exit: fix the usage of delay_group_leader->exit_code in do_notify_parent() and pidfs_...

Consider a process with a group leader L and a sub-thread T.
L does sys_exit(1), then T does sys_exit_group(2).

In this case wait_task_zombie(L) will notice SIGNAL_GROUP_EXIT and use
L->signal->group_exit_code, this is correct.

But, before that, do_notify_parent(L) called by release_task(T) will use
L->exit_code != L->signal->group_exit_code, and this is not consistent.
We don't really care, I think that nobody relies on the info which comes
with SIGCHLD, if nothing else SIGCHLD < SIGRTMIN can be queued only once.

But pidfs_exit() is more problematic, I think pidfs_exit_info->exit_code
should report ->group_exit_code in this case, just like wait_task_zombie().

TODO: with this change we can hopefully cleanup (or may be even kill) the
similar SIGNAL_GROUP_EXIT checks, at least in wait_task_zombie().

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Link: https://lore.kernel.org/r/20250324171941.GA13114@redhat.com
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/kernel/exit.c b/kernel/exit.c
index 5d1226fdfadccaf136b537df0899bb0c1167057f..1b51dc099f1e05cea8185d56e80c063bad62bf21 100644 (file)
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -268,6 +268,9 @@ repeat:
        leader = p->group_leader;
        if (leader != p && thread_group_empty(leader)
                        && leader->exit_state == EXIT_ZOMBIE) {
+               /* for pidfs_exit() and do_notify_parent() */
+               if (leader->signal->flags & SIGNAL_GROUP_EXIT)
+                       leader->exit_code = leader->signal->group_exit_code;
                /*
                 * If we were the last child thread and the leader has
                 * exited already, and the leader's parent ignores SIGCHLD,