Guard usages of tellp(). It may return -1 in error cases.

Change-Id: I064ddcad8671b9ade2c02142a6c2c2983846e3a9
Reviewed-on: https://pdfium-review.googlesource.com/24650
Commit-Queue: Henrique Nakashima <hnakashima@chromium.org>
Reviewed-by: dsinclair <dsinclair@chromium.org>

1 files changed, 9 insertions, 0 deletions

diff --git a/core/fpdfapi/page/cpdf_streamparser.cpp b/core/fpdfapi/page/cpdf_streamparser.cpp
index 2c7e0256f5..71c8c8d29a 100644
--- a/core/fpdfapi/page/cpdf_streamparser.cpp
+++ b/core/fpdfapi/page/cpdf_streamparser.cpp
@@ -478,6 +478,9 @@ ByteString CPDF_StreamParser::ReadString() {
       case 0:
         if (ch == ')') {
           if (parlevel == 0) {
+            if (buf.tellp() <= 0)
+              return ByteString();
+
             return ByteString(
                 buf.str().c_str(),
                 std::min(static_cast<size_t>(buf.tellp()), kMaxStringLength));
@@ -557,6 +560,9 @@ ByteString CPDF_StreamParser::ReadString() {
   if (PositionIsInBounds())
     ++m_Pos;
 
+  if (buf.tellp() <= 0)
+    return ByteString();
+
   return ByteString(
       buf.str().c_str(),
       std::min(static_cast<size_t>(buf.tellp()), kMaxStringLength));
@@ -590,6 +596,9 @@ ByteString CPDF_StreamParser::ReadHexString() {
   if (!bFirst)
     buf << static_cast<char>(code);
 
+  if (buf.tellp() <= 0)
+    return ByteString();
+
   return ByteString(
       buf.str().c_str(),
       std::min(static_cast<size_t>(buf.tellp()), kMaxStringLength));