[PATCH stable linux-5.15.y 09/10] bpf/selftests: Test PTR_TO_RDONLY_MEM

Hao Luo
2022-04-28T23:59:38Z

commit 9497c458c10b049438ef6e6ddda898edbc3ec6a8 upstream.

This test verifies that a ksym of non-struct can not be directly
updated.

Signed-off-by: Hao Luo <haoluo@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20211217003152.48334-10-haoluo@google.com
Cc: stable@vger.kernel.org # 5.15.x
---
.../selftests/bpf/prog_tests/ksyms_btf.c | 14 +++++++++
.../bpf/progs/test_ksyms_btf_write_check.c | 29 +++++++++++++++++++
2 files changed, 43 insertions(+)
create mode 100644 tools/testing/selftests/bpf/progs/test_ksyms_btf_write_check.c

diff --git a/tools/testing/selftests/bpf/prog_tests/ksyms_btf.c b/tools/testing/selftests/bpf/prog_tests/ksyms_btf.c
index cf3acfa5a91d..69455fe90ac3 100644
--- a/tools/testing/selftests/bpf/prog_tests/ksyms_btf.c
+++ b/tools/testing/selftests/bpf/prog_tests/ksyms_btf.c
@@ -7,6 +7,7 @@
#include "test_ksyms_btf.skel.h"
#include "test_ksyms_btf_null_check.skel.h"
#include "test_ksyms_weak.skel.h"
+#include "test_ksyms_btf_write_check.skel.h"

static int duration;

@@ -109,6 +110,16 @@ static void test_weak_syms(void)
test_ksyms_weak__destroy(skel);
}

+static void test_write_check(void)
+{
+ struct test_ksyms_btf_write_check *skel;
+
+ skel = test_ksyms_btf_write_check__open_and_load();
+ ASSERT_ERR_PTR(skel, "unexpected load of a prog writing to ksym memory\n");
+
+ test_ksyms_btf_write_check__destroy(skel);
+}
+
void test_ksyms_btf(void)
{
int percpu_datasec;
@@ -136,4 +147,7 @@ void test_ksyms_btf(void)

if (test__start_subtest("weak_ksyms"))
test_weak_syms();
+
+ if (test__start_subtest("write_check"))
+ test_write_check();
}
diff --git a/tools/testing/selftests/bpf/progs/test_ksyms_btf_write_check.c b/tools/testing/selftests/bpf/progs/test_ksyms_btf_write_check.c
new file mode 100644
index 000000000000..2180c41cd890
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_ksyms_btf_write_check.c
@@ -0,0 +1,29 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Google */
+
+#include "vmlinux.h"
+
+#include <bpf/bpf_helpers.h>
+
+extern const int bpf_prog_active __ksym; /* int type global var. */
+
+SEC("raw_tp/sys_enter")
+int handler(const void *ctx)
+{
+ int *active;
+ __u32 cpu;
+
+ cpu = bpf_get_smp_processor_id();
+ active = (int *)bpf_per_cpu_ptr(&bpf_prog_active, cpu);
+ if (active) {
+ /* Kernel memory obtained from bpf_{per,this}_cpu_ptr
+ * is read-only, should _not_ pass verification.
+ */
+ /* WRITE_ONCE */
+ *(volatile int *)active = -1;
+ }
+
+ return 0;
+}
+
+char _license[] SEC("license") = "GPL";
--
2.36.0.464.gb9c8b46e94-goog