Unverified Commit b55eb6eb authored by Mike Yuan's avatar Mike Yuan Committed by Christian Brauner
Browse files

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: cdda1f26 ("pidfd: add ioctl to retrieve pid info")
Signed-off-by: default avatarMike 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: default avatarChristian Brauner <brauner@kernel.org>
parent 5abc7438

fs/pidfs.c

+1 −1
Original line number Diff line number Diff line
@@ -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;



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