linux-kernel - Re: [patch 1/4] fs, proc: Introduce /proc/<pid>/task/<tid>/children entry v8

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Message-ID: <20120124065338.GB29735@moon>
Date:	Tue, 24 Jan 2012 10:53:38 +0400
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Pavel Emelyanov <xemul@...allels.com>,
	Serge Hallyn <serge.hallyn@...onical.com>,
	Kees Cook <keescook@...omium.org>, Tejun Heo <tj@...nel.org>,
	Andrew Vagin <avagin@...nvz.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Alexey Dobriyan <adobriyan@...il.com>
Subject: Re: [patch 1/4] fs, proc: Introduce /proc/<pid>/task/<tid>/children
 entry v8

On Tue, Jan 24, 2012 at 11:07:30AM +0900, KAMEZAWA Hiroyuki wrote:
...
> 
> From viewpoint I played with seq_file, yesterday.
> 
> > +static void *children_seq_start(struct seq_file *seq, loff_t *pos)
> > +{
> > +	return get_children_pid(seq->private, NULL, *pos);
> > +}
> > +
> > +static void *children_seq_next(struct seq_file *seq, void *v, loff_t *pos)
> > +{
> > +	struct pid *pid = NULL;
> > +
> > +	pid = get_children_pid(seq->private, v, *pos + 1);
> > +	if (!pid)
> > +		seq_printf(seq, "\n");
> > +	put_pid(v);
> 
> Because seq_printf() may fail. This seems dangeorus.
> 
> If seq_printf() fails and returns NULL, "\n" will not be
> printed out and user land parser will go wrong.
>

Hmm. But userspace app will get eof, so frankly I don't see
a problem here. Or maybe I miss something?

> I think all seq_printf() should be handled in ->show().
> (And you can use seq_putc() for "\n".)
> 

Sure, i'll change it to seq_putc.

	Cyrill
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