linux-kernel - Re: [PATCH] kselftest/runner: avoid using timeout when timeout is disabled

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Date:   Sat, 28 Mar 2020 12:31:45 +0100
From:   Andrea Righi <andrea.righi@...onical.com>
To:     Kees Cook <keescook@...omium.org>
Cc:     Shuah Khan <shuah@...nel.org>, linux-kselftest@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kselftest/runner: avoid using timeout when timeout is
 disabled

On Fri, Mar 27, 2020 at 12:28:05PM -0700, Kees Cook wrote:
> On Fri, Mar 27, 2020 at 10:36:20AM +0100, Andrea Righi wrote:
> > Avoid using /usr/bin/timeout unnecessarily if timeout is set to 0
> > (disabled) in the "settings" file for a specific test.
> 
> That seems to be a reasonable optimization, sure.
> 
> > NOTE: without this change (and adding timeout=0 in the corresponding
> > settings file - tools/testing/selftests/seccomp/settings) the
> > seccomp_bpf selftest is always failing with a timeout event during the
> > syscall_restart step.
> 
> This, however, is worrisome. I think there is something else wrong here.
> I will investigate why the output of seccomp_bpf is weird when running
> under the runner scripts. Hmmm. The output looks corrupted...

Running seccomp_bpf directly (without using runner.sh) shows this error:

 $ sudo ./tools/testing/selftests/seccomp/seccomp_bpf
 ...
 seccomp_bpf.c:2839:global.syscall_restart:Expected true (1) == WIFSTOPPED(status) (0)
 global.syscall_restart: Test terminated by assertion

Instead, running it via /usr/bin/timeout (with timeout disabled):

  $ sudo /usr/bin/timeout 0 ./tools/testing/selftests/seccomp/seccomp_bpf
  ...
  [ RUN      ] TSYNC.siblings_fail_prctl

It gets stuck here forever, basically it's during the execution of
syscall_restart().

I'll investigate more later.

Thanks,
-Andrea