linux-kernel - Re: [PATCH] get_signal: simplify/cleanup the the usage of ksig->info

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Date: Mon, 26 Feb 2024 10:52:41 +0100
From: Oleg Nesterov <oleg@...hat.com>
To: Wen Yang <wenyang.linux@...mail.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Christian Brauner <brauner@...nel.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] get_signal: simplify/cleanup the the usage of ksig->info

OK, lets forget about "no need to initialize ksig->info" part for now.

Yes, PF_USER_WORKER's never dereference ksig, but I agree this doesn't
look clean without other cleanups. I'll probably return to this later
when other pending problems with PF_USER_WORKER are fixed.

Wen, thanks again for your review.

Oleg.

On 02/23, Oleg Nesterov wrote:
>
> On 02/23, Oleg Nesterov wrote:
> >
> > On 02/23, Oleg Nesterov wrote:
> > >
> > > On 02/23, Wen Yang wrote:
> > > >
> > > >
> > > > On 2024/2/23 18:50, Oleg Nesterov wrote:
> > > > >+			/*
> > > > >+			 * implies do_group_exit(), no need to initialize
> > > > >+			 * ksig->info
> > > > >+			 */
> > > > >  			goto fatal;
> > > >
> > > > There is little question:
> > > > If the this conditions is met:
> > > >    current->flags & PF_USER_WORKER
> > > > It may execute “goto out“ instead of do_group_exit().
> > >
> > > Yes, but vhost/io workers do not use ksig at all.
> >
> > Ah, wait...
> >
> > I forgot about the ->sa_flags check before hide_si_addr_tag_bits().
> >
> > OK, thanks... I'll send V2.
>
> Tomorrow.
>
> I'll recheck, but I think we need the patch below as 1/2 regadless of
> this change
>
> Oleg.
> ---
>
> --- a/kernel/signal.c
> +++ b/kernel/signal.c
> @@ -2897,13 +2897,13 @@ bool get_signal(struct ksignal *ksig)
>  		/* NOTREACHED */
>  	}
>  	spin_unlock_irq(&sighand->siglock);
> -out:
> +
>  	ksig->sig = signr;
>
>  	if (!(ksig->ka.sa.sa_flags & SA_EXPOSE_TAGBITS))
>  		hide_si_addr_tag_bits(ksig);
> -
> -	return ksig->sig > 0;
> +out:
> +	return signr > 0;
>  }
>
>  /**