nvme-tcp: fix a possible UAF when failing to send request

[Max Gurtovoy]

hi

On 10/02/2025 13:16, zhang.guanghui at cestc.cn wrote:
> Hi，
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>       Thank you for your reply.
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>       In nvme-rdma we use nvme_host_path_error(rq) ,   the prerequisites are -EIO,  ignore this condition?
>   in nvme-tcp this judgment condition is different,  use the function nvme_host_path_error ,
> it should be possible to go to nvme_complete_rq ->  nvme_retry_req -- request->mq_hctx have been freed, is NULL.

did you try the proposal or are you assuming it will be NULL ?


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> zhang.guanghui at cestc.cn
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> From: Max Gurtovoy
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> Date: 2025-02-10 18:24
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> To: Maurizio Lombardi; zhang.guanghui at cestc.cn; sagi; kbusch; sashal; chunguang.xu
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> CC: linux-kernel; linux-nvme; linux-block
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> Subject: Re: nvme-tcp: fix a possible UAF when failing to send request
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> On 10/02/2025 12:01, Maurizio Lombardi wrote:
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>> On Mon Feb 10, 2025 at 8:41 AM CET, zhang.guanghui at cestc.cn wrote:
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>>> Hello
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>> I guess you have to fix your mail client.
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>>>        When using the nvme-tcp driver in a storage cluster, the driver may trigger a null pointer causing the host to crash several times.
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>>> By analyzing the vmcore, we know the direct cause is that  the request->mq_hctx was used after free.
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>>> CPU1                                                                   CPU2
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>>> nvme_tcp_poll                                                          nvme_tcp_try_send  --failed to send reqrest 13
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>> This simply looks like a race condition between nvme_tcp_poll() and nvme_tcp_try_send()
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>> Personally, I would try to fix it inside the nvme-tcp driver without
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>> touching the core functions.
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>> Maybe nvme_tcp_poll should just ensure that io_work completes before
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>> calling nvme_tcp_try_recv(), the POLLING flag should then prevent io_work
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>> from getting rescheduled by the nvme_tcp_data_ready() callback.
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>> Maurizio
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> It seems to me that the HOST_PATH_ERROR handling can be improved in
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> nvme-tcp.
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> In nvme-rdma we use nvme_host_path_error(rq) and nvme_cleanup_cmd(rq) in
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> case we fail to submit a command..
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> can you try to replacing nvme_tcp_end_request(blk_mq_rq_from_pdu(req),
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> NVME_SC_HOST_PATH_ERROR); call with the similar logic we use in
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> nvme-rdma for host path error handling ?
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