linux-kernel - Re: [PATCH 01/17] signal: Make SIGKILL during coredumps an explicit special case

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Date: Wed, 19 Jun 2024 17:50:17 +0200
From: Oleg Nesterov <oleg@...hat.com>
To: "Eric W. Biederman" <ebiederm@...ssion.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, Tejun Heo <tj@...nel.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 01/17] signal: Make SIGKILL during coredumps an explicit
 special case

Hi Eric,

I'll _try_ to read this (nontrivial) changes this week. To be honest,
right now I don't really understand your goals after the quick glance...

So far I have only looked at this simple 1/17 and it doesn't look right
to me.

On 06/18, Eric W. Biederman wrote:
>
> --- a/kernel/signal.c
> +++ b/kernel/signal.c
> @@ -907,8 +907,12 @@ static bool prepare_signal(int sig, struct task_struct *p, bool force)
>  	sigset_t flush;
>  
>  	if (signal->flags & SIGNAL_GROUP_EXIT) {
> -		if (signal->core_state)
> -			return sig == SIGKILL;
> +		if (signal->core_state && (sig == SIGKILL)) {
> +			struct task_struct *dumper =
> +				signal->core_state->dumper.task;
> +			sigaddset(&dumper->pending.signal, SIGKILL);
> +			signal_wake_up(dumper, 1);
> +		}

and after that it returns false so __send_signal_locked/send_sigqueue simply
return. This means:

	- the caller will wrongly report TRACE_SIGNAL_IGNORED

	- complete_signal() won't be called, so signal->group_exit_code
	  won't be updated.

	  coredump_finish() won't change it too so the process will exit
	  with group_exit_code == signr /* coredumping signal */.

	  Yes, the fix is obvious and trivial...

Oleg.