Relax the check on 0 length streams.

core/src/fpdfapi/fpdf_parser/fpdf_parser_parser.cpp

Index: core/src/fpdfapi/fpdf_parser/fpdf_parser_parser.cpp
diff --git a/core/src/fpdfapi/fpdf_parser/fpdf_parser_parser.cpp b/core/src/fpdfapi/fpdf_parser/fpdf_parser_parser.cpp
index 984e08d882cd04f95c9ce223500c18ac8ac40f3e..4dde9836b45273e00a1a4231639e4b48e167fa34 100644
--- a/core/src/fpdfapi/fpdf_parser/fpdf_parser_parser.cpp
+++ b/core/src/fpdfapi/fpdf_parser/fpdf_parser_parser.cpp
@@ -2528,11 +2528,14 @@ CPDF_Stream* CPDF_SyntaxParser::ReadStream(CPDF_Dictionary* pDict,
     }
     m_Pos = streamStartPos;
   }
-  if (len <= 0) {
+  if (len < 0) {
     return nullptr;
   }
-  uint8_t* pData = FX_Alloc(uint8_t, len);
-  ReadBlock(pData, len);
+  uint8_t* pData = nullptr;
+  if (len > 0) {
+    pData = FX_Alloc(uint8_t, len);
+    ReadBlock(pData, len);
+  }
   if (pCryptoHandler) {

[jun_fang, 2015/10/08 09:19:52]

If pData is nullptr, there is no data to be decrypted. 
It should be changed to "if (pCryptoHandler && pData) {"

[Lei Zhang, 2015/10/08 17:21:49]

Ok. Since |pData| can only be a nullptr when len == 0, I just moved this block
into the if (len > 0) block.

     CFX_BinaryBuf dest_buf;
     dest_buf.EstimateSize(pCryptoHandler->DecryptGetSize(len));