nvme-fabrics: ignore invalid fast_io_fail_tmo values

Valid fast_io_fail_tmo values are integers >= 0 or -1 (disabled).
Prevent userspace from setting arbitrary negative values.
Signed-off-by: Maurizio Lombardi <mlombard@redhat.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

drivers/nvme/host/fabrics.c

@@ -698,6 +698,9 @@ static int nvmf_parse_options(struct nvmf_ctrl_options *opts,
 			if (token >= 0)
 				pr_warn("I/O fail on reconnect controller after %d sec\n",
 					token);
+			else
+				token = -1;
+
 			opts->fast_io_fail_tmo = token;
 			break;
 		case NVMF_OPT_HOSTNQN: