[PATCH] nvme-tcp: Prevent infinite loop if socket closes during CONNECTING state

[Hannes Reinecke]

On 1/21/25 14:45, Maurizio Lombardi wrote:
> There is a potential race condition that can occur if
> the target closes the socket while the host is in the CONNECTING state.
> 
> If the socket's state changes to TCP_CLOSE, the nvme_tcp_state_change()
> function is invoked. However, nvme_tcp_error_recovery() is unable
> to transition the controller state to NVME_CTRL_RESETTING because
> the controller is still in the CONNECTING state. As a result, error
> recovery is bypassed, and the controller incorrectly transitions
> to the LIVE state with closed sockets.
> 
> Subsequent attempts by the host to communicate with the target
> will result in an infinite loop.
> 
> Fix the bug by checking for the -EPIPE error code, which indicates
> that the connection was closed by the target. If this condition
> is detected, ensure the error recovery process is initiated to correctly
> handle the disconnection.
> 
> Signed-off-by: Maurizio Lombardi <mlombard at redhat.com>
> ---
>   drivers/nvme/host/tcp.c | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c
> index 841238f38fdd..d0bb225dca23 100644
> --- a/drivers/nvme/host/tcp.c
> +++ b/drivers/nvme/host/tcp.c
> @@ -1261,6 +1261,8 @@ static int nvme_tcp_try_send(struct nvme_tcp_queue *queue)
>   			"failed to send request %d\n", ret);
>   		nvme_tcp_fail_request(queue->request);
>   		nvme_tcp_done_send_req(queue);
> +		if (ret == -EPIPE)
> +			nvme_tcp_error_recovery(&queue->ctrl->ctrl);
>   	}
>   out:
>   	memalloc_noreclaim_restore(noreclaim_flag);

This feels a bit weird; wouldn't it be better to allow transitions
from 'CONNECTING' to 'RESETTING'? Wouldn't the fix the issue, too?
But yeah, this is a real issue; I've seen it in my tests occasionally,
too.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
hare at suse.de                                +49 911 74053 688
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