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Message-Id: <20240510192412.3297104-3-amery.hung@bytedance.com>
Date: Fri, 10 May 2024 19:23:54 +0000
From: Amery Hung <ameryhung@...il.com>
To: netdev@...r.kernel.org
Cc: bpf@...r.kernel.org,
yangpeihao@...u.edu.cn,
daniel@...earbox.net,
andrii@...nel.org,
martin.lau@...nel.org,
sinquersw@...il.com,
toke@...hat.com,
jhs@...atatu.com,
jiri@...nulli.us,
sdf@...gle.com,
xiyou.wangcong@...il.com,
yepeilin.cs@...il.com,
ameryhung@...il.com
Subject: [RFC PATCH v8 02/20] selftests/bpf: Test referenced kptr arguments of struct_ops programs
A reference is automatically acquired for a referenced kptr argument
annotated via the stub function with "__ref_acquired" in a struct_ops
program. It must be released and cannot be acquired more than once.
The test first checks whether a reference to the correct type is acquired
in "ref_acquire". Then, we check if the verifier correctly rejects the
program that fails to release the reference (i.e., reference leak) in
"ref_acquire_ref_leak". Finally, we check if the reference can be only
acquired once through the argument in "ref_acquire_dup_ref".
Signed-off-by: Amery Hung <amery.hung@...edance.com>
---
.../selftests/bpf/bpf_testmod/bpf_testmod.c | 7 +++
.../selftests/bpf/bpf_testmod/bpf_testmod.h | 2 +
.../prog_tests/test_struct_ops_ref_acquire.c | 58 +++++++++++++++++++
.../bpf/progs/struct_ops_ref_acquire.c | 27 +++++++++
.../progs/struct_ops_ref_acquire_dup_ref.c | 24 ++++++++
.../progs/struct_ops_ref_acquire_ref_leak.c | 19 ++++++
6 files changed, 137 insertions(+)
create mode 100644 tools/testing/selftests/bpf/prog_tests/test_struct_ops_ref_acquire.c
create mode 100644 tools/testing/selftests/bpf/progs/struct_ops_ref_acquire.c
create mode 100644 tools/testing/selftests/bpf/progs/struct_ops_ref_acquire_dup_ref.c
create mode 100644 tools/testing/selftests/bpf/progs/struct_ops_ref_acquire_ref_leak.c
diff --git a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
index 39ad96a18123..64dcab25b539 100644
--- a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
+++ b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
@@ -594,10 +594,17 @@ static int bpf_testmod_ops__test_maybe_null(int dummy,
return 0;
}
+static int bpf_testmod_ops__test_ref_acquire(int dummy,
+ struct task_struct *task__ref_acquired)
+{
+ return 0;
+}
+
static struct bpf_testmod_ops __bpf_testmod_ops = {
.test_1 = bpf_testmod_test_1,
.test_2 = bpf_testmod_test_2,
.test_maybe_null = bpf_testmod_ops__test_maybe_null,
+ .test_ref_acquire = bpf_testmod_ops__test_ref_acquire,
};
struct bpf_struct_ops bpf_bpf_testmod_ops = {
diff --git a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.h b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.h
index 23fa1872ee67..a0233990fb0e 100644
--- a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.h
+++ b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.h
@@ -35,6 +35,8 @@ struct bpf_testmod_ops {
void (*test_2)(int a, int b);
/* Used to test nullable arguments. */
int (*test_maybe_null)(int dummy, struct task_struct *task);
+ /* Used to test ref_acquired arguments. */
+ int (*test_ref_acquire)(int dummy, struct task_struct *task);
/* The following fields are used to test shadow copies. */
char onebyte;
diff --git a/tools/testing/selftests/bpf/prog_tests/test_struct_ops_ref_acquire.c b/tools/testing/selftests/bpf/prog_tests/test_struct_ops_ref_acquire.c
new file mode 100644
index 000000000000..779287a00ed8
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/test_struct_ops_ref_acquire.c
@@ -0,0 +1,58 @@
+#include <test_progs.h>
+
+#include "struct_ops_ref_acquire.skel.h"
+#include "struct_ops_ref_acquire_ref_leak.skel.h"
+#include "struct_ops_ref_acquire_dup_ref.skel.h"
+
+/* Test that the verifier accepts a program that acquires a referenced
+ * kptr and releases the reference
+ */
