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From: Ming Lei <ming.lei@redhat.com>
To: Yu Kuai <yukuai3@huawei.com>
Cc: josef@toxicpanda.com, axboe@kernel.dk,
	linux-block@vger.kernel.org, nbd@other.debian.org,
	linux-kernel@vger.kernel.org, yi.zhang@huawei.com
Subject: Re: [PATCH v9] nbd: fix uaf in nbd_handle_reply()
Date: Fri, 17 Sep 2021 11:33:55 +0800	[thread overview]
Message-ID: <YUQMo1afA8v5/RJW@T590.Home> (raw)
In-Reply-To: <20210916141810.2325276-1-yukuai3@huawei.com>

On Thu, Sep 16, 2021 at 10:18:10PM +0800, Yu Kuai wrote:
> There is a problem that nbd_handle_reply() might access freed request:
> 
> 1) At first, a normal io is submitted and completed with scheduler:
> 
> internel_tag = blk_mq_get_tag -> get tag from sched_tags
>  blk_mq_rq_ctx_init
>   sched_tags->rq[internel_tag] = sched_tag->static_rq[internel_tag]
> ...
> blk_mq_get_driver_tag
>  __blk_mq_get_driver_tag -> get tag from tags
>  tags->rq[tag] = sched_tag->static_rq[internel_tag]
> 
> So, both tags->rq[tag] and sched_tags->rq[internel_tag] are pointing
> to the request: sched_tags->static_rq[internal_tag]. Even if the
> io is finished.
> 
> 2) nbd server send a reply with random tag directly:
> 
> recv_work
>  nbd_handle_reply
>   blk_mq_tag_to_rq(tags, tag)
>    rq = tags->rq[tag]
> 
> 3) if the sched_tags->static_rq is freed:
> 
> blk_mq_sched_free_requests
>  blk_mq_free_rqs(q->tag_set, hctx->sched_tags, i)
>   -> step 2) access rq before clearing rq mapping
>   blk_mq_clear_rq_mapping(set, tags, hctx_idx);
>   __free_pages() -> rq is freed here
> 
> 4) Then, nbd continue to use the freed request in nbd_handle_reply
> 
> Fix the problem by get 'q_usage_counter' before blk_mq_tag_to_rq(),
> thus request is ensured not to be freed because 'q_usage_counter' is
> not zero.
> 
> Signed-off-by: Yu Kuai <yukuai3@huawei.com>
> ---
> Changes in v9:
>  - move percpu_ref_put() behind.

Looks fine:

Reviewed-by: Ming Lei <ming.lei@redhat.com>

-- 
Ming


  reply	other threads:[~2021-09-17  3:33 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-16  9:33 [patch v8 0/7] handle unexpected message from server Yu Kuai
2021-09-16  9:33 ` [patch v8 1/7] nbd: don't handle response without a corresponding request message Yu Kuai
2021-09-16  9:33 ` [patch v8 2/7] nbd: make sure request completion won't concurrent Yu Kuai
2021-09-16  9:33 ` [patch v8 3/7] nbd: check sock index in nbd_read_stat() Yu Kuai
2021-09-19 10:34   ` yukuai (C)
2021-09-22  9:22     ` Ming Lei
2021-09-22 12:12       ` Eric Blake
2021-09-22 12:21       ` yukuai (C)
2021-09-22 15:56       ` Wouter Verhelst
2021-09-23  0:29   ` Ming Lei
2021-09-16  9:33 ` [patch v8 4/7] nbd: don't start request if nbd_queue_rq() failed Yu Kuai
2021-09-16 12:48   ` Ming Lei
2021-09-16  9:33 ` [patch v8 5/7] nbd: clean up return value checking of sock_xmit() Yu Kuai
2021-09-16 12:49   ` Ming Lei
2021-09-16  9:33 ` [patch v8 6/7] nbd: partition nbd_read_stat() into nbd_read_reply() and nbd_handle_reply() Yu Kuai
2021-09-16 12:53   ` Ming Lei
2021-09-16  9:33 ` [patch v8 7/7] nbd: fix uaf in nbd_handle_reply() Yu Kuai
2021-09-16 12:58   ` Ming Lei
2021-09-16 13:10     ` yukuai (C)
2021-09-16 13:55       ` Ming Lei
2021-09-16 14:05         ` yukuai (C)
2021-09-16 14:18   ` [PATCH v9] " Yu Kuai
2021-09-17  3:33     ` Ming Lei [this message]
2021-10-17 13:09     ` Jens Axboe
2021-09-23 13:33 ` [patch v8 0/7] handle unexpected message from server yukuai (C)
2021-09-29 12:54   ` yukuai (C)
2021-10-08  7:17     ` yukuai (C)
2021-10-15  8:19       ` yukuai (C)
2021-10-15 16:08 ` Josef Bacik
2021-10-17 13:09 ` Jens Axboe

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