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* [patch v8 0/7] handle unexpected message from server
@ 2021-09-16  9:33 Yu Kuai
  2021-09-16  9:33 ` [patch v8 1/7] nbd: don't handle response without a corresponding request message Yu Kuai
                   ` (9 more replies)
  0 siblings, 10 replies; 30+ messages in thread
From: Yu Kuai @ 2021-09-16  9:33 UTC (permalink / raw)
  To: josef, axboe, ming.lei, hch
  Cc: linux-block, nbd, linux-kernel, yukuai3, yi.zhang

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(-)

-- 
2.31.1


^ permalink raw reply	[flat|nested] 30+ messages in thread

end of thread, other threads:[~2021-10-17 13:09 UTC | newest]

Thread overview: 30+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
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
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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