+static void ref_acquire(void)
+{
+ struct struct_ops_ref_acquire *skel;
+
+ skel = struct_ops_ref_acquire__open_and_load();
+ if (!ASSERT_OK_PTR(skel, "struct_ops_module_open_and_load"))
+ return;
+
+ struct_ops_ref_acquire__destroy(skel);
+}
+
+/* Test that the verifier rejects a program that acquires a referenced
+ * kptr without releasing the reference
+ */
+static void ref_acquire_ref_leak(void)
+{
+ struct struct_ops_ref_acquire_ref_leak *skel;
+
+ skel = struct_ops_ref_acquire_ref_leak__open_and_load();
+ if (ASSERT_ERR_PTR(skel, "struct_ops_module_fail__open_and_load"))
+ return;
+
+ struct_ops_ref_acquire_ref_leak__destroy(skel);
+}
+
+/* Test that the verifier rejects a program that tries to acquire a
+ * referenced twice
+ */
+static void ref_acquire_dup_ref(void)
+{
+ struct struct_ops_ref_acquire_dup_ref *skel;
+
+ skel = struct_ops_ref_acquire_dup_ref__open_and_load();
+ if (ASSERT_ERR_PTR(skel, "struct_ops_module_fail__open_and_load"))
+ return;
+
+ struct_ops_ref_acquire_dup_ref__destroy(skel);
+}
+
+void test_struct_ops_ref_acquire(void)
+{
+ if (test__start_subtest("ref_acquire"))
+ ref_acquire();
+ if (test__start_subtest("ref_acquire_ref_leak"))
+ ref_acquire_ref_leak();
+ if (test__start_subtest("ref_acquire_dup_ref"))
+ ref_acquire_dup_ref();
+}
+
diff --git a/tools/testing/selftests/bpf/progs/struct_ops_ref_acquire.c b/tools/testing/selftests/bpf/progs/struct_ops_ref_acquire.c
new file mode 100644
index 000000000000..bae342db0fdb
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/struct_ops_ref_acquire.c
@@ -0,0 +1,27 @@
+#include <vmlinux.h>
+#include <bpf/bpf_tracing.h>
+#include "../bpf_testmod/bpf_testmod.h"
+
+char _license[] SEC("license") = "GPL";
+
+void bpf_task_release(struct task_struct *p) __ksym;
+
+/* This is a test BPF program that uses struct_ops to access a referenced
+ * kptr argument. This is a test for the verifier to ensure that it recongnizes
+ * the task as a referenced object (i.e., ref_obj_id > 0).
+ */
+SEC("struct_ops/test_ref_acquire")
+int BPF_PROG(test_ref_acquire, int dummy,
+ struct task_struct *task)
+{
+ bpf_task_release(task);
+
+ return 0;
+}
+
+SEC(".struct_ops.link")
+struct bpf_testmod_ops testmod_ref_acquire = {
+ .test_ref_acquire = (void *)test_ref_acquire,
+};
+
+
diff --git a/tools/testing/selftests/bpf/progs/struct_ops_ref_acquire_dup_ref.c b/tools/testing/selftests/bpf/progs/struct_ops_ref_acquire_dup_ref.c
new file mode 100644
index 000000000000..489db98a47fb
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/struct_ops_ref_acquire_dup_ref.c
@@ -0,0 +1,24 @@
+#include <vmlinux.h>
+#include <bpf/bpf_tracing.h>
+#include "../bpf_testmod/bpf_testmod.h"
+
+char _license[] SEC("license") = "GPL";
+
+void bpf_task_release(struct task_struct *p) __ksym;
+
+SEC("struct_ops/test_ref_acquire")
+int BPF_PROG(test_ref_acquire, int dummy,
+ struct task_struct *task)
+{
+ bpf_task_release(task);
+ bpf_task_release(task);
+
+ return 0;
+}
+
+SEC(".struct_ops.link")
+struct bpf_testmod_ops testmod_ref_acquire = {
+ .test_ref_acquire = (void *)test_ref_acquire,
+};
+
+
diff --git a/tools/testing/selftests/bpf/progs/struct_ops_ref_acquire_ref_leak.c b/tools/testing/selftests/bpf/progs/struct_ops_ref_acquire_ref_leak.c
new file mode 100644
index 000000000000..c5b9a1d748a1
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/struct_ops_ref_acquire_ref_leak.c
@@ -0,0 +1,19 @@
+#include <vmlinux.h>
+#include <bpf/bpf_tracing.h>
+#include "../bpf_testmod/bpf_testmod.h"
+
+char _license[] SEC("license") = "GPL";
+
+SEC("struct_ops/test_ref_acquire")
+int BPF_PROG(test_ref_acquire, int dummy,
+ struct task_struct *task)
+{
+ return 0;
+}
+
+SEC(".struct_ops.link")
+struct bpf_testmod_ops testmod_ref_acquire = {
+ .test_ref_acquire = (void *)test_ref_acquire,
+};
+
+
--
2.20.1
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