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

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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>
This commit is contained in:
Oleg Nesterov 2025-03-24 18:19:41 +01:00 committed by Christian Brauner
parent 1243045c94
commit 9133607de3
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1 changed files with 3 additions and 0 deletions
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kernel/exit.c
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@ -268,6 +268,9 @@ void release_task(struct task_struct *p)
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,