On Sat, Jan 26, 2019 at 3:55 AM Colin King <colin.king@xxxxxxxxxxxxx> wrote:
>
> From: Colin Ian King <colin.king@xxxxxxxxxxxxx>
>
> The error return being placed in regs.SYSCALL_RET is currently positive and
> this is causing test failures on s390x. The return value should be -EPERM
> rather than EPERM otherwise a failure is not detected and errno is not set
> accordingly on s390x.
Ah, hm, interesting. Yes, the selftest was accidentally encoding the
wrong details. However, I think the test for the result is a bit more
broken. EPERM is 1, so there isn't even a sanity check that the result
is getting passed down (the -1 from syscall won't tell us if the errno
actually landed too, so we need to check that with something that
isn't EPERM).
Let me send a patch to test on s390...
-Kees
>
> Fixes: a33b2d0359a0 ("selftests/seccomp: Add tests for basic ptrace actions")
> Signed-off-by: Colin Ian King <colin.king@xxxxxxxxxxxxx>
> ---
>
> V2: remove misplaced Content-Type and Content-Transfer-Encoding fields
>
> ---
> tools/testing/selftests/seccomp/seccomp_bpf.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c b/tools/testing/selftests/seccomp/seccomp_bpf.c
> index 496a9a8c773a..957344884360 100644
> --- a/tools/testing/selftests/seccomp/seccomp_bpf.c
> +++ b/tools/testing/selftests/seccomp/seccomp_bpf.c
> @@ -1706,7 +1706,7 @@ void change_syscall(struct __test_metadata *_metadata,
> #ifdef SYSCALL_NUM_RET_SHARE_REG
> TH_LOG("Can't modify syscall return on this architecture");
> #else
> - regs.SYSCALL_RET = EPERM;
> + regs.SYSCALL_RET = -EPERM;
> #endif
>
> #ifdef HAVE_GETREGS
> @@ -1850,7 +1850,7 @@ TEST_F(TRACE_syscall, ptrace_syscall_dropped)
> true);
>
> /* Tracer should skip the open syscall, resulting in EPERM. */
> - EXPECT_SYSCALL_RETURN(EPERM, syscall(__NR_openat));
> + EXPECT_SYSCALL_RETURN(-EPERM, syscall(__NR_openat));
> }
>
> TEST_F(TRACE_syscall, syscall_allowed)
> @@ -1894,7 +1894,7 @@ TEST_F(TRACE_syscall, syscall_dropped)
> ASSERT_EQ(0, ret);
>
> /* gettid has been skipped and an altered return value stored. */
> - EXPECT_SYSCALL_RETURN(EPERM, syscall(__NR_gettid));
> + EXPECT_SYSCALL_RETURN(-EPERM, syscall(__NR_gettid));
> EXPECT_NE(self->mytid, syscall(__NR_gettid));
> }
>
> --
> 2.19.1
>
--
Kees Cook
