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

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Date:   Wed, 29 Sep 2021 20:54:48 +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 2021/09/23 21:33, yukuai (C) wrote:
> On 2021/09/16 17:33, Yu Kuai wrote:
> 
> Hi, jens
> 
> Any interest to apply this series?

friendly ping ...
> 
> 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(-)
>>