linux-kernel - Re: 2.6.35-rc2 module reference counting broken

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Message-ID: <4C10CCFB.4030203@kernel.org>
Date:	Thu, 10 Jun 2010 13:31:07 +0200
From:	Tejun Heo <tj@...nel.org>
To:	Jari Ruusu <jariruusu@...rs.sourceforge.net>
CC:	Al Viro <viro@...IV.linux.org.uk>, linux-kernel@...r.kernel.org,
	Rusty Russell <rusty@...tcorp.com.au>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Nick Piggin <npiggin@...e.de>,
	Jens Axboe <jens.axboe@...cle.com>
Subject: Re: 2.6.35-rc2 module reference counting broken

Hello,

On 06/10/2010 08:34 AM, Jari Ruusu wrote:
> Later in the mount system call handling the module refrence count is
> incremented. But to me that looks like there is a window of opportunity for
> things to go wrong. What is there to prevent module from being removed at
> zero refcount?

It can be removed, in which case blkdev_get() fails and the whole open
attempt fails, which is the expected behavior.  Claiming block just
needs access to the containing struct block_device, caring for the
actual device and backing module is blkdev_get()'s job.

Thanks.

-- 
tejun
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