nvmet: nul-terminate the NQNs passed in the connect command

The host and subsystem NQNs are passed in the connect command payload and
interpreted as nul-terminated strings.  Ensure they actually are
nul-terminated before using them.

Fixes: a07b4970 "nvmet: add a generic NVMe target")
Reported-by: Alon Zahavi <zahavi.alon@gmail.com>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Keith Busch <kbusch@kernel.org>

drivers/nvme/target/fabrics-cmd.c

@@ -244,6 +244,8 @@ static void nvmet_execute_admin_connect(struct nvmet_req *req)
 		goto out;
 	}
 
+	d->subsysnqn[NVMF_NQN_FIELD_LEN - 1] = '\0';
+	d->hostnqn[NVMF_NQN_FIELD_LEN - 1] = '\0';
 	status = nvmet_alloc_ctrl(d->subsysnqn, d->hostnqn, req,
 				  le32_to_cpu(c->kato), &ctrl);
 	if (status)
@@ -313,6 +315,8 @@ static void nvmet_execute_io_connect(struct nvmet_req *req)
 		goto out;
 	}
 
+	d->subsysnqn[NVMF_NQN_FIELD_LEN - 1] = '\0';
+	d->hostnqn[NVMF_NQN_FIELD_LEN - 1] = '\0';
 	ctrl = nvmet_ctrl_find_get(d->subsysnqn, d->hostnqn,
 				   le16_to_cpu(d->cntlid), req);
 	if (!ctrl) {