[PATCH v2] nvmet-tcp: fix a segmentation fault during io parsing error

[Hou Pu]

On 2021/3/28 1:13 PM, Grupi, Elad wrote:
> Hi Hou
>
> Even with the code below we will still queue the failed REQ for the first time.
>
> Please mind the code in nvmet_tcp_done_recv_pdu:
> 1. nvmet_req_init will call __nvmet_req_complete with an error status
> 1.1. __nvmet_req_complete will call nvmet_tcp_queue_response
> 2. nvmet_tcp_handle_req_failure will set the flag NVMET_TCP_F_INIT_FAILED
>
> In step 1.1, the failed REQ will be added to the queue anyway because the flag wasn't set yet.
>
> In the previous patch I was adding the REQ back to the queue on nvmet_tcp_fetch_cmd, so it was useful to prevent queueing the REQ over and over again.
> Now I removed that part from the patch, so it means that the REQ will be added only once.

Thanks for the detailed explanation.

I'm fine with v2 or the new version.


Thanks,

Hou

>
> Elad
>
> -----Original Message-----
> From: Hou Pu <houpu.main at gmail.com>
> Sent: Sunday, 28 March 2021 7:04
> To: Grupi, Elad
> Cc: linux-nvme at lists.infradead.org; sagi at grimberg.me; houpu.main at gmail.com
> Subject: RE: [PATCH v2] nvmet-tcp: fix a segmentation fault during io parsing error
>
>
> [EXTERNAL EMAIL]
>
> On Date: Fri, 26 Mar 2021 20:59:41 +0300, Elad Grupi wrote:
>> In case there is an io that contains inline data and it goes to
>> parsing error flow, command response will free command and iov before
>> clearing the data on the socket buffer.
>> This will delay the command response until receive flow is completed.
>>
>> Fixes: 872d26a391da ("nvmet-tcp: add NVMe over TCP target driver")
>> Signed-off-by: Elad Grupi <elad.grupi at dell.com>
>> ---
>>   drivers/nvme/target/tcp.c | 29 +++++++++++++++++++++++------
>>   1 file changed, 23 insertions(+), 6 deletions(-)
> Hi Elad,
> Just noticed that we still queue the failed REQ to the response queue in this version. Am I missing something?
>
> Is this still needed? (I think it is).
> @@ -526,6 +527,12 @@ static void nvmet_tcp_queue_response(struct nvmet_req *req)
>   		container_of(req, struct nvmet_tcp_cmd, req);
>   	struct nvmet_tcp_queue	*queue = cmd->queue;
>   
> +	if (unlikely((cmd->flags & NVMET_TCP_F_INIT_FAILED) &&
> +			nvmet_tcp_has_inline_data(cmd))) {
> +		/* fail the cmd when we finish processing the inline data */
> +		return;
> +	}
> +
>
>
> Thanks,
> Hou
>
>> diff --git a/drivers/nvme/target/tcp.c b/drivers/nvme/target/tcp.c
>> index 70cc507d1565..3bc0caa47873 100644
>> --- a/drivers/nvme/target/tcp.c
>> +++ b/drivers/nvme/target/tcp.c
>> @@ -702,6 +702,17 @@ static int nvmet_tcp_try_send_one(struct nvmet_tcp_queue *queue,
>>   			return 0;
>>   	}
>>
>> +	if (unlikely((cmd->flags & NVMET_TCP_F_INIT_FAILED) &&
>> +			nvmet_tcp_has_data_in(cmd) &&
>> +			nvmet_tcp_has_inline_data(cmd))) {
>> +		/*
>> +		 * wait for inline data before processing the response
>> +		 * so the iov will not be freed
>> +		 */
>> +		queue->snd_cmd = NULL;
>> +		goto done_send;
>> +	}
>> +
>>   	if (cmd->state == NVMET_TCP_SEND_DATA_PDU) {
>>   		ret = nvmet_try_send_data_pdu(cmd);
>>   		if (ret <= 0)
>> @@ -1103,9 +1114,11 @@ static int nvmet_tcp_try_recv_data(struct nvmet_tcp_queue *queue)
>>   		return 0;
>>   	}
>>
>> -	if (!(cmd->flags & NVMET_TCP_F_INIT_FAILED) &&
>> -	    cmd->rbytes_done == cmd->req.transfer_len) {
>> -		cmd->req.execute(&cmd->req);
>> +	if (cmd->rbytes_done == cmd->req.transfer_len) {
>> +		if (unlikely(cmd->flags & NVMET_TCP_F_INIT_FAILED))
>> +			nvmet_tcp_queue_response(&cmd->req);
>> +		else
>> +			cmd->req.execute(&cmd->req);
>>   	}
>>
>>   	nvmet_prepare_receive_pdu(queue);
>> @@ -1143,9 +1156,13 @@ static int nvmet_tcp_try_recv_ddgst(struct nvmet_tcp_queue *queue)
>>   		goto out;
>>   	}
>>
>> -	if (!(cmd->flags & NVMET_TCP_F_INIT_FAILED) &&
>> -	    cmd->rbytes_done == cmd->req.transfer_len)
>> -		cmd->req.execute(&cmd->req);
>> +	if (cmd->rbytes_done == cmd->req.transfer_len) {
>> +		if (unlikely(cmd->flags & NVMET_TCP_F_INIT_FAILED))
>> +			nvmet_tcp_queue_response(&cmd->req);
>> +		else
>> +			cmd->req.execute(&cmd->req);
>> +	}
>> +
>>   	ret = 0;
>>   out:
>>   	nvmet_prepare_receive_pdu(queue);