Re: [PATCH net-next 1/2] connector/cn_proc: Handle threads for proc connector

From: Oleg Nesterov
Date: Fri Sep 20 2024 - 07:00:59 EST


On 09/19, Anjali Kulkarni wrote:
>
> @@ -413,6 +416,10 @@ static void cn_proc_mcast_ctl(struct cn_msg *msg,
> if (msg->len == sizeof(*pinput)) {
> pinput = (struct proc_input *)msg->data;
> mc_op = pinput->mcast_op;
> + if (mc_op == PROC_CN_MCAST_NOTIFY) {
> + current->exit_code = pinput->uexit_code;
> + return;

...

> --- a/kernel/exit.c
> +++ b/kernel/exit.c
> @@ -821,6 +821,7 @@ void __noreturn do_exit(long code)
> {
> struct task_struct *tsk = current;
> int group_dead;
> + __u32 uexit_code;
>
> WARN_ON(irqs_disabled());
>
> @@ -863,6 +864,8 @@ void __noreturn do_exit(long code)
> tty_audit_exit();
> audit_free(tsk);
>
> + uexit_code = tsk->exit_code;

I don't think you can use task_struct->exit_code. If this task is ptraced,
it can be changed/cleared in, say, ptrace_stop() after PROC_CN_MCAST_NOTIFY.

Oleg.