selftests/bpf: Add tests for BPF object load with implicit token

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.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20240124022127.2379740-28-andrii@kernel.org

diff --git a/tools/testing/selftests/bpf/prog_tests/token.c b/tools/testing/selftests/bpf/prog_tests/token.c
index 1594d9b..003f7c2 100644 (file)
--- 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);
+       }
 }