linux-kernel - Re: [PATCH] wait_task_stopped: pass correct exit_code to wait_noreap

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Date:	Tue, 20 Nov 2007 07:55:22 +0000
From:	Scott James Remnant <scott@...ntu.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org, Oleg Nesterov <oleg@...sign.ru>,
	Roland McGrath <roland@...hat.com>
Subject: Re: [PATCH] wait_task_stopped: pass correct exit_code to
	wait_noreap_copyout

On Mon, 2007-11-19 at 22:43 -0800, Andrew Morton wrote:
> On Sun, 18 Nov 2007 09:13:24 +0000 Scott James Remnant <scott@...ntu.com> wrote:
> 
> > In wait_task_stopped() exit_code already contains the right value for
> > the si_status member of siginfo, and this is simply set in the non
> > WNOWAIT case.
> >     
> > Pass it unchanged to wait_noreap_copyout();  we would only need to
> > shift it and add 0x7f if we were returning it in the user status field
> > and that isn't used for any function that permits WNOWAIT.
> >     
> Is this bug visible to userspace?  If so, I'm surprised that none of the
> various testsuites (which like to exercise this sort of interface) has
> detected it.
> 
Absolutely;  if you call waitid() with a stopped or traced process,
you'll get the signal in siginfo.si_status as expected -- however if you
call waitid(WNOWAIT) at the same time, you'll get the signal << 8 | 0x7f

Scott
-- 
Scott James Remnant
scott@...ntu.com

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