linux-kernel - Re: [PATCH v3 3/6] floppy: avoid leaking extra reference to queue on do_floppy

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Message-ID: <20120814143346.GC5277@herton-Z68MA-D2H-B3>
Date:	Tue, 14 Aug 2012 11:33:48 -0300
From:	Herton Ronaldo Krzesinski <herton.krzesinski@...onical.com>
To:	Ben Hutchings <ben@...adent.org.uk>
Cc:	Jens Axboe <axboe@...nel.dk>, Jiri Kosina <jkosina@...e.cz>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Tejun Heo <tj@...nel.org>, linux-kernel@...r.kernel.org,
	Vivek Goyal <vgoyal@...hat.com>,
	Stanislaw Gruszka <sgruszka@...hat.com>
Subject: Re: [PATCH v3 3/6] floppy: avoid leaking extra reference to queue on
 do_floppy_init error handling

On Tue, Aug 14, 2012 at 04:20:39AM +0100, Ben Hutchings wrote:
> It's totally ridiculous that a driver should have to do this.  Any
> registered disk should have the GENHD_FL_UP flag set... so why can't
> genhd check it?  It doesn't look like floppy is the only driver affected
> by this problem, either.  So I suggest the following general fix
> (untested):
> 
> ---
> Subject: genhd: Make put_disk() safe for disks that have not been registered
> 
> Since commit 9f53d2f ('block: fix __blkdev_get and add_disk race
> condition'), add_disk() adds a reference to disk->queue, which is then
> dropped by disk_release().  But if a disk is destroyed without being
> registered through add_disk() (or if add_disk() fails at the first
> hurdle) then we have a reference imbalance.
> 
> Use the GENHD_FL_UP flag to tell whether this extra reference has been
> added.  Remove the incomplete workaround from the floppy driver.

Indeed this is a more sane/right approach.

Acked-by: Herton Ronaldo Krzesinski <herton.krzesinski@...onical.com>

Just the changelog is pointing to the wrong commit as already noted by
Stanislaw.

> 
> Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
> Cc: stable@...r.kernel.org

-- 
[]'s
Herton
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