
+
+ dummy_st_ops_success__destroy(skel);
+
+ /* now disable implicit token through empty bpf_token_path, should fail */
+ opts.bpf_token_path = "";
+ skel = dummy_st_ops_success__open_opts(&opts);
+ if (!ASSERT_OK_PTR(skel, "obj_empty_token_path_open"))
+ return -EINVAL;
+
+ err = dummy_st_ops_success__load(skel);
+ dummy_st_ops_success__destroy(skel);
+ if (!ASSERT_ERR(err, "obj_empty_token_path_load"))
+ return -EINVAL;
+
+ return 0;
+}
+
#define bit(n) (1ULL << (n))

void test_token(void)
@@ -832,4 +885,15 @@ void test_token(void)

subtest_userns(&opts, userns_obj_priv_btf_success);
}
+ if (test__start_subtest("obj_priv_implicit_token")) {
+ struct bpffs_opts opts = {
+ /* allow BTF loading */
+ .cmds = bit(BPF_BTF_LOAD) | bit(BPF_MAP_CREATE) | bit(BPF_PROG_LOAD),
+ .maps = bit(BPF_MAP_TYPE_STRUCT_OPS),
+ .progs = bit(BPF_PROG_TYPE_STRUCT_OPS),
+ .attachs = ~0ULL,
+ };
+
+ subtest_userns(&opts, userns_obj_priv_implicit_token);
+ }
}
--
2.34.1