linux-kernel - Re: [patch v8 0/7] handle unexpected message from server

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Date:   Fri, 15 Oct 2021 16:19:47 +0800
From:   "yukuai (C)" <yukuai3@...wei.com>
To:     <josef@...icpanda.com>, <axboe@...nel.dk>, <ming.lei@...hat.com>,
        <hch@...radead.org>
CC:     <linux-block@...r.kernel.org>, <nbd@...er.debian.org>,
        <linux-kernel@...r.kernel.org>, <yi.zhang@...wei.com>
Subject: Re: [patch v8 0/7] handle unexpected message from server

On 2021/10/08 15:17, yukuai (C) wrote:
> 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 ...

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(-)
>>>>