linux-kernel - Re: [PATCH] exit: trigger panic when init process is set to SIGNAL_GROUP

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Message-ID: <20210310173236.GB8973@redhat.com>
Date:   Wed, 10 Mar 2021 18:32:37 +0100
From:   Oleg Nesterov <oleg@...hat.com>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     qianli zhao <zhaoqianligood@...il.com>, christian@...uner.io,
        axboe@...nel.dk, Thomas Gleixner <tglx@...utronix.de>,
        Peter Collingbourne <pcc@...gle.com>,
        linux-kernel@...r.kernel.org, Qianli Zhao <zhaoqianli@...omi.com>
Subject: Re: [PATCH] exit: trigger panic when init process is set to
 SIGNAL_GROUP_EXIT

On 03/10, Eric W. Biederman wrote:
>
> 	/* If global init has exited,
>          * panic immediately to get a useable coredump.
>          */
> 	if (unlikely(is_global_init(tsk) &&
> 	    (thread_group_empty(tsk) ||
>             (tsk->signal->flags & SIGNAL_GROUP_EXIT)))) {
> 		panic("Attempted to kill init!	exitcode=0x%08x\n",
>                 	tsk->signal->group_exit_code ?: (int)code);
> 	}
>
> The thread_group_empty test is needed to handle single threaded
> inits.

But we can't rely on thread_group_empty(). Just suppose that the main
thread exit first, then the 2nd (last) thread exits too.

Oleg.