in the attempt to fix 627393, changed IFX_FileRead's readBlock to return the length it reads

core/fpdfapi/fpdf_edit/fpdf_edit_create.cpp

 // Copyright 2014 PDFium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
 
 #include "core/fpdfapi/fpdf_edit/editint.h"
 
 #include <vector>
 
@@ skipping 1477 matching lines @@
       m_iStage = 15;
     }
   }
   if (m_iStage == 15) {
     if ((m_dwFlags & FPDFCREATE_NO_ORIGINAL) == 0 && m_Pos) {
       IFX_FileRead* pSrcFile = m_pParser->GetFileAccess();
       uint8_t buffer[4096];
       uint32_t src_size = (uint32_t)(uintptr_t)m_Pos;
       while (src_size) {
         uint32_t block_size = src_size > 4096 ? 4096 : src_size;
-        if (!pSrcFile->ReadBlock(buffer, m_Offset - src_size, block_size)) {
+        if (pSrcFile->ReadBlock(buffer, m_Offset - src_size, block_size) !=
+                block_size &&
+            !pSrcFile->IsEOF()) {
           return -1;
         }
         if (m_File.AppendBlock(buffer, block_size) < 0) {
           return -1;
         }
         src_size -= block_size;
         if (pPause && pPause->NeedToPauseNow()) {
           m_Pos = (void*)(uintptr_t)src_size;
           return 1;
         }
@@ skipping 504 matching lines @@
   m_pCryptoHandler = nullptr;
 }
 void CPDF_Creator::ResetStandardSecurity() {
   if (!m_bLocalCryptoHandler)
     return;
 
   delete m_pCryptoHandler;
   m_pCryptoHandler = nullptr;
   m_bLocalCryptoHandler = FALSE;
 }