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 <me@xxxxxxxxxxx> Cc: Christian Brauner <brauner@xxxxxxxxxx> Cc: Luca Boccassi <luca.boccassi@xxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> --- fs/pidfs.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/pidfs.c b/fs/pidfs.c index c1f0a067be40..69919be1c9d8 100644 --- a/fs/pidfs.c +++ b/fs/pidfs.c @@ -366,7 +366,7 @@ static long pidfd_info(struct file *file, unsigned int cmd, unsigned long arg) kinfo.pid = task_pid_vnr(task); kinfo.mask |= PIDFD_INFO_PID; - if (kinfo.pid == 0 || kinfo.tgid == 0 || (kinfo.ppid == 0 && kinfo.pid != 1)) + if (kinfo.pid == 0 || kinfo.tgid == 0) return -ESRCH; copy_out: base-commit: 5abc7438f1e9d62e91ad775cc83c9594c48d2282 -- 2.49.0
