IB/iser: Protect iscsi_max_lun module param using callback

Remove the check from the module_init function.

Link: https://lore.kernel.org/r/20210111145754.56727-3-mgurtovoy@nvidia.comReviewed-by: Israel Rukshin <israelr@nvidia.com>
Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

drivers/infiniband/ulp/iser/iscsi_iser.c

@@ -89,9 +89,15 @@ int iser_debug_level = 0;
 module_param_named(debug_level, iser_debug_level, int, S_IRUGO | S_IWUSR);
 MODULE_PARM_DESC(debug_level, "Enable debug tracing if > 0 (default:disabled)");
 
+static int iscsi_iser_set(const char *val, const struct kernel_param *kp);
+static const struct kernel_param_ops iscsi_iser_size_ops = {
+	.set = iscsi_iser_set,
+	.get = param_get_uint,
+};
+
 static unsigned int iscsi_max_lun = 512;
-module_param_named(max_lun, iscsi_max_lun, uint, S_IRUGO);
-MODULE_PARM_DESC(max_lun, "Max LUNs to allow per session (default:512");
+module_param_cb(max_lun, &iscsi_iser_size_ops, &iscsi_max_lun, S_IRUGO);
+MODULE_PARM_DESC(max_lun, "Max LUNs to allow per session, should > 0 (default:512)");
 
 unsigned int iser_max_sectors = ISER_DEF_MAX_SECTORS;
 module_param_named(max_sectors, iser_max_sectors, uint, S_IRUGO | S_IWUSR);
@@ -110,6 +116,18 @@ int iser_pi_guard;
 module_param_named(pi_guard, iser_pi_guard, int, S_IRUGO);
 MODULE_PARM_DESC(pi_guard, "T10-PI guard_type [deprecated]");
 
+static int iscsi_iser_set(const char *val, const struct kernel_param *kp)
+{
+	int ret;
+	unsigned int n = 0;
+
+	ret = kstrtouint(val, 10, &n);
+	if (ret != 0 || n == 0)
+		return -EINVAL;
+
+	return param_set_uint(val, kp);
+}
+
 /*
  * iscsi_iser_recv() - Process a successful recv completion
  * @conn:         iscsi connection
@@ -1009,11 +1027,6 @@ static int __init iser_init(void)
 
 	iser_dbg("Starting iSER datamover...\n");
 
-	if (iscsi_max_lun < 1) {
-		iser_err("Invalid max_lun value of %u\n", iscsi_max_lun);
-		return -EINVAL;
-	}
-
 	memset(&ig, 0, sizeof(struct iser_global));
 
 	ig.desc_cache = kmem_cache_create("iser_descriptors",