selftests/bpf: Test passing rdonly mem to global func

Add two test cases, one pass read only map value pointer to global
func, which should be rejected. The same code checks it for kfunc, so
that is covered as well. Second one tries to use the missing check for
PTR_TO_MEM's MEM_RDONLY flag and tries to write to a read only memory
pointer. Without prior patches, both of these tests fail.

Reviewed-by: Hao Luo <haoluo@google.com>
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20220319080827.73251-5-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

4 files changed, 46 insertions, 6 deletions

diff --git a/tools/testing/selftests/bpf/prog_tests/ksyms_btf.c b/tools/testing/selftests/bpf/prog_tests/ksyms_btf.c
index f6933b06daf8..1d7a2f1e0731 100644
--- a/tools/testing/selftests/bpf/prog_tests/ksyms_btf.c
+++ b/tools/testing/selftests/bpf/prog_tests/ksyms_btf.c
@@ -138,12 +138,16 @@ cleanup:
 	test_ksyms_weak_lskel__destroy(skel);
 }
 
-static void test_write_check(void)
+static void test_write_check(bool test_handler1)
 {
 	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");
+	skel = test_ksyms_btf_write_check__open();
+	if (!ASSERT_OK_PTR(skel, "test_ksyms_btf_write_check__open"))
+		return;
+	bpf_program__set_autoload(test_handler1 ? skel->progs.handler2 : skel->progs.handler1, false);
+	ASSERT_ERR(test_ksyms_btf_write_check__load(skel),
+		   "unexpected load of a prog writing to ksym memory\n");
 
 	test_ksyms_btf_write_check__destroy(skel);
 }
@@ -179,6 +183,9 @@ void test_ksyms_btf(void)
 	if (test__start_subtest("weak_ksyms_lskel"))
 		test_weak_syms_lskel();
 
-	if (test__start_subtest("write_check"))
-		test_write_check();
+	if (test__start_subtest("write_check1"))
+		test_write_check(true);
+
+	if (test__start_subtest("write_check2"))
+		test_write_check(false);
 }
diff --git a/tools/testing/selftests/bpf/prog_tests/test_global_funcs.c b/tools/testing/selftests/bpf/prog_tests/test_global_funcs.c
index 509e21d5cb9d..b90ee47d3111 100644
--- a/tools/testing/selftests/bpf/prog_tests/test_global_funcs.c
+++ b/tools/testing/selftests/bpf/prog_tests/test_global_funcs.c
@@ -81,6 +81,7 @@ void test_test_global_funcs(void)
 		{ "test_global_func14.o", "reference type('FWD S') size cannot be determined" },
 		{ "test_global_func15.o", "At program exit the register R0 has value" },
 		{ "test_global_func16.o", "invalid indirect read from stack" },
+		{ "test_global_func17.o", "Caller passes invalid args into func#1" },
 	};
 	libbpf_print_fn_t old_print_fn = NULL;
 	int err, i, duration = 0;
diff --git a/tools/testing/selftests/bpf/progs/test_global_func17.c b/tools/testing/selftests/bpf/progs/test_global_func17.c
new file mode 100644
index 000000000000..2b8b9b8ba018
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_global_func17.c
@@ -0,0 +1,16 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <vmlinux.h>
+#include <bpf/bpf_helpers.h>
+
+__noinline int foo(int *p)
+{
+	return p ? (*p = 42) : 0;
+}
+
+const volatile int i;
+
+SEC("tc")
+int test_cls(struct __sk_buff *skb)
+{
+	return foo((int *)&i);
+}
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
index 2180c41cd890..a72a5bf3812a 100644
--- a/tools/testing/selftests/bpf/progs/test_ksyms_btf_write_check.c
+++ b/tools/testing/selftests/bpf/progs/test_ksyms_btf_write_check.c
@@ -8,7 +8,7 @@
 extern const int bpf_prog_active __ksym; /* int type global var. */
 
 SEC("raw_tp/sys_enter")
-int handler(const void *ctx)
+int handler1(const void *ctx)
 {
 	int *active;
 	__u32 cpu;
@@ -26,4 +26,20 @@ int handler(const void *ctx)
 	return 0;
 }
 
+__noinline int write_active(int *p)
+{
+	return p ? (*p = 42) : 0;
+}
+
+SEC("raw_tp/sys_enter")
+int handler2(const void *ctx)
+{
+	int *active;
+	__u32 cpu;
+
+	active = bpf_this_cpu_ptr(&bpf_prog_active);
+	write_active(active);
+	return 0;
+}
+
 char _license[] SEC("license") = "GPL";