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Message-ID: <ae7a6b56-14c6-02e6-6e4b-572c23178049@huaweicloud.com>
Date:   Mon, 6 Nov 2023 20:44:41 +0800
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Subject: Re: [PATCH] nbd: fix uaf in nbd_open
To:     Christoph Hellwig <hch@lst.de>
Cc:     josef@toxicpanda.com, linux-kernel@vger.kernel.org,
        linux-block@vger.kernel.org, nbd@other.debian.org, axboe@kernel.dk,
        chaitanya.kulkarni@wdc.com, yukuai1@huaweicloud.com,
        houtao1@huawei.com, yi.zhang@huawei.com, yangerkun@huawei.com,
        lilingfeng3@huawei.com
References: <20231103101334.1750094-1-lilingfeng@huaweicloud.com>
 <20231103081251.GB16854@lst.de>
From:   Li Lingfeng <lilingfeng@huaweicloud.com>
In-Reply-To: <20231103081251.GB16854@lst.de>
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在 2023/11/3 16:12, Christoph Hellwig 写道:
> On Fri, Nov 03, 2023 at 06:13:34PM +0800, Li Lingfeng wrote:
>> From: Li Lingfeng <lilingfeng3@huawei.com>
>>
>> Commit 4af5f2e03013 ("nbd: use blk_mq_alloc_disk and
>> blk_cleanup_disk") cleans up disk by blk_cleanup_disk() and it won't set
>> disk->private_data as NULL as before. UAF may be triggered in nbd_open()
>> if someone tries to open nbd device right after nbd_put() since refcount
>> of nbd device is zero and private_data is not NULL.
> I don't think this is the right fix.  nbd needs to move to ->free_disk
> to free it's private data.
Thanks for your advice, I will send v2 soon.