linux-kernel - Re: Yet another pipe related oops.

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Message-ID: <20130401212142.GD21522@ZenIV.linux.org.uk>
Date:	Mon, 1 Apr 2013 22:21:42 +0100
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Dave Jones <davej@...hat.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: Yet another pipe related oops.

On Mon, Apr 01, 2013 at 02:00:29PM -0700, Greg Kroah-Hartman wrote:

> > IOW, how do we deal with a race between attempt to open a debugfs file and
> > its removal on driver unload?  Greg?
> 
> Hm, I thought the i_fop->owner thing would be the needed protection, but

It will be, if you manage to fetch it...

> I guess you are right, it will not.  I guess we need to do what
> character devices do and have an "intermediate" fops in order to protect
> this.  Would that work?

You mean, with reassigning ->f_op in ->open()?  That'll work, as long as
we have exclusion between removal and fetching the sucker in primary
->open()...  Where would you prefer to stash fops?
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