linux-kernel - Re: [PATCH v1] block: partition: initialize percpuref before new partition is visiable

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Date:	Thu, 31 Mar 2016 10:15:16 +0200
From:	Johannes Thumshirn <jthumshirn@...e.de>
To:	Ming Lei <ming.lei@...onical.com>
Cc:	Jens Axboe <axboe@...com>, linux-kernel@...r.kernel.org,
	linux-block@...r.kernel.org, Christoph Hellwig <hch@...radead.org>,
	Naveen Kaje <nkaje@...eaurora.org>, stable@...r.kernel.org,
	linux-block-owner@...r.kernel.org
Subject: Re: [PATCH v1] block: partition: initialize percpuref before new
 partition is visiable

On 2016-03-31 04:40, Ming Lei wrote:
> The initialization of partition's percpu_ref should have been done 
> before
> the new partition is updated to partition table via
> rcu_assign_pointer(), otherwise the uninitialized percpu_ref may be 
> accessed
> in data path.
> 
> This patch fixes this issue reported by Naveen.
> 
> Reported-by: Naveen Kaje <nkaje@...eaurora.org>
> Tested-by: Naveen Kaje <nkaje@...eaurora.org>
> Fixes: 6c71013ecb7e2(block: partition: convert percpu ref)
> Cc: <stable@...r.kernel.org> # v4.3+
> Signed-off-by: Ming Lei <ming.lei@...onical.com>
> ---
> V1:
> 	- put 'if' around the actual device_remove_file at the label
> 	as suggested by Christoph
> 	- make commit log more accurate
> 
>  block/partition-generic.c | 11 ++++++++---
>  1 file changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/block/partition-generic.c b/block/partition-generic.c
> index 5d87019..54d4be8 100644
> --- a/block/partition-generic.c
> +++ b/block/partition-generic.c
> @@ -361,15 +361,17 @@ struct hd_struct *add_partition(struct gendisk
> *disk, int partno,
>  			goto out_del;
>  	}
> 
> +	err = hd_ref_init(p);
> +	if (err)
> +		goto out_remove_file;
> +
>  	/* everything is up and running, commence */
>  	rcu_assign_pointer(ptbl->part[partno], p);
> 
>  	/* suppress uevent if the disk suppresses it */
>  	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);
> @@ -378,6 +380,9 @@ out_free_stats:
>  out_free:
>  	kfree(p);
>  	return ERR_PTR(err);
> +out_remove_file:
> +	if (flags & ADDPART_FLAG_WHOLEDISK)
> +		device_remove_file(pdev, &dev_attr_whole_disk);
>  out_del:
>  	kobject_put(p->holder_dir);
>  	device_del(pdev);

Looks good,
Reviewed-by: Johannes Thumshirn <jthumshirn@...e.de>