[PATCH bpf-next v7 04/24] selftests/bpf: add test for accessing ctx from syscall program type

Benjamin Tissoires
2022-07-21T15:38:12Z

We need to also export the kfunc set to the syscall program type,
and then add a couple of eBPF programs that are testing those calls.

The first one checks for valid access, and the second one is OK
from a static analysis point of view but fails at run time because
we are trying to access outside of the allocated memory.

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>

---

changes in v7:
- add 1 more case to ensure we can read the entire sizeof(ctx)
- add a test case for when the context is NULL

new in v6
---
net/bpf/test_run.c | 1 +
.../selftests/bpf/prog_tests/kfunc_call.c | 28 +++++++++++++++
.../selftests/bpf/progs/kfunc_call_test.c | 36 +++++++++++++++++++
3 files changed, 65 insertions(+)

diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
index dc9dc0bedca0..8ada09ab1b15 100644
--- a/net/bpf/test_run.c
+++ b/net/bpf/test_run.c
@@ -1649,6 +1649,7 @@ static int __init bpf_prog_test_run_init(void)
int ret;

ret = register_btf_kfunc_id_set(BPF_PROG_TYPE_SCHED_CLS, &bpf_prog_test_kfunc_set);
+ ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_SYSCALL, &bpf_prog_test_kfunc_set);
return ret ?: register_btf_id_dtor_kfuncs(bpf_prog_test_dtor_kfunc,
ARRAY_SIZE(bpf_prog_test_dtor_kfunc),
THIS_MODULE);
diff --git a/tools/testing/selftests/bpf/prog_tests/kfunc_call.c b/tools/testing/selftests/bpf/prog_tests/kfunc_call.c
index c00eb974eb85..7e4804cce6b9 100644
--- a/tools/testing/selftests/bpf/prog_tests/kfunc_call.c
+++ b/tools/testing/selftests/bpf/prog_tests/kfunc_call.c
@@ -6,10 +6,22 @@
#include "kfunc_call_test_subprog.skel.h"
#include "kfunc_call_test_subprog.lskel.h"

+struct syscall_test_args {
+ __u8 data[16];
+ size_t size;
+};
+
static void test_main(void)
{
struct kfunc_call_test_lskel *skel;
int prog_fd, err;
+ struct syscall_test_args args = {
+ .size = 10,
+ };
+ DECLARE_LIBBPF_OPTS(bpf_test_run_opts, syscall_topts,
+ .ctx_in = &args,
+ .ctx_size_in = sizeof(args),
+ );
LIBBPF_OPTS(bpf_test_run_opts, topts,
.data_in = &pkt_v4,
.data_size_in = sizeof(pkt_v4),
@@ -35,6 +47,22 @@ static void test_main(void)
ASSERT_OK(err, "bpf_prog_test_run(test_ref_btf_id)");
ASSERT_EQ(topts.retval, 0, "test_ref_btf_id-retval");

+ prog_fd = skel->progs.kfunc_syscall_test.prog_fd;
+ err = bpf_prog_test_run_opts(prog_fd, &syscall_topts);
+ ASSERT_OK(err, "bpf_prog_test_run(syscall_test)");
+
+ prog_fd = skel->progs.kfunc_syscall_test_fail.prog_fd;
+ err = bpf_prog_test_run_opts(prog_fd, &syscall_topts);
+ ASSERT_ERR(err, "bpf_prog_test_run(syscall_test_fail)");
+
+ syscall_topts.ctx_in = NULL;
+ syscall_topts.ctx_size_in = 0;
+
+ prog_fd = skel->progs.kfunc_syscall_test_null.prog_fd;
+ err = bpf_prog_test_run_opts(prog_fd, &syscall_topts);
+ ASSERT_OK(err, "bpf_prog_test_run(syscall_test_null)");
+ ASSERT_EQ(syscall_topts.retval, 0, "syscall_test_null-retval");
+
kfunc_call_test_lskel__destroy(skel);
}

diff --git a/tools/testing/selftests/bpf/progs/kfunc_call_test.c b/tools/testing/selftests/bpf/progs/kfunc_call_test.c
index 5aecbb9fdc68..da7ae0ef9100 100644
--- a/tools/testing/selftests/bpf/progs/kfunc_call_test.c
+++ b/tools/testing/selftests/bpf/progs/kfunc_call_test.c
@@ -92,4 +92,40 @@ int kfunc_call_test_pass(struct __sk_buff *skb)
return 0;
}

+struct syscall_test_args {
+ __u8 data[16];
+ size_t size;
+};
+
+SEC("syscall")
+int kfunc_syscall_test(struct syscall_test_args *args)
+{
+ const int size = args->size;
+
+ if (size > sizeof(args->data))
+ return -7; /* -E2BIG */
+
+ bpf_kfunc_call_test_mem_len_pass1(&args->data, sizeof(args->data));
+ bpf_kfunc_call_test_mem_len_pass1(&args->data, sizeof(*args));
+ bpf_kfunc_call_test_mem_len_pass1(&args->data, size);
+
+ return 0;
+}
+
+SEC("syscall")
+int kfunc_syscall_test_null(struct syscall_test_args *args)
+{
+ bpf_kfunc_call_test_mem_len_pass1(args, 0);
+
+ return 0;
+}
+
+SEC("syscall")
+int kfunc_syscall_test_fail(struct syscall_test_args *args)
+{
+ bpf_kfunc_call_test_mem_len_pass1(&args->data, sizeof(*args) + 1);
+
+ return 0;
+}
+
char _license[] SEC("license") = "GPL";
--
2.36.1