[PATCH] nvmet-tcp: Fix the H2C expected PDU len calculation

[Sagi Grimberg]

> The nvmet_tcp_handle_h2c_data_pdu() function should take into
> consideration the possibility that the header digest and/or the data
> digests are enabled when calculating the expected PDU length before
> comparing it to the value stored in cmd->pdu_len.
> 
> Fixes: efa56305908b ("nvmet-tcp: Fix a kernel panic when host sends an invalid H2C PDU length")
> Signed-off-by: Maurizio Lombardi <mlombard at redhat.com>
> ---
>   drivers/nvme/target/tcp.c | 9 ++++++---
>   1 file changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/nvme/target/tcp.c b/drivers/nvme/target/tcp.c
> index 3569c1255c5e..717ea1e5f4c3 100644
> --- a/drivers/nvme/target/tcp.c
> +++ b/drivers/nvme/target/tcp.c
> @@ -979,7 +979,7 @@ static int nvmet_tcp_handle_h2c_data_pdu(struct nvmet_tcp_queue *queue)
>   {
>   	struct nvme_tcp_data_pdu *data = &queue->pdu.data;
>   	struct nvmet_tcp_cmd *cmd;
> -	unsigned int plen;
> +	unsigned int expected_len;
>   
>   	if (likely(queue->nr_cmds)) {
>   		if (unlikely(data->ttag >= queue->nr_cmds)) {
> @@ -999,9 +999,12 @@ static int nvmet_tcp_handle_h2c_data_pdu(struct nvmet_tcp_queue *queue)
>   		goto err_proto;
>   	}
>   
> -	plen = le32_to_cpu(data->hdr.plen);
> +	expected_len = le32_to_cpu(data->hdr.plen);
> +	expected_len -= nvmet_tcp_hdgst_len(queue);
> +	expected_len -= nvmet_tcp_ddgst_len(queue);
> +	expected_len -= sizeof(*data);

I think we should call it exp_data_len.

Why not do:
	exp_data_len = le32_to_cpu(data->hdr.plen) -
			nvmet_tcp_hdgst_len(queue) -
			nvmet_tcp_ddgst_len(queue) -
			sizeof(*data);

>   	cmd->pdu_len = le32_to_cpu(data->data_length);
> -	if (unlikely(cmd->pdu_len != (plen - sizeof(*data)) ||
> +	if (unlikely(cmd->pdu_len != expected_len ||
>   		     cmd->pdu_len == 0 ||
>   		     cmd->pdu_len > NVMET_TCP_MAXH2CDATA)) {
>   		pr_err("H2CData PDU len %u is invalid\n", cmd->pdu_len);