selftests/harness: Fix vfork() side effects

Setting the time namespace with CLONE_NEWTIME returns -EUSERS if the
calling thread shares memory with another thread (because of the shared
vDSO), which is the case when it is created with vfork().

Fix pidfd_setns_test by replacing test harness's vfork() call with a
clone3() call with CLONE_VFORK, and an explicit sharing of the
_metadata and self objects.

Replace _metadata->teardown_parent with a new FIXTURE_TEARDOWN_PARENT()
helper that can replace FIXTURE_TEARDOWN().  This is a cleaner approach
and it enables to selectively share the fixture data between the child
process running tests and the parent process running the fixture
teardown.  This also avoids updating several tests to not rely on the
self object's copy-on-write property (e.g. storing the returned value of
a fork() call).

Cc: Christian Brauner <[email protected]>
Cc: David S. Miller <[email protected]>
Cc: Günther Noack <[email protected]>
Cc: Jakub Kicinski <[email protected]>
Cc: Mark Brown <[email protected]>
Cc: Shuah Khan <[email protected]>
Cc: Will Drewry <[email protected]>
Reported-by: kernel test robot <[email protected]>
Closes: https://lore.kernel.org/oe-lkp/[email protected]
Fixes: 0710a1a73fb4 ("selftests/harness: Merge TEST_F_FORK() into TEST_F()")
Reviewed-by: Kees Cook <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Mickaël Salaün <[email protected]>

0 files changed, 0 insertions, 0 deletions