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Date:   Tue, 19 Jul 2022 09:03:06 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Hannes Reinecke <hare@suse.de>
Cc:     Christoph Hellwig <hch@lst.de>, Song Liu <song@kernel.org>,
        Logan Gunthorpe <logang@deltatee.com>,
        linux-raid@vger.kernel.org, linux-block@vger.kernel.org
Subject: Re: [PATCH 08/10] md: stop using for_each_mddev in md_exit
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On Mon, Jul 18, 2022 at 09:10:59AM +0200, Hannes Reinecke wrote:
>
> Having thought about it some more ... wouldn't it make sense to modify 
> mddev_get() to
>
> if (atomic_inc_not_zero(&mddev->active))
>     return NULL;
>
> to ensure we're not missing any use-after-free issues, which previously 
> would have been caught by the 'for_each_mddev()' macro?

No.  mddev->active = 0 can still be a perfectly valid mddev and they
are not automatically deleted.  Check the conditions in mddev_put.