selftests: add pid namespace ENOMEM regression test

We recently regressed (cf. [1] and its corresponding fix in [2]) returning
ENOMEM when trying to create a process in a pid namespace whose init
process/child subreaper has already died. This has caused confusion at
least once before that (cf. [3]). Let's add a simple regression test to
catch this in the future.

[1]: 49cb2fc42ce4 ("fork: extend clone3() to support setting a PID")
[2]: b26ebfe12f34 ("pid: Fix error return value in some cases")
[3]: 35f71bc0a09a ("fork: report pid reservation failure properly")
Cc: Corey Minyard <[email protected]>
Cc: Oleg Nesterov <[email protected]>
Cc: Adrian Reber <[email protected]>
Cc: Dmitry Safonov <[email protected]>
Cc: Andrei Vagin <[email protected]>
Signed-off-by: Christian Brauner <[email protected]>

0 files changed, 0 insertions, 0 deletions