linux-kernel - Re: [PATCH] block: initialize hd_stuct's reference before assigning it

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Date:	Fri, 6 May 2016 12:26:22 +0200
From:	Johannes Thumshirn <jthmshirn@...e.de>
To:	Jens Axboe <axboe@...com>
Cc:	linux-block@...r.kernel.org,
	Linux Kernel Mailinglist <linux-kernel@...r.kernel.org>,
	Hannes Reinecke <hare@...e.de>, Alexander Graf <agraf@...e.de>,
	Johannes Thumshirn <jthmshirn@...e.de>
Subject: Re: [PATCH] block: initialize hd_stuct's reference before assigning
 it

On Tue, May 03, 2016 at 03:38:03PM +0200, Johannes Thumshirn wrote:
> Inititialize the hd_struct's perpcu reference before assigning the hd_struct
> to the partition table list.
> 
> This fixes a race which could be triggered using a simple partition
> creation/deletion loop with virtio-blk on aarch64.
> 
> Signed-off-by: Johannes Thumshirn <jthumshirn@...e.de>
> ---
>  block/partition-generic.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/block/partition-generic.c b/block/partition-generic.c
> index 5d87019..aa5b83a 100644
> --- a/block/partition-generic.c
> +++ b/block/partition-generic.c
> @@ -361,6 +361,10 @@ struct hd_struct *add_partition(struct gendisk *disk, int partno,
>  			goto out_del;
>  	}
>  
> +	err = -ENOMEM;
> +	if (hd_ref_init(p))
> +		goto out_free_info;
> +
>  	/* everything is up and running, commence */
>  	rcu_assign_pointer(ptbl->part[partno], p);
>  
> @@ -368,8 +372,7 @@ struct hd_struct *add_partition(struct gendisk *disk, int partno,
>  	if (!dev_get_uevent_suppress(ddev))
>  		kobject_uevent(&pdev->kobj, KOBJ_ADD);
>  
> -	if (!hd_ref_init(p))
> -		return p;
> +	return p;
>  
>  out_free_info:
>  	free_part_info(p);
> -- 
> 1.8.5.2
> 

We've just seen that this is already fixed with b30a337ca 'block: partition:
initialize percpuref before sending out KOBJ_ADD'

Sorry for the noise,
	Johannes
-- 
Johannes Thumshirn                                          Storage
jthumshirn@...e.de                                +49 911 74053 689
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
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