From: Ming Lei <ming.lei@redhat.com>
To: Yu Kuai <yukuai3@huawei.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 09:11:43 +0800 [thread overview]
Message-ID: <YT/2z4PSeW5oJWMq@T590> (raw)
In-Reply-To: <20210909141256.2606682-6-yukuai3@huawei.com>
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.
Thanks,
Ming
next prev parent reply other threads:[~2021-09-14 1:11 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 [this message]
2021-09-14 3:11 ` yukuai (C)
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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