[PATCH v4 bpf-next 14/14] selftests/bpf: Add negative tests for bpf_nf

[Lorenzo Bianconi <lorenzo@kernel.org>]

From: Kumar Kartikeya Dwivedi <memxor@gmail.com>

Test cases we care about and ensure improper usage is caught and
rejected by verifier. This also ends up exercising acquire release
pair logic and MEM_RDONLY's effect on a PTR_TO_BTF_ID which usually
permits BPF_WRITE.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
---
 .../testing/selftests/bpf/prog_tests/bpf_nf.c | 52 ++++++++++++-
 .../selftests/bpf/progs/test_bpf_nf_fail.c    | 73 +++++++++++++++++++
 2 files changed, 124 insertions(+), 1 deletion(-)
 create mode 100644 tools/testing/selftests/bpf/progs/test_bpf_nf_fail.c

diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_nf.c b/tools/testing/selftests/bpf/prog_tests/bpf_nf.c
index b909928427f3..d7294c6451d0 100644
--- a/tools/testing/selftests/bpf/prog_tests/bpf_nf.c
+++ b/tools/testing/selftests/bpf/prog_tests/bpf_nf.c
@@ -2,13 +2,25 @@
 #include <test_progs.h>
 #include <network_helpers.h>
 #include "test_bpf_nf.skel.h"
+#include "test_bpf_nf_fail.skel.h"
+
+static char log_buf[1024 * 1024];
+
+struct {
+	const char *prog_name;
+	const char *err_msg;
+} test_bpf_nf_fail_tests[] = {
+	{ "alloc_release", "not permitted to release reference" },
+	{ "write_after_insert", "pointer points to const object, only read is supported" },
+	{ "lookup_insert", "cannot pass read only pointer to arg#0" },
+};
 
 enum {
 	TEST_XDP,
 	TEST_TC_BPF,
 };
 
-void test_bpf_nf_ct(int mode)
+static void test_bpf_nf_ct(int mode)
 {
 	struct test_bpf_nf *skel;
 	int prog_fd, err;
@@ -49,10 +61,48 @@ void test_bpf_nf_ct(int mode)
 	test_bpf_nf__destroy(skel);
 }
 
+static void test_bpf_nf_ct_fail(const char *prog_name, const char *err_msg)
+{
+	LIBBPF_OPTS(bpf_object_open_opts, opts, .kernel_log_buf = log_buf,
+						.kernel_log_size = sizeof(log_buf),
+						.kernel_log_level = 1);
+	struct test_bpf_nf_fail *skel;
+	struct bpf_program *prog;
+	int ret;
+
+	skel = test_bpf_nf_fail__open_opts(&opts);
+	if (!ASSERT_OK_PTR(skel, "test_bpf_nf_fail__open"))
+		return;
+
+	prog = bpf_object__find_program_by_name(skel->obj, prog_name);
+	if (!ASSERT_OK_PTR(prog, "bpf_object__find_program_by_name"))
+		goto end;
+
+	bpf_program__set_autoload(prog, true);
+
+	ret = test_bpf_nf_fail__load(skel);
+	if (!ASSERT_ERR(ret, "test_bpf_nf_fail__load must fail"))
+		goto end;
+
+	if (!ASSERT_OK_PTR(strstr(log_buf, err_msg), "expected error message")) {
+		fprintf(stderr, "Expected: %s\n", err_msg);
+		fprintf(stderr, "Verifier: %s\n", log_buf);
+	}
+
+end:
+	test_bpf_nf_fail__destroy(skel);
+}
+
 void test_bpf_nf(void)
 {
+	int i;
 	if (test__start_subtest("xdp-ct"))
 		test_bpf_nf_ct(TEST_XDP);
 	if (test__start_subtest("tc-bpf-ct"))
 		test_bpf_nf_ct(TEST_TC_BPF);
+	for (i = 0; i < ARRAY_SIZE(test_bpf_nf_fail_tests); i++) {
+		if (test__start_subtest(test_bpf_nf_fail_tests[i].prog_name))
+			test_bpf_nf_ct_fail(test_bpf_nf_fail_tests[i].prog_name,
+					    test_bpf_nf_fail_tests[i].err_msg);
+	}
 }
diff --git a/tools/testing/selftests/bpf/progs/test_bpf_nf_fail.c b/tools/testing/selftests/bpf/progs/test_bpf_nf_fail.c
new file mode 100644
index 000000000000..2484f7baef90
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_bpf_nf_fail.c
@@ -0,0 +1,73 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <vmlinux.h>
+#include <bpf/bpf_tracing.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_core_read.h>
+
+struct nf_conn;
+
+struct nf_conn___local {;
+	unsigned long status;
+} __attribute__((preserve_access_index));
+
+struct bpf_ct_opts___local {
+	s32 netns_id;
+	s32 error;
+	u8 l4proto;
+	u8 reserved[3];
+} __attribute__((preserve_access_index));
+
+struct nf_conn *bpf_skb_ct_alloc(struct __sk_buff *, struct bpf_sock_tuple *, u32,
+				 struct bpf_ct_opts___local *, u32) __ksym;
+const struct nf_conn *bpf_skb_ct_lookup(struct __sk_buff *, struct bpf_sock_tuple *, u32,
+					struct bpf_ct_opts___local *, u32) __ksym;
+const struct nf_conn *
+bpf_ct_insert_entry(struct nf_conn *, struct bpf_ct_opts___local *, u32) __ksym;
+void bpf_ct_release(const struct nf_conn *) __ksym;
+
+SEC("?tc")
+int alloc_release(struct __sk_buff *ctx)
+{
+	struct bpf_ct_opts___local opts = {};
+	struct bpf_sock_tuple tup = {};
+	struct nf_conn *ct;
+
+	ct = bpf_skb_ct_alloc(ctx, &tup, sizeof(tup.ipv4), &opts, sizeof(opts));
+	if (!ct)
+		return 0;
+	bpf_ct_release(ct);
+	return 0;
+}
+
+SEC("?tc")
+int write_after_insert(struct __sk_buff *ctx)
+{
+	struct bpf_ct_opts___local opts = {};
+	struct bpf_sock_tuple tup = {};
+	struct nf_conn___local *ct;
+
+	ct = (void *)bpf_skb_ct_alloc(ctx, &tup, sizeof(tup.ipv4), &opts, sizeof(opts));
+	if (!ct)
+		return 0;
+	ct = (void *)bpf_ct_insert_entry((void *)ct, &opts, sizeof(opts));
+	if (!ct)
+		return 0;
+	ct->status = 0;
+	return 0;
+}
+
+SEC("?tc")
+int lookup_insert(struct __sk_buff *ctx)
+{
+	struct bpf_ct_opts___local opts = {};
+	struct bpf_sock_tuple tup = {};
+	struct nf_conn *ct;
+
+	ct = (void *)bpf_skb_ct_lookup(ctx, &tup, sizeof(tup.ipv4), &opts, sizeof(opts));
+	if (!ct)
+		return 0;
+	bpf_ct_insert_entry(ct, &opts, sizeof(opts));
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";
-- 
2.35.3