linux-kernel - Re: [PATCH 04/15] task_diag: add a new interface to get information about tasks (v4)

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Date:	Tue, 12 Apr 2016 17:39:14 -0700
From:	Andrew Vagin <avagin@...il.com>
To:	Cyrill Gorcunov <gorcunov@...il.com>
Cc:	Andrey Vagin <avagin@...nvz.org>, linux-kernel@...r.kernel.org,
	Oleg Nesterov <oleg@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Pavel Emelyanov <xemul@...allels.com>,
	Roger Luethi <rl@...lgate.ch>, Arnd Bergmann <arnd@...db.de>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	David Ahern <dsahern@...il.com>,
	Andy Lutomirski <luto@...capital.net>,
	Pavel Odintsov <pavel.odintsov@...il.com>
Subject: Re: [PATCH 04/15] task_diag: add a new interface to get information
 about tasks (v4)

On Tue, Apr 12, 2016 at 10:08:57AM +0300, Cyrill Gorcunov wrote:
> On Mon, Apr 11, 2016 at 04:35:44PM -0700, Andrey Vagin wrote:
> ...
> > +static int __taskdiag_dumpit(struct task_iter *iter,
> > +			     struct task_diag_cb *cb, struct task_struct **start)
> > +{
> > +	struct user_namespace *userns = current_user_ns();
> > +	struct task_struct *task = *start;
> > +	int rc;
> > +
> > +	for (; task; task = iter_next(iter)) {
> > +		if (!ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS))
> > +			continue;
> > +
> > +		rc = task_diag_fill(task, cb->resp, &iter->req,
> > +				cb, iter->ns, userns);
> > +		if (rc < 0) {
> > +			if (rc != -EMSGSIZE)
> > +				return rc;
> > +			break;

task isn't NULL here

> > +		}
> > +	}
> > +	*start = task;
> 
> task = NULL always here?

No, it isn't if the loop is interrupted by break.

Thanks,
Andrew