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

Index: core/fpdfapi/fpdf_edit/fpdf_edit_create.cpp
diff --git a/core/fpdfapi/fpdf_edit/fpdf_edit_create.cpp b/core/fpdfapi/fpdf_edit/fpdf_edit_create.cpp
index d29b9834fa1e731e0e0ee48e67556da4fe0e2405..80fb3a4edfba2da99dcbbb37bc31f9cf570b26d7 100644
--- a/core/fpdfapi/fpdf_edit/fpdf_edit_create.cpp
+++ b/core/fpdfapi/fpdf_edit/fpdf_edit_create.cpp
@@ -1495,7 +1495,9 @@ int32_t CPDF_Creator::WriteDoc_Stage1(IFX_Pause* pPause) {
       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) {