From: Hao Luo <haoluo@google.com>
Date: Thu, 16 Dec 2021 16:31:52 -0800
Subject: bpf/selftests: Test PTR_TO_RDONLY_MEM
Patch-mainline: v5.17-rc1
Git-commit: 9497c458c10b049438ef6e6ddda898edbc3ec6a8
References: bsc#1196261 CVE-2022-0500
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
Acked-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
---
tools/testing/selftests/bpf/prog_tests/ksyms_btf.c | 14 ++++
tools/testing/selftests/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
--- a/tools/testing/selftests/bpf/prog_tests/ksyms_btf.c
+++ b/tools/testing/selftests/bpf/prog_tests/ksyms_btf.c
@@ -6,6 +6,7 @@
#include <bpf/btf.h>
#include "test_ksyms_btf.skel.h"
#include "test_ksyms_btf_null_check.skel.h"
+#include "test_ksyms_btf_write_check.skel.h"
static int duration;
@@ -81,6 +82,16 @@ static void test_null_check(void)
test_ksyms_btf_null_check__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;
@@ -105,4 +116,7 @@ void test_ksyms_btf(void)
if (test__start_subtest("null_check"))
test_null_check();
+
+ if (test__start_subtest("write_check"))
+ test_write_check();
}
--- /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";