On 12/19/21 5:51 PM, Alexei Starovoitov wrote:
On Thu, Dec 09, 2021 at 09:35:59AM -0800, Yonghong Song wrote:
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.
...
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;
+}
This is a targeted synthetic test. Great, but can you add one
that probes real kernel function like:
getsockname(int fd, struct sockaddr __user *usockaddr
or
getpeername(int fd, struct sockaddr __user *usockaddr > and the bpf prog tries to deref usockaddr ?
Ack. Will do.
