On Sat, Jul 04, 2020 at 11:12:32PM -0700, Kees Cook wrote:
> There should be no difference between -1 and other negative syscalls
> while tracing.
>
> Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
> Cc: Will Drewry <wad@xxxxxxxxxxxx>
> Cc: Will Deacon <will@xxxxxxxxxx>
> Cc: Keno Fischer <keno@xxxxxxxxxxxxxxxxxx>
> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
> ---
> tools/testing/selftests/seccomp/seccomp_bpf.c | 26 +++++++++++++++++++
> 1 file changed, 26 insertions(+)
>
> diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c b/tools/testing/selftests/seccomp/seccomp_bpf.c
> index 966dec340ea8..bf6aa06c435c 100644
> --- a/tools/testing/selftests/seccomp/seccomp_bpf.c
> +++ b/tools/testing/selftests/seccomp/seccomp_bpf.c
> @@ -1973,6 +1973,32 @@ FIXTURE_TEARDOWN(TRACE_syscall)
> teardown_trace_fixture(_metadata, self->tracer);
> }
>
> +TEST(negative_ENOSYS)
> +{
> + /* Untraced negative syscalls should return ENOSYS. */
> + errno = 0;
> + EXPECT_EQ(-1, syscall(-1));
> + EXPECT_EQ(errno, ENOSYS);
> + errno = 0;
> + EXPECT_EQ(-1, syscall(-101));
> + EXPECT_EQ(errno, ENOSYS);
> +}
> +
> +TEST_F(TRACE_syscall, negative_ENOSYS)
> +{
> + /*
> + * There should be no difference between an "internal" skip
> + * and userspace asking for syscall "-1".
> + */
> + errno = 0;
> + EXPECT_EQ(-1, syscall(-1));
> + EXPECT_EQ(errno, ENOSYS);
> + /* And no difference for "still not valid but not -1". */
> + errno = 0;
> + EXPECT_EQ(-1, syscall(-101));
> + EXPECT_EQ(errno, ENOSYS);
> +}
> +
I realized after sending this that the second function could just be:
+TEST_F(TRACE_syscall, negative_ENOSYS)
+{
+ negative_ENOSYS(_metadata);
+}
:)
> TEST_F(TRACE_syscall, syscall_allowed)
> {
> /* getppid works as expected (no changes). */
> --
> 2.25.1
>
--
Kees Cook
