[PATCH bpf-next 4/5] selftests/bpf: add a selftest with __user tag

[Yonghong Song <yhs@fb.com>]

Added a selftest with two __user usages: a __user pointer-type argument
and a __user pointer-type struct member. In both cases,
directly accessing the user memory will result verification failure.

  $ ./test_progs -v -n 22/3
  ...
  libbpf: load bpf program failed: Permission denied
  libbpf: -- BEGIN DUMP LOG ---
  libbpf:
  R1 type=ctx expected=fp
  ; int BPF_PROG(test_user1, struct bpf_testmod_btf_type_tag_1 *arg)
  0: (79) r1 = *(u64 *)(r1 +0)
  func 'bpf_testmod_test_btf_type_tag_user_1' arg0 has btf_id 143948 addr_space 1 type STRUCT 'bpf_testmod_btf_type_tag_1'
  ; g = arg->a;
  1: (61) r1 = *(u32 *)(r1 +0)
  R1 is ptr_bpf_testmod_btf_type_tag_1 access user memory: off=0
  ...
  #22/3 btf_tag/btf_type_tag_user_1:OK

  $ ./test_progs -v -n 22/4
  ...
  libbpf: load bpf program failed: Permission denied
  libbpf: -- BEGIN DUMP LOG ---
  libbpf:
  R1 type=ctx expected=fp
  ; int BPF_PROG(test_user2, struct bpf_testmod_btf_type_tag_2 *arg)
  0: (79) r1 = *(u64 *)(r1 +0)
  func 'bpf_testmod_test_btf_type_tag_user_2' arg0 has btf_id 143950 addr_space 0 type STRUCT 'bpf_testmod_btf_type_tag_2'
  ; g = arg->p->a;
  1: (79) r1 = *(u64 *)(r1 +0)
  ; g = arg->p->a;
  2: (61) r1 = *(u32 *)(r1 +0)
  R1 is ptr_bpf_testmod_btf_type_tag_1 access user memory: off=0
  ...
  #22/4 btf_tag/btf_type_tag_user_2:OK

Signed-off-by: Yonghong Song <yhs@fb.com>
---
 .../selftests/bpf/bpf_testmod/bpf_testmod.c   | 18 ++++++
 .../selftests/bpf/prog_tests/btf_tag.c        | 55 +++++++++++++++++++
 .../selftests/bpf/progs/btf_type_tag_user.c   | 29 ++++++++++
 3 files changed, 102 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/progs/btf_type_tag_user.c

diff --git a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
index 5d52ea2768df..119fd5ba7ce4 100644
--- a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
+++ b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
@@ -21,6 +21,24 @@ bpf_testmod_test_mod_kfunc(int i)
 	*(int *)this_cpu_ptr(&bpf_testmod_ksym_percpu) = i;
 }
 
+struct bpf_testmod_btf_type_tag_1 {
+	int a;
+};
+
+struct bpf_testmod_btf_type_tag_2 {
+	struct bpf_testmod_btf_type_tag_1 __user *p;
+};
+
+noinline int
+bpf_testmod_test_btf_type_tag_user_1(struct bpf_testmod_btf_type_tag_1 __user *arg) {
+	return arg->a;
+}
+
+noinline int
+bpf_testmod_test_btf_type_tag_user_2(struct bpf_testmod_btf_type_tag_2 *arg) {
+	return arg->p->a;
+}
+
 noinline int bpf_testmod_loop_test(int n)
 {
 	int i, sum = 0;
diff --git a/tools/testing/selftests/bpf/prog_tests/btf_tag.c b/tools/testing/selftests/bpf/prog_tests/btf_tag.c
index c4cf27777ff7..794752265ede 100644
--- a/tools/testing/selftests/bpf/prog_tests/btf_tag.c
+++ b/tools/testing/selftests/bpf/prog_tests/btf_tag.c
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0
 /* Copyright (c) 2021 Facebook */
 #include <test_progs.h>
+#include <bpf/btf.h>
 #include "test_btf_decl_tag.skel.h"
 
