2020-04-10 10:05:37

by Andrea Righi

Subject: [PATCH] kselftest/runner: allow to properly deliver signals to tests

While running seccomp_bpf, kill_after_ptrace() gets stuck if we run it
via /usr/bin/timeout (that is the default), until the timeout expires.

This is because /usr/bin/timeout is preventing to properly deliver
signals to ptrace'd children (SIGSYS in this case).

This problem can be easily reproduced by running:

$ sudo make TARGETS=seccomp kselftest
...

# [ RUN ] TRACE_syscall.skip_a#
not ok 1 selftests: seccomp: seccomp_bpf # TIMEOUT

The test is hanging at this point until the timeout expires and then it
reports the timeout error.

Prevent this problem by passing --foreground to /usr/bin/timeout,
allowing to properly deliver signals to children processes.

Signed-off-by: Andrea Righi <[email protected]>
---
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..676b3a8b114d 100644
--- a/tools/testing/selftests/kselftest/runner.sh
+++ b/tools/testing/selftests/kselftest/runner.sh
@@ -33,7 +33,7 @@ tap_timeout()
{
# Make sure tests will time out if utility is available.
if [ -x /usr/bin/timeout ] ; then
- /usr/bin/timeout "$kselftest_timeout" "$1"
+ /usr/bin/timeout --foreground "$kselftest_timeout" "$1"
else
"$1"
fi
--
2.25.1

2020-04-10 20:34:29

by Kees Cook

Subject: Re: [PATCH] kselftest/runner: allow to properly deliver signals to tests

On Fri, Apr 10, 2020 at 12:02:59PM +0200, Andrea Righi wrote:
> While running seccomp_bpf, kill_after_ptrace() gets stuck if we run it
> via /usr/bin/timeout (that is the default), until the timeout expires.
>
> This is because /usr/bin/timeout is preventing to properly deliver
> signals to ptrace'd children (SIGSYS in this case).
>
> This problem can be easily reproduced by running:
>
> $ sudo make TARGETS=seccomp kselftest
> ...
>
> # [ RUN ] TRACE_syscall.skip_a#
> not ok 1 selftests: seccomp: seccomp_bpf # TIMEOUT
>
> The test is hanging at this point until the timeout expires and then it
> reports the timeout error.
>
> Prevent this problem by passing --foreground to /usr/bin/timeout,
> allowing to properly deliver signals to children processes.

Interesting! This seems a poor behavior on "timeout"'s part. Is it
setting a signal mask? Hmpf. Thanks for tracking this down! This seems
like the best solution now, so:

Acked-by: Kees Cook <[email protected]>

-Kees

>
> Signed-off-by: Andrea Righi <[email protected]>
> ---
> 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..676b3a8b114d 100644
> --- a/tools/testing/selftests/kselftest/runner.sh
> +++ b/tools/testing/selftests/kselftest/runner.sh
> @@ -33,7 +33,7 @@ tap_timeout()
> {
> # Make sure tests will time out if utility is available.
> if [ -x /usr/bin/timeout ] ; then
> - /usr/bin/timeout "$kselftest_timeout" "$1"
> + /usr/bin/timeout --foreground "$kselftest_timeout" "$1"
> else
> "$1"
> fi
> --
> 2.25.1
>

--
Kees Cook