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Subject: Re: [PATCH] blk-mq: only unregister sysfs when registration succeeded
To:     Yu Kuai <yukuai1@huaweicloud.com>,
        Liu Shixin <liushixin2@huawei.com>,
        Jens Axboe <axboe@kernel.dk>
Cc:     linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
        "yukuai (C)" <yukuai3@huawei.com>
References: <20221112110754.1109979-1-liushixin2@huawei.com>
 <607beb5b-8d54-b795-8a05-76352d7ed863@huaweicloud.com>
From:   Yu Kuai <yukuai1@huaweicloud.com>
Message-ID: <58ab3673-3e39-9ea9-1749-eebfcfb8a10f@huaweicloud.com>
Date:   Sat, 12 Nov 2022 18:57:07 +0800
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?? 2022/11/12 18:44, Yu Kuai д??:
> Hi,
> 
> ?? 2022/11/12 19:07, Liu Shixin д??:
>> kobject_del() must not be called if kobject_add() has not been called.
>> Hence only unregister sysfs when registration succeeded.
>>
> 
>  From what I see, the blk_queue_registered() from caller
> blk_unregister_queue() can already prevent that. QUEUE_FLAG_REGISTERED
> will only be set if blk_register_queue() succeed.

I see that the return value of blk_mq_sysfs_register() is not checked
from blk_register_queue(), there will be memleak or uaf from error path.

Hence I think better thing to do is to handle the case that
blk_mq_sysfs_register() faild, and clean up if blk_mq_sysfs_register()
succeed while follow up procedures failed from blk_register_queue().