selftests/bpf: Fix memory leaks in btf_type_c_dump() helper

mainline inclusion
from mainline-5.17-rc1
commit 8ba28587
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I5EUVD
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=8ba285874913da21ca39a46376e9cc5ce0f45f94

-------------------------------------------------

Free up memory and resources used by temporary allocated memstream and
btf_dump instance.
Signed-off-by: NAndrii Nakryiko <andrii@kernel.org>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>
Reviewed-by: NHengqi Chen <hengqi.chen@gmail.com>
Link: https://lore.kernel.org/bpf/20211107165521.9240-4-andrii@kernel.org
(cherry picked from commit 8ba28587)
Signed-off-by: NWang Yufen <wangyufen@huawei.com>

tools/testing/selftests/bpf/btf_helpers.c

@@ -242,18 +242,23 @@ const char *btf_type_c_dump(const struct btf *btf)
 	d = btf_dump__new(btf, NULL, &opts, btf_dump_printf);
 	if (libbpf_get_error(d)) {
 		fprintf(stderr, "Failed to create btf_dump instance: %ld\n", libbpf_get_error(d));
-		return NULL;
+		goto err_out;
 	}
 
 	for (i = 1; i <= btf__get_nr_types(btf); i++) {
 		err = btf_dump__dump_type(d, i);
 		if (err) {
 			fprintf(stderr, "Failed to dump type [%d]: %d\n", i, err);
-			return NULL;
+			goto err_out;
 		}
 	}
 
+	btf_dump__free(d);
 	fflush(buf_file);
 	fclose(buf_file);
 	return buf;
+err_out:
+	btf_dump__free(d);
+	fclose(buf_file);
+	return NULL;
 }