Create a hash and an rhash map with btf_key_type_id == 0 and expect bpf_map_create() to fail with -EINVAL; a positive control with a real key type confirms the rejection is about the key-less BTF. On an unfixed kernel the map is created, and the test pins and reads it back to walk the bpffs dump path, which reproduces the btf_type_show() NULL-deref - so running it on an unfixed kernel oopses the reading task (and panics it under panic_on_oops).
Signed-off-by: Jiayuan Chen <[email protected]> --- .../bpf/prog_tests/btf_map_keyless.c | 83 +++++++++++++++++++ 1 file changed, 83 insertions(+) create mode 100644 tools/testing/selftests/bpf/prog_tests/btf_map_keyless.c diff --git a/tools/testing/selftests/bpf/prog_tests/btf_map_keyless.c b/tools/testing/selftests/bpf/prog_tests/btf_map_keyless.c new file mode 100644 index 000000000000..43f0bb9bd578 --- /dev/null +++ b/tools/testing/selftests/bpf/prog_tests/btf_map_keyless.c @@ -0,0 +1,83 @@ +// SPDX-License-Identifier: GPL-2.0 +#define _GNU_SOURCE +#include <test_progs.h> +#include <bpf/btf.h> + +/* + * A hash map with a key-less BTF (btf_key_type_id == 0) used to NULL-deref in + * btf_type_show() when dumped via bpffs. + * A fixed kernel rejects such a map at creation; on an unfixed kernel the + * pin-and-read below deliberately walks that bpffs dump path, so it doubles + * as a reproducer: it oopses an unfixed kernel (and panics it under + * panic_on_oops). + */ +static void check_keyless(int map_type, __u32 map_flags, int btf_fd, int val_id) +{ + LIBBPF_OPTS(bpf_map_create_opts, opts); + const char *path = "/sys/fs/bpf/keyless_map"; + __u32 key = 1, val = 0x41424344; + char buf[256]; + int map_fd; + FILE *f; + + opts.map_flags = map_flags; + opts.btf_fd = btf_fd; + opts.btf_value_type_id = val_id; + + /* + * Positive control: the same map with a real key type must be accepted, + * so the -EINVAL below is about the key-less BTF and not some unrelated + * rejection (e.g. an unknown map type). + */ + opts.btf_key_type_id = val_id; + map_fd = bpf_map_create(map_type, "keyed_map", 4, 4, 8, &opts); + if (!ASSERT_GE(map_fd, 0, "keyed create is accepted")) + return; + close(map_fd); + + /* A key-less BTF must be rejected. */ + opts.btf_key_type_id = 0; + map_fd = bpf_map_create(map_type, "keyless_map", 4, 4, 8, &opts); + + if (map_fd >= 0) { + /* Unfixed kernel: reproduce the oops via the bpffs dump path. */ + (void)bpf_map_update_elem(map_fd, &key, &val, 0); + if (bpf_obj_pin(map_fd, path) == 0) { + f = fopen(path, "r"); + if (f) { + while (fgets(buf, sizeof(buf), f)) + ; + fclose(f); + } + unlink(path); + } + close(map_fd); + } + + ASSERT_EQ(map_fd, -EINVAL, "key-less create is rejected"); +} + +void test_btf_map_keyless(void) +{ + int btf_fd, val_id; + struct btf *btf; + + btf = btf__new_empty(); + if (!ASSERT_OK_PTR(btf, "btf__new_empty")) + return; + + val_id = btf__add_int(btf, "int", 4, BTF_INT_SIGNED); + if (!ASSERT_GT(val_id, 0, "btf__add_int")) + goto out; + + if (!ASSERT_OK(btf__load_into_kernel(btf), "btf__load_into_kernel")) + goto out; + btf_fd = btf__fd(btf); + + if (test__start_subtest("hash")) + check_keyless(BPF_MAP_TYPE_HASH, 0, btf_fd, val_id); + if (test__start_subtest("rhash")) + check_keyless(BPF_MAP_TYPE_RHASH, BPF_F_NO_PREALLOC, btf_fd, val_id); +out: + btf__free(btf); +} -- 2.43.0
