Re: siginfo pid not populated from ptrace?

Eric W. Biederman
2018-11-12T18:30:34Z

Tycho Andersen <tycho@tycho.ws> writes:

> Hi Oleg,
>
> I've been running some tests on my seccomp series, and in one of the
> tests on v4.20-rc2, I noticed,
>
> [ RUN ] global.syscall_restart
> seccomp_bpf.c:2784:global.syscall_restart:Expected getpid() (1492) == info._sifields._kill.si_pid (0)
> global.syscall_restart: Test failed at step #22
>
> which seems unrelated to my series (the kernel was stock v4.20 with my
> patches on top).
>
> I've been running a lot of tests, and only seen this once, so it seems
> like a fairly rare race. I tried to look through the code but didn't
> see anything obvious. Thoughts?

My guess would be pid namespaces, or stopping for a signal other than
SIGSTOP.

If you can get this to reproduce at all it would be interesting to see
si_signo and si_code. So that we can see just which signal is in info,
and how it should be decoded.

I see this test at line 2736 in 4.20-rc1 so there are almost 50 lines of
change in your version of seccomp_bpf.c. So I hope I am reading the
proper test.

Eric