[PATCH v6 00/10] Fix Kselftest's vfork() side effects

[Mickaël Salaün]

Hi,

This sixth series just update the last patch description.

Shuah, I think this should be in -next really soon to make sure
everything works fine for the v6.9 release, which is not currently the
case.  I cannot test against all kselftests though.  I would prefer to
let you handle this, but I guess you're not able to do so and I'll push
it on my branch without reply from you.  Even if I push it on my branch,
please push it on yours too as soon as you see this and I'll remove it
from mine.

Mark, Jakub, could you please test this series?

As reported by Kernel Test Robot [1] and Sean Christopherson [2], some
tests fail since v6.9-rc1 .  This is due to the use of vfork() which
introduced some side effects.  Similarly, while making it more generic,
a previous commit made some Landlock file system tests flaky, and
subject to the host's file system mount configuration.

This series fixes all these side effects by replacing vfork() with
clone3() and CLONE_VFORK, which is cleaner (no arbitrary shared memory)
and makes the Kselftest framework more robust.

I tried different approaches and I found this one to be the cleaner and
less invasive for current test cases.

I successfully ran the following tests (using TEST_F and
fork/clone/clone3, and KVM_ONE_VCPU_TEST) with this series:
- kvm:fix_hypercall_test
- kvm:sync_regs_test
- kvm:userspace_msr_exit_test
- kvm:vmx_pmu_caps_test
- landlock:fs_test
- landlock:net_test
- landlock:ptrace_test
- move_mount_set_group:move_mount_set_group_test
- net/af_unix:scm_pidfd
- perf_events:remove_on_exec
- pidfd:pidfd_getfd_test
- pidfd:pidfd_setns_test
- seccomp:seccomp_bpf
- user_events:abi_test

[1] https://lore.kernel.org/oe-lkp/202403291015.1fcfa957-oliver.sang@xxxxxxxxx
[2] https://lore.kernel.org/r/ZjPelW6-AbtYvslu@xxxxxxxxxx

Previous versions:
v1: https://lore.kernel.org/r/20240426172252.1862930-1-mic@xxxxxxxxxxx
v2: https://lore.kernel.org/r/20240429130931.2394118-1-mic@xxxxxxxxxxx
v3: https://lore.kernel.org/r/20240429191911.2552580-1-mic@xxxxxxxxxxx
v4: https://lore.kernel.org/r/20240502210926.145539-1-mic@xxxxxxxxxxx
v5: https://lore.kernel.org/r/20240503105820.300927-1-mic@xxxxxxxxxxx

Regards,

Mickaël Salaün (10):
  selftests/pidfd: Fix config for pidfd_setns_test
  selftests/landlock: Fix FS tests when run on a private mount point
  selftests/harness: Fix fixture teardown
  selftests/harness: Fix interleaved scheduling leading to race
    conditions
  selftests/landlock: Do not allocate memory in fixture data
  selftests/harness: Constify fixture variants
  selftests/pidfd: Fix wrong expectation
  selftests/harness: Share _metadata between forked processes
  selftests/harness: Fix vfork() side effects
  selftests/harness: Handle TEST_F()'s explicit exit codes

 tools/testing/selftests/kselftest_harness.h   | 122 +++++++++++++-----
 tools/testing/selftests/landlock/fs_test.c    |  83 +++++++-----
 tools/testing/selftests/pidfd/config          |   2 +
 .../selftests/pidfd/pidfd_setns_test.c        |   2 +-
 4 files changed, 143 insertions(+), 66 deletions(-)


base-commit: e67572cd2204894179d89bd7b984072f19313b03
-- 
2.45.0