 /* struct btf_type_tag_test is referenced in btf_type_tag.skel.h */
@@ -8,6 +9,7 @@ struct btf_type_tag_test {
         int **p;
 };
 #include "btf_type_tag.skel.h"
+#include "btf_type_tag_user.skel.h"
 
 static void test_btf_decl_tag(void)
 {
@@ -41,10 +43,63 @@ static void test_btf_type_tag(void)
 	btf_type_tag__destroy(skel);
 }
 
+static void test_btf_type_tag_user(bool load_test_user1)
+{
+	const char *module_name = "bpf_testmod";
+	struct btf *vmlinux_btf, *module_btf;
+	struct btf_type_tag_user *skel;
+	__s32 type_id;
+	int err;
+
+	if (!env.has_testmod) {
+		test__skip();
+		return;
+	}
+
+	/* skip the test is the module does not have __user tags */
+	vmlinux_btf = btf__load_vmlinux_btf();
+	if (!ASSERT_OK_PTR(vmlinux_btf, "could not load vmlinux BTF"))
+		return;
+
+	module_btf = btf__load_module_btf(module_name, vmlinux_btf);
+	if (!ASSERT_OK_PTR(module_btf, "could not load module BTF"))
+		goto free_vmlinux_btf;
+
+	type_id = btf__find_by_name_kind(module_btf, "user", BTF_KIND_TYPE_TAG);
+	if (type_id <= 0) {
+		printf("%s:SKIP: btf_type_tag attribute not in %s", __func__, module_name);
+		test__skip();
+		goto free_module_btf;
+	}
+
+	skel = btf_type_tag_user__open();
+	if (!ASSERT_OK_PTR(skel, "btf_type_tag_user"))
+		goto free_module_btf;
+
+	if (load_test_user1)
+		bpf_program__set_autoload(skel->progs.test_user2, false);
+	else
+		bpf_program__set_autoload(skel->progs.test_user1, false);
+
+	err = btf_type_tag_user__load(skel);
+	ASSERT_ERR(err, "btf_type_tag_user");
+
+	btf_type_tag_user__destroy(skel);
+
+free_module_btf:
+	btf__free(module_btf);
+free_vmlinux_btf:
+	btf__free(vmlinux_btf);
+}
+
 void test_btf_tag(void)
 {
 	if (test__start_subtest("btf_decl_tag"))
 		test_btf_decl_tag();
 	if (test__start_subtest("btf_type_tag"))
 		test_btf_type_tag();
+	if (test__start_subtest("btf_type_tag_user_1"))
+		test_btf_type_tag_user(true);
+	if (test__start_subtest("btf_type_tag_user_2"))
+		test_btf_type_tag_user(false);
 }
diff --git a/tools/testing/selftests/bpf/progs/btf_type_tag_user.c b/tools/testing/selftests/bpf/progs/btf_type_tag_user.c
new file mode 100644
index 000000000000..e149854f42dd
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/btf_type_tag_user.c
@@ -0,0 +1,29 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Facebook */
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+struct bpf_testmod_btf_type_tag_1 {
+	int a;
+};
+
+struct bpf_testmod_btf_type_tag_2 {
+	struct bpf_testmod_btf_type_tag_1 *p;
+};
+
+int g;
+
+SEC("fentry/bpf_testmod_test_btf_type_tag_user_1")
+int BPF_PROG(test_user1, struct bpf_testmod_btf_type_tag_1 *arg)
+{
+	g = arg->a;
+	return 0;
+}
+
+SEC("fentry/bpf_testmod_test_btf_type_tag_user_2")
+int BPF_PROG(test_user2, struct bpf_testmod_btf_type_tag_2 *arg)
+{
+	g = arg->p->a;
+	return 0;
+}
-- 
2.30.2