nvme-auth: use chap->s2 to indicate bidirectional authentication

Commit 546dea18 ("nvme-auth: check chap ctrl_key once constructed")
replaced the condition "if (ctrl->ctrl_key)" (indicating bidirectional
auth) by "if (chap->ctrl_key)", because ctrl->ctrl_key is a resource shared
with sysfs. But chap->ctrl_key is set in
nvme_auth_process_dhchap_challenge() depending on the DHVLEN in the
DH-HMAC-CHAP Challenge message received from the controller, and will thus
be non-NULL for every DH-HMAC-CHAP exchange, even if unidirectional auth
was requested. This will lead to a protocol violation by sending a Success2
message in the unidirectional case (per NVMe base spec 2.0, the
authentication transaction ends after the Success1 message for
unidirectional auth). Use chap->s2 instead, which is non-zero if and only
if the host requested bi-directional authentication from the controller.

Fixes: 546dea18 ("nvme-auth: check chap ctrl_key once constructed")
Signed-off-by: Martin Wilck <mwilck@suse.com>
Reviewed-by: Daniel Wagner <dwagner@suse.de>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Keith Busch <kbusch@kernel.org>

drivers/nvme/host/auth.c

@@ -341,7 +341,7 @@ static int nvme_auth_process_dhchap_success1(struct nvme_ctrl *ctrl,
 	struct nvmf_auth_dhchap_success1_data *data = chap->buf;
 	size_t size = sizeof(*data);
 
-	if (chap->ctrl_key)
+	if (chap->s2)
 		size += chap->hash_len;
 
 	if (size > CHAP_BUF_SIZE) {
@@ -825,7 +825,7 @@ static void nvme_queue_auth_work(struct work_struct *work)
 		goto fail2;
 	}
 
-	if (chap->ctrl_key) {
+	if (chap->s2) {
 		/* DH-HMAC-CHAP Step 5: send success2 */
 		dev_dbg(ctrl->device, "%s: qid %d send success2\n",
 			__func__, chap->qid);