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Subject: Re: [patch v8 0/7] handle unexpected message from server
From:   "yukuai (C)" <yukuai3@huawei.com>
To:     <josef@toxicpanda.com>, <axboe@kernel.dk>, <ming.lei@redhat.com>,
        <hch@infradead.org>
CC:     <linux-block@vger.kernel.org>, <nbd@other.debian.org>,
        <linux-kernel@vger.kernel.org>, <yi.zhang@huawei.com>
References: <20210916093350.1410403-1-yukuai3@huawei.com>
 <f56cc608-ac55-0eee-f3d0-19ba1a8c22ef@huawei.com>
 <37b222c1-d6b0-3e46-248a-2557db40ae92@huawei.com>
Message-ID: <5effbc3a-e2f5-063f-6a20-985016d390c6@huawei.com>
Date:   Fri, 8 Oct 2021 15:17:25 +0800
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On 2021/09/29 20:54, yukuai (C) wrote:
> On 2021/09/23 21:33, yukuai (C) wrote:
>> On 2021/09/16 17:33, Yu Kuai wrote:
>>
>> Hi, jens
>>
>> Any interest to apply this series?
> 
> friendly ping ...

Hi, Jens

friendly ping again ...
>>
>> Thanks,
>> Kuai
>>> This patch set tries to fix that client might oops if nbd server send
>>> unexpected message to client, for example, our syzkaller report a uaf
>>> in nbd_read_stat():
>>>
>>> Call trace:
>>>   dump_backtrace+0x0/0x310 arch/arm64/kernel/time.c:78
>>>   show_stack+0x28/0x38 arch/arm64/kernel/traps.c:158
>>>   __dump_stack lib/dump_stack.c:77 [inline]
>>>   dump_stack+0x144/0x1b4 lib/dump_stack.c:118
>>>   print_address_description+0x68/0x2d0 mm/kasan/report.c:253
>>>   kasan_report_error mm/kasan/report.c:351 [inline]
>>>   kasan_report+0x134/0x2f0 mm/kasan/report.c:409
>>>   check_memory_region_inline mm/kasan/kasan.c:260 [inline]
>>>   __asan_load4+0x88/0xb0 mm/kasan/kasan.c:699
>>>   __read_once_size include/linux/compiler.h:193 [inline]
>>>   blk_mq_rq_state block/blk-mq.h:106 [inline]
>>>   blk_mq_request_started+0x24/0x40 block/blk-mq.c:644
>>>   nbd_read_stat drivers/block/nbd.c:670 [inline]
>>>   recv_work+0x1bc/0x890 drivers/block/nbd.c:749
>>>   process_one_work+0x3ec/0x9e0 kernel/workqueue.c:2147
>>>   worker_thread+0x80/0x9d0 kernel/workqueue.c:2302
>>>   kthread+0x1d8/0x1e0 kernel/kthread.c:255
>>>   ret_from_fork+0x10/0x18 arch/arm64/kernel/entry.S:1174
>>>
>>> 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_read_stat
>>>    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_read_stat()
>>>
>>> Changes in v8:
>>>   - add patch 5 to this series.
>>>   - modify some words.
>>> Changes in v7:
>>>   - instead of exposing blk_queue_exit(), using percpu_ref_put()
>>>   directly.
>>>   - drop the ref right after nbd_handle_reply().
>>> Changes in v6:
>>>   - don't set cmd->status to error if request is completed before
>>>   nbd_clear_req().
>>>   - get 'q_usage_counter' to prevent accessing freed request through
>>>   blk_mq_tag_to_rq(), instead of using blk_mq_find_and_get_req().
>>> Changes in v5:
>>>   - move patch 1 & 2 in v4 (patch 4 & 5 in v5) behind
>>>   - add some comment in patch 5
>>> Changes in v4:
>>>   - change the name of the patchset, since uaf is not the only problem
>>>   if server send unexpected reply message.
>>>   - instead of adding new interface, use blk_mq_find_and_get_req().
>>>   - add patch 5 to this series
>>> Changes in v3:
>>>   - v2 can't fix the problem thoroughly, add patch 3-4 to this series.
>>>   - modify descriptions.
>>>   - patch 5 is just a cleanup
>>> Changes in v2:
>>>   - as Bart suggested, add a new helper function for drivers to get
>>>   request by tag.
>>>
>>> Yu Kuai (7):
>>>    nbd: don't handle response without a corresponding request message
>>>    nbd: make sure request completion won't concurrent
>>>    nbd: check sock index in nbd_read_stat()
>>>    nbd: don't start request if nbd_queue_rq() failed
>>>    nbd: clean up return value checking of sock_xmit()
>>>    nbd: partition nbd_read_stat() into nbd_read_reply() and
>>>      nbd_handle_reply()
>>>    nbd: fix uaf in nbd_handle_reply()
>>>
>>>   drivers/block/nbd.c | 135 +++++++++++++++++++++++++++++++-------------
>>>   1 file changed, 96 insertions(+), 39 deletions(-)
>>>