diff --git a/drivers/of/device.c b/drivers/of/device.c
index 3a547793135c318af87116f77cb72eebb3b192be..93f08f18f6b3af2c14e442adef062689b55d88aa 100644
--- a/drivers/of/device.c
+++ b/drivers/of/device.c
@@ -231,14 +231,15 @@ static ssize_t of_device_get_modalias(struct device *dev, char *str, ssize_t len
 	csize = snprintf(str, len, "of:N%pOFn%c%s", dev->of_node, 'T',
 			 of_node_get_device_type(dev->of_node));
 	tsize = csize;
+	if (csize >= len)
+		csize = len > 0 ? len - 1 : 0;
 	len -= csize;
-	if (str)
-		str += csize;
+	str += csize;
 
 	of_property_for_each_string(dev->of_node, "compatible", p, compat) {
 		csize = strlen(compat) + 1;
 		tsize += csize;
-		if (csize > len)
+		if (csize >= len)
 			continue;
 
 		csize = snprintf(str, len, "C%s", compat);