Bail out on bad size and height in CCodec_FaxDecoder::CreateDecoder

testing/libfuzzer/pdf_codec_fax_fuzzer.cc

 // Copyright 2016 The 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.
 
 #include <cstdint>
 #include <memory>
 
 #include "core/fxcodec/codec/ccodec_faxmodule.h"
 #include "core/fxcodec/codec/ccodec_scanlinedecoder.h"
 
@@ skipping 11 matching lines @@
   int K = GetInteger(data + 8);
   int Columns = GetInteger(data + 12);
   int Rows = GetInteger(data + 16);
   FX_BOOL EndOfLine = (data[20] & 0x01) == 0;
   FX_BOOL ByteAlign = (data[20] & 0x02) == 0;
   FX_BOOL BlackIs1 = (data[20] & 0x04) == 0;
   data += kParameterSize;
   size -= kParameterSize;
 
   CCodec_FaxModule fax_module;
   std::unique_ptr<CCodec_ScanlineDecoder> decoder;

[Tom Sepez, 2016/09/23 16:05:33]

nit: combine wth next line

std::unique_ptr<CCodec_ScanlineDecoder> decoder(
    fax_module.CreateDecoder( ... ));

[Lei Zhang, 2016/09/23 16:15:46]

I have a CL to clean up the nits. So let's just land this.

   decoder.reset(fax_module.CreateDecoder(data, size, width, height, K,
                                          EndOfLine, ByteAlign, BlackIs1,
                                          Columns, Rows));
 
-  int line = 0;
-  while (decoder->GetScanline(line))
-    line++;
+  if (decoder) {
+    int line = 0;
+    while (decoder->GetScanline(line))
+      line++;
+  }
 
   return 0;
 }