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

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Message-ID: <20120810172524.GH5416@redhat.com>
Date:	Fri, 10 Aug 2012 13:25:24 -0400
From:	Vivek Goyal <vgoyal@...hat.com>
To:	Herton Ronaldo Krzesinski <herton.krzesinski@...onical.com>
Cc:	Jiri Kosina <jkosina@...e.cz>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jens Axboe <axboe@...nel.dk>, Tejun Heo <tj@...nel.org>,
	linux-kernel@...r.kernel.org, Ben Hutchings <ben@...adent.org.uk>
Subject: Re: [PATCH 3/6] floppy: avoid leaking extra reference to queue on
 do_floppy_init error handling

On Thu, Aug 09, 2012 at 04:59:48PM -0300, Herton Ronaldo Krzesinski wrote:
> After commit 3f9a5aa ("floppy: Cleanup disk->queue before caling
> put_disk() if add_disk() was never called"), if something fails in the
> add_disk loop, we unconditionally set disks[dr]->queue to NULL. But
> that's wrong, since we may have succesfully done an add_disk on some of
> the drives previously in the loop, and in this case we would end up with
> an extra reference to the disks[dr]->queue.
> 
> Add a new global array to mark "registered" disks, and use that to check
> if we did an add_disk on one of the disks already. Using an array to
> track added disks also will help to simplify/cleanup code later, as
> suggested by Vivek Goyal.
> 
> Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski@...onical.com>
> Cc: stable@...r.kernel.org

Looks good to me.

Acked-by: Vivek Goyal <vgoyal@...hat.com>

Vivek

> ---
>  drivers/block/floppy.c |    5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/block/floppy.c b/drivers/block/floppy.c
> index 1e09e99..9272203 100644
> --- a/drivers/block/floppy.c
> +++ b/drivers/block/floppy.c
> @@ -409,6 +409,7 @@ static struct floppy_drive_struct drive_state[N_DRIVE];
>  static struct floppy_write_errors write_errors[N_DRIVE];
>  static struct timer_list motor_off_timer[N_DRIVE];
>  static struct gendisk *disks[N_DRIVE];
> +static bool disk_registered[N_DRIVE];
>  static struct block_device *opened_bdev[N_DRIVE];
>  static DEFINE_MUTEX(open_lock);
>  static struct floppy_raw_cmd *raw_cmd, default_raw_cmd;
> @@ -4305,6 +4306,7 @@ static int __init do_floppy_init(void)
>  		disks[drive]->flags |= GENHD_FL_REMOVABLE;
>  		disks[drive]->driverfs_dev = &floppy_device[drive].dev;
>  		add_disk(disks[drive]);
> +		disk_registered[drive] = true;
>  	}
>  
>  	return 0;
> @@ -4328,7 +4330,8 @@ out_put_disk:
>  			 * put_disk() is not paired with add_disk() and
>  			 * will put queue reference one extra time. fix it.
>  			 */
> -			disks[dr]->queue = NULL;
> +			if (!disk_registered[dr])
> +				disks[dr]->queue = NULL;
>  		}
>  		put_disk(disks[dr]);
>  	}
> -- 
> 1.7.9.5
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