Mike Yuan b55eb6eb2a 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: cdda1f26e7 ("pidfd: add ioctl to retrieve pid info")
Signed-off-by: Mike Yuan <me@yhndnzj.com>
Link: https://lore.kernel.org/20250604150238.42664-1-me@yhndnzj.com
Cc: Christian Brauner <brauner@kernel.org>
Cc: Luca Boccassi <luca.boccassi@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>

2025-06-04 22:48:32 +02:00

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