Revert kvec msg iterator before trying to process a TLS alert
when possible.

In nvmet_tcp_try_recv_data(), it's assumed that no msg control
message buffer is set prior to sock_recvmsg(). Hannes suggested
that upon detecting that TLS control message is received log a
message and error out. Left comments in the code for the future
improvements.

Fixes: a1c5dd8355b1 ("nvmet-tcp: control messages for recvmsg()")
Suggested-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Hannes Reinecky <hare@susu.de>
Signed-off-by: Olga Kornievskaia <okorniev@redhat.com>
---
 drivers/nvme/target/tcp.c | 31 +++++++++++++++++++------------
 1 file changed, 19 insertions(+), 12 deletions(-)

diff --git a/drivers/nvme/target/tcp.c b/drivers/nvme/target/tcp.c
index 688033b88d38..98cee10de713 100644
--- a/drivers/nvme/target/tcp.c
+++ b/drivers/nvme/target/tcp.c
@@ -120,7 +120,6 @@ struct nvmet_tcp_cmd {
 	u32				pdu_len;
 	u32				pdu_recv;
 	int				sg_idx;
-	char				recv_cbuf[CMSG_LEN(sizeof(char))];
 	struct msghdr			recv_msg;
 	struct bio_vec			*iov;
 	u32				flags;
@@ -1161,6 +1160,7 @@ static int nvmet_tcp_try_recv_pdu(struct nvmet_tcp_queue *queue)
 	if (unlikely(len < 0))
 		return len;
 	if (queue->tls_pskid) {
+		iov_iter_revert(&msg.msg_iter, len);
 		ret = nvmet_tcp_tls_record_ok(queue, &msg, cbuf);
 		if (ret < 0)
 			return ret;
@@ -1217,19 +1217,28 @@ static void nvmet_tcp_prep_recv_ddgst(struct nvmet_tcp_cmd *cmd)
 static int nvmet_tcp_try_recv_data(struct nvmet_tcp_queue *queue)
 {
 	struct nvmet_tcp_cmd  *cmd = queue->cmd;
-	int len, ret;
+	int len;
 
 	while (msg_data_left(&cmd->recv_msg)) {
+		/* to detect that we received a TlS alert, we assumed that
+		 * cmg->recv_msg's control buffer is not setup. kTLS will
+		 * return an error when no control buffer is set and
+		 * non-tls-data payload is received.
+		 */
 		len = sock_recvmsg(cmd->queue->sock, &cmd->recv_msg,
 			cmd->recv_msg.msg_flags);
+		if (cmd->recv_msg.msg_flags & MSG_CTRUNC) {
+			if (len == 0 || len == -EIO) {
+				pr_err("queue %d: unhandled control message\n",
+				       queue->idx);
+				/* note that unconsumed TLS control message such
+				 * as TLS alert is still on the socket.
+				 */
+				return -EAGAIN;
+			}
+		}
 		if (len <= 0)
 			return len;
-		if (queue->tls_pskid) {
-			ret = nvmet_tcp_tls_record_ok(cmd->queue,
-					&cmd->recv_msg, cmd->recv_cbuf);
-			if (ret < 0)
-				return ret;
-		}
 
 		cmd->pdu_recv += len;
 		cmd->rbytes_done += len;
@@ -1267,6 +1276,7 @@ static int nvmet_tcp_try_recv_ddgst(struct nvmet_tcp_queue *queue)
 	if (unlikely(len < 0))
 		return len;
 	if (queue->tls_pskid) {
+		iov_iter_revert(&msg.msg_iter, len);
 		ret = nvmet_tcp_tls_record_ok(queue, &msg, cbuf);
 		if (ret < 0)
 			return ret;
@@ -1453,10 +1463,6 @@ static int nvmet_tcp_alloc_cmd(struct nvmet_tcp_queue *queue,
 	if (!c->r2t_pdu)
 		goto out_free_data;
 
-	if (queue->state == NVMET_TCP_Q_TLS_HANDSHAKE) {
-		c->recv_msg.msg_control = c->recv_cbuf;
-		c->recv_msg.msg_controllen = sizeof(c->recv_cbuf);
-	}
 	c->recv_msg.msg_flags = MSG_DONTWAIT | MSG_NOSIGNAL;
 
 	list_add_tail(&c->entry, &queue->free_list);
@@ -1736,6 +1742,7 @@ static int nvmet_tcp_try_peek_pdu(struct nvmet_tcp_queue *queue)
 		return len;
 	}
 
+	iov_iter_revert(&msg.msg_iter, len);
 	ret = nvmet_tcp_tls_record_ok(queue, &msg, cbuf);
 	if (ret < 0)
 		return ret;
-- 
2.47.1