Fixed dynamic-stack-buffer-overflow in jerry_value_is_syntax_error (#2095)

Fixes issue #2094, which introduced an error caused by jerry_value_is_syntax_error.
The problem was that the function used strcmp instead of strncmp while checking if err_str_buf contains syntax error and it caused buffer overflow.

JerryScript-DCO-1.0-Signed-off-by: Robert Fancsik frobert@inf.u-szeged.hu

targets/nuttx-stm32f4/jerry_main.c

@@ -147,6 +147,14 @@ jerry_value_is_syntax_error (jerry_value_t error_value) /**< error value */
   }
 
   jerry_size_t err_str_size = jerry_get_string_size (error_name);
+  const char syntax_error_str[] = "SyntaxError";
+
+  if (err_str_size != strlen (syntax_error_str) - 1)
+  {
+    jerry_release_value (error_name);
+    return false;
+  }
+
   jerry_char_t err_str_buf[err_str_size];
 
   jerry_size_t sz = jerry_string_to_char_buffer (error_name, err_str_buf, err_str_size);
@@ -157,7 +165,7 @@ jerry_value_is_syntax_error (jerry_value_t error_value) /**< error value */
     return false;
   }
 
-  if (!strcmp ((char *) err_str_buf, "SyntaxError"))
+  if (!strncmp ((char *) err_str_buf, syntax_error_str, sizeof (syntax_error_str) - 1))
   {
     return true;
   }

targets/tizenrt-artik053/apps/jerryscript/jerry_main.c

@@ -149,6 +149,14 @@ jerry_value_is_syntax_error (jerry_value_t error_value) /**< error value */
   }
 
   jerry_size_t err_str_size = jerry_get_string_size (error_name);
+  const char syntax_error_str[] = "SyntaxError";
+
+  if (err_str_size != strlen (syntax_error_str) - 1)
+  {
+    jerry_release_value (error_name);
+    return false;
+  }
+
   jerry_char_t err_str_buf[err_str_size];
 
   jerry_size_t sz = jerry_string_to_char_buffer (error_name, err_str_buf, err_str_size);
@@ -159,7 +167,7 @@ jerry_value_is_syntax_error (jerry_value_t error_value) /**< error value */
     return false;
   }
 
-  if (!strcmp ((char *) err_str_buf, "SyntaxError"))
+  if (!strncmp ((char *) err_str_buf, syntax_error_str, sizeof (syntax_error_str) - 1))
   {
     return true;
   }