Messages in this thread | | | Subject | Re: [patch v8 0/7] handle unexpected message from server | From | "yukuai (C)" <> | Date | Wed, 29 Sep 2021 20:54:48 +0800 |
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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(-) >>
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