linux-kernel - Re: [PATCH 09/10] ptrace: add JOBCTL_BLOCK

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Message-ID: <20110519165851.GQ627@htj.dyndns.org>
Date:	Thu, 19 May 2011 18:58:51 +0200
From:	Tejun Heo <tj@...nel.org>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	jan.kratochvil@...hat.com, vda.linux@...glemail.com,
	linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, indan@....nu, bdonlan@...il.com
Subject: Re: [PATCH 09/10] ptrace: add JOBCTL_BLOCK_NOTIFY

On Thu, May 19, 2011 at 06:48:33PM +0200, Oleg Nesterov wrote:
> On 05/19, Tejun Heo wrote:
> >
> > Hello,
> >
> > On Thu, May 19, 2011 at 06:32:33PM +0200, Oleg Nesterov wrote:
> > > > +	/*
> > > > +	 * Make sure @chlid is still ptraced by us and clear BLOCK_NOTIFY.
> > > > +	 */
> > > > +	if (likely((child->ptrace & PT_PTRACED) && child->parent == current))
> > >
> > > This looks a bit confusing... It is either traced or not. If it is traced,
> > > nobody else can trace it. In fact even PT_PTRACED is not strictly needed
> > > but I agree this check makes the code cleaner.
> >
> > Hmmm... I suppose we can make the error paths finer grained so that
> > attach failure
> 
> Ah, you are right again, I forgot about PTRACE_ATTACH path.

We can move the PT_PTRACED and parenthood test outside the siglock tho
and I agree that the 'still ptraced' comment is misleading.  I'll
update it.

Thanks.

-- 
tejun
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