[PATCH] kselftest/runner: avoid using timeout when timeout is disabled

[PATCH] kselftest/runner: avoid using timeout when timeout is disabled

[Andrea Righi]

Avoid using /usr/bin/timeout unnecessarily if timeout is set to 0
(disabled) in the "settings" file for a specific test.

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.

Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
---
 tools/testing/selftests/kselftest/runner.sh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/kselftest/runner.sh b/tools/testing/selftests/kselftest/runner.sh
index e84d901f8567..2cd3c8def0f6 100644
--- a/tools/testing/selftests/kselftest/runner.sh
+++ b/tools/testing/selftests/kselftest/runner.sh
@@ -32,7 +32,7 @@ tap_prefix()
 tap_timeout()
 {
 	# Make sure tests will time out if utility is available.
-	if [ -x /usr/bin/timeout ] ; then
+	if [ -x /usr/bin/timeout ] && [ $kselftest_timeout -gt 0 ] ; then
 		/usr/bin/timeout "$kselftest_timeout" "$1"
 	else
 		"$1"
-- 
2.25.1

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

[Kees Cook]

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...

-Kees

> Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
> ---
>  tools/testing/selftests/kselftest/runner.sh | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/kselftest/runner.sh b/tools/testing/selftests/kselftest/runner.sh
> index e84d901f8567..2cd3c8def0f6 100644
> --- a/tools/testing/selftests/kselftest/runner.sh
> +++ b/tools/testing/selftests/kselftest/runner.sh
> @@ -32,7 +32,7 @@ tap_prefix()
>  tap_timeout()
>  {
>  	# Make sure tests will time out if utility is available.
> -	if [ -x /usr/bin/timeout ] ; then
> +	if [ -x /usr/bin/timeout ] && [ $kselftest_timeout -gt 0 ] ; then
>  		/usr/bin/timeout "$kselftest_timeout" "$1"
>  	else
>  		"$1"
> -- 
> 2.25.1
> 

-- 
Kees Cook

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

[Andrea Righi]

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

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

[Andrea Righi]

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...
> 
> -Kees

Hi Kees,

a quick update on this.

After further investigation Cascardo (added in cc) found that the
culprit of this issue was the usage of nanosleep() vs clock_nanosleep()
in glibc. He already sent a fix for this:

https://lkml.org/lkml/2020/4/8/968

Without this we are getting the following error:

 seccomp_bpf.c:2839:global.syscall_restart:Expected true (1) == WIFSTOPPED(status) (0)
 # global.syscall_restart: Test terminated by assertion

I still think my timeout optimization patch can be useful, but for this
particular problem we should definitely apply Cascardo's fix.

Thanks,
-Andrea

> 
> > Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
> > ---
> >  tools/testing/selftests/kselftest/runner.sh | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/tools/testing/selftests/kselftest/runner.sh b/tools/testing/selftests/kselftest/runner.sh
> > index e84d901f8567..2cd3c8def0f6 100644
> > --- a/tools/testing/selftests/kselftest/runner.sh
> > +++ b/tools/testing/selftests/kselftest/runner.sh
> > @@ -32,7 +32,7 @@ tap_prefix()
> >  tap_timeout()
> >  {
> >  	# Make sure tests will time out if utility is available.
> > -	if [ -x /usr/bin/timeout ] ; then
> > +	if [ -x /usr/bin/timeout ] && [ $kselftest_timeout -gt 0 ] ; then
> >  		/usr/bin/timeout "$kselftest_timeout" "$1"
> >  	else
> >  		"$1"
> > -- 
> > 2.25.1
> > 
> 
> -- 
> Kees Cook