From: "yukuai (C)" <yukuai3@huawei.com>
To: Ming Lei <ming.lei@redhat.com>
Cc: <axboe@kernel.dk>, <josef@toxicpanda.com>, <hch@infradead.org>,
<linux-block@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
<nbd@other.debian.org>, <yi.zhang@huawei.com>
Subject: Re: [PATCH v5 5/6] nbd: convert to use blk_mq_find_and_get_req()
Date: Tue, 14 Sep 2021 11:11:06 +0800 [thread overview]
Message-ID: <c6af73a2-f12d-eeef-616e-ae0cdb4f6f2d@huawei.com> (raw)
In-Reply-To: <YT/2z4PSeW5oJWMq@T590>
On 2021/09/14 9:11, Ming Lei wrote:
> On Thu, Sep 09, 2021 at 10:12:55PM +0800, Yu Kuai wrote:
>> blk_mq_tag_to_rq() can only ensure to return valid request in
>> following situation:
>>
>> 1) client send request message to server first
>> submit_bio
>> ...
>> blk_mq_get_tag
>> ...
>> blk_mq_get_driver_tag
>> ...
>> nbd_queue_rq
>> nbd_handle_cmd
>> nbd_send_cmd
>>
>> 2) client receive respond message from server
>> recv_work
>> nbd_read_stat
>> blk_mq_tag_to_rq
>>
>> If step 1) is missing, blk_mq_tag_to_rq() will return a stale
>> request, which might be freed. Thus convert to use
>> blk_mq_find_and_get_req() to make sure the returned request is not
>> freed.
>
> But NBD_CMD_INFLIGHT has been added for checking if the reply is
> expected, do we still need blk_mq_find_and_get_req() for covering
> this issue? BTW, request and its payload is pre-allocated, so there
> isn't real use-after-free.
Hi, Ming
Checking NBD_CMD_INFLIGHT relied on the request founded by tag is valid,
not the other way round.
nbd_read_stat
req = blk_mq_tag_to_rq()
cmd = blk_mq_rq_to_pdu(req)
mutex_lock(cmd->lock)
checking NBD_CMD_INFLIGHT
The checking doesn't have any effect on blk_mq_tag_to_rq().
Thanks,
Kuai
next prev parent reply other threads:[~2021-09-14 3:11 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-09 14:12 [PATCH v5 0/6] handle unexpected message from server Yu Kuai
2021-09-09 14:12 ` [PATCH v5 1/6] nbd: don't handle response without a corresponding request message Yu Kuai
2021-09-14 0:54 ` Ming Lei
2021-09-09 14:12 ` [PATCH v5 2/6] nbd: make sure request completion won't concurrent Yu Kuai
2021-09-14 0:57 ` Ming Lei
2021-09-14 3:11 ` yukuai (C)
2021-09-09 14:12 ` [PATCH v5 3/6] nbd: check sock index in nbd_read_stat() Yu Kuai
2021-09-09 14:12 ` [PATCH v5 4/6] blk-mq: export two symbols to get request by tag Yu Kuai
2021-09-09 14:12 ` [PATCH v5 5/6] nbd: convert to use blk_mq_find_and_get_req() Yu Kuai
2021-09-14 1:11 ` Ming Lei
2021-09-14 3:11 ` yukuai (C) [this message]
2021-09-14 6:44 ` Ming Lei
2021-09-14 7:13 ` yukuai (C)
2021-09-14 7:46 ` Ming Lei
2021-09-14 9:08 ` yukuai (C)
2021-09-14 9:12 ` yukuai (C)
2021-09-14 14:33 ` Ming Lei
2021-09-14 9:19 ` yukuai (C)
2021-09-14 14:37 ` Ming Lei
2021-09-15 1:54 ` yukuai (C)
2021-09-15 3:16 ` Ming Lei
2021-09-15 3:36 ` yukuai (C)
2021-09-15 3:46 ` Ming Lei
2021-09-09 14:12 ` [PATCH v5 6/6] nbd: don't start request if nbd_queue_rq() failed Yu Kuai
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