Fix PNG decoding divide by zero error due to zero row count.

core/src/fxcodec/codec/fx_codec_flate.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 "../../../../third_party/base/nonstd_unique_ptr.h"
 #include "../../../../third_party/zlib_v128/zlib.h"
 #include "../../../include/fxcodec/fx_codec.h"
 #include "../../../include/fxcodec/fx_codec_flate.h"
@@ skipping 382 matching lines @@
 static FX_BOOL PNG_Predictor(uint8_t*& data_buf,
                              FX_DWORD& data_size,
                              int Colors,
                              int BitsPerComponent,
                              int Columns) {
   const int BytesPerPixel = (Colors * BitsPerComponent + 7) / 8;
   const int row_size = (Colors * BitsPerComponent * Columns + 7) / 8;
   if (row_size <= 0)
     return FALSE;
   const int row_count = (data_size + row_size) / (row_size + 1);
+  if (row_count <= 0)

[Tom Sepez, 2015/10/02 16:44:25]

Yeah, ok, but this gets better using only unsigned types and safe types for
overflow handling. I'm sure there's some lurking grief if you can call this with
arbitrary arguments.

[Lei Zhang, 2015/10/02 17:29:31]

Acknowledged.

+    return FALSE;
   const int last_row_size = data_size % (row_size + 1);
   uint8_t* dest_buf = FX_Alloc2D(uint8_t, row_size, row_count);
   int byte_cnt = 0;
   uint8_t* pSrcData = data_buf;
   uint8_t* pDestData = dest_buf;
   for (int row = 0; row < row_count; row++) {
     uint8_t tag = pSrcData[0];
     byte_cnt++;
     if (tag == 0) {
       int move_size = row_size;
@@ skipping 553 matching lines @@
                                    FX_DWORD src_size,
                                    uint8_t*& dest_buf,
                                    FX_DWORD& dest_size) {
   dest_size = src_size + src_size / 1000 + 12;
   dest_buf = FX_Alloc(uint8_t, dest_size);
   unsigned long temp_size = dest_size;
   FPDFAPI_FlateCompress(dest_buf, &temp_size, src_buf, src_size);
   dest_size = (FX_DWORD)temp_size;
   return TRUE;
 }