From 2ee668ec56cc5b830bc03b59656613cb943e8027 Mon Sep 17 00:00:00 2001
From: Tony Butler <tonyjbutler@gmail.com>
Date: Mon, 8 Aug 2016 15:29:14 +0100
Subject: [PATCH] MDL-55513 core_filestorage: Touch and test size instead of
 file_exists()

file_exists() can return false when file exists (in certain scenarios)
---
 lib/filestorage/file_storage.php | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/lib/filestorage/file_storage.php b/lib/filestorage/file_storage.php
index 0480bf794ba..38a20a11026 100644
--- a/lib/filestorage/file_storage.php
+++ b/lib/filestorage/file_storage.php
@@ -386,7 +386,8 @@ class file_storage {
         chdir($tmp);
         $result = exec($cmd, $output);
         chdir($currentdir);
-        if (!file_exists($newtmpfile)) {
+        touch($newtmpfile);
+        if (filesize($newtmpfile) === 0) {
             remove_dir($tmp);
             // Cleanup.
             return false;