linux-kernel - Re: [PATCH v2 4/4] proc: avoid ->f_pos overflows in proc_task

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Message-ID: <20130604195700.GA31933@redhat.com>
Date:	Tue, 4 Jun 2013 21:57:00 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Al Viro <viro@...IV.linux.org.uk>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Michal Hocko <mhocko@...e.cz>,
	Sergey Dyasly <dserrg@...il.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 4/4] proc: avoid ->f_pos overflows in
	proc_task_readdir() paths

On 06/04, Al Viro wrote:
>
> On Tue, Jun 04, 2013 at 07:14:35PM +0200, Oleg Nesterov wrote:
> > > There is another bug in here as well that we may return really crazy
> > > things in the case of seek simultaneous with readdir.
> >
> > i_mutex? both vfs_readdir() and default_llseek() take it... Anyway, this
> > is another issue.
>
> That's part of the reasons for the series I've mentioned (vfs.git#experimental);
> seriously, check that up.

Will do... but so far I am confused.

I do not see how they could race (I mean /proc/pid/task only). OK, OK,
the usage of ->f_pos in sys_getdents() looks "obviously wrong", but this
is another story? And "put f_pos in a local variable" can't help.

But if you meant other problems with readdir in general, then I seem
to understand, thanks.

Oleg.

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