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

[yukuai (C)]

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(-)