Return the required padding size instead of the current position to avoid integer overflow.

3 files changed, 9 insertions, 17 deletions

diff --git a/src/vm/eventpipeblock.h b/src/vm/eventpipeblock.h
index 78b04af805..c85a84e461 100644
--- a/src/vm/eventpipeblock.h
+++ b/src/vm/eventpipeblock.h
@@ -51,14 +51,13 @@ public:
         if (eventsSize == 0)
             return;
 
-        size_t currentPosition = pSerializer->GetCurrentPosition();
-        if (currentPosition % ALIGNMENT_SIZE != 0)
+        unsigned int requiredPadding = pSerializer->GetRequiredPadding();
+        if (requiredPadding != 0)
         {
             BYTE maxPadding[ALIGNMENT_SIZE - 1] = {}; // it's longest possible padding, we are going to use only part of it
-            unsigned int paddingLength = ALIGNMENT_SIZE - (currentPosition % ALIGNMENT_SIZE);
-            pSerializer->WriteBuffer(maxPadding, paddingLength); // we write zeros here, the reader is going to always read from the first aligned address of the serialized content
+            pSerializer->WriteBuffer(maxPadding, requiredPadding); // we write zeros here, the reader is going to always read from the first aligned address of the serialized content
 
-            _ASSERTE(pSerializer->HasWriteErrors() || (pSerializer->GetCurrentPosition() % ALIGNMENT_SIZE == 0));
+            _ASSERTE(pSerializer->HasWriteErrors() || (pSerializer->GetRequiredPadding() == 0));
         }
 
         pSerializer->WriteBuffer(m_pBlock, eventsSize);
diff --git a/src/vm/fastserializer.cpp b/src/vm/fastserializer.cpp
index 3330bffc2f..73a8da553e 100644
--- a/src/vm/fastserializer.cpp
+++ b/src/vm/fastserializer.cpp
@@ -132,7 +132,7 @@ FastSerializer::FastSerializer(StreamWriter *pStreamWriter) : m_pStreamWriter(pS
     CONTRACTL_END;
 
     m_writeErrorEncountered = false;
-    m_currentPos = 0;
+    m_requiredPadding = 0;
     WriteFileