MAGETWO-23679: Unable to place order with product with custom option 'file'

Author: Dale Sikkema

lib/internal/Magento/Framework/Filesystem/DirectoryList.php

@@ -96,7 +96,7 @@ public function __construct($root, array $config = [])
         static::validate($config);
         $this->root = $this->filterPath($root);
         $this->directories = static::getDefaultConfig();
-        $this->directories[self::SYS_TMP] = [self::PATH => sys_get_temp_dir()];
+        $this->directories[self::SYS_TMP] = [self::PATH => realpath(sys_get_temp_dir())];
 
         // inject custom values from constructor
         foreach ($this->directories as $code => $dir) {