pidfs: never refuse ppid == 0 in PIDFD_GET_INFO

In systemd we spotted an issue after switching to ioctl(PIDFD_GET_INFO)
for obtaining pid number the pidfd refers to, that for processes
with a parent from outer pidns PIDFD_GET_INFO unexpectedly yields
-ESRCH [1]. It turned out that there's an arbitrary check blocking
this, which is not really sensible given getppid() happily returns
0 for such processes. Just drop the spurious check and userspace
ought to handle ppid == 0 properly everywhere.

[1] https://github.com/systemd/systemd/issues/37715

Fixes: cdda1f26e74b ("pidfd: add ioctl to retrieve pid info")
Signed-off-by: Mike Yuan <[email protected]>
Link: https://lore.kernel.org/[email protected]
Cc: Christian Brauner <[email protected]>
Cc: Luca Boccassi <[email protected]>
Cc: [email protected]
Signed-off-by: Christian Brauner <[email protected]>

0 files changed, 0 insertions, 0 deletions