label: fix writing out of bounds in LV_LABEL_LONG_FOT mode #1364

src/lv_objx/lv_label.c

@@ -1303,10 +1303,18 @@ static void lv_label_refr_text(lv_obj_t * label)
             p.y -= style->text.line_space;                                               /*Trim the last line space*/
             uint32_t letter_id = lv_label_get_letter_on(label, &p);
 
-            /*Save letters under the dots and replace them with dots*/
-            uint32_t i;
+
+            /*Be sure there is space for the dots*/
+            size_t txt_len = strlen(ext->text);
             uint32_t byte_id     = lv_txt_encoded_get_byte_id(ext->text, letter_id);
+            while(byte_id + LV_LABEL_DOT_NUM > txt_len) {
+                byte_id -= lv_txt_encoded_size(&ext->text[byte_id]);
+                letter_id--;
+            }
+
+            /*Save letters under the dots and replace them with dots*/
             uint32_t byte_id_ori = byte_id;
+            uint32_t i;
             uint8_t len          = 0;
             for(i = 0; i <= LV_LABEL_DOT_NUM; i++) {
                 len += lv_txt_encoded_size(&ext->text[byte_id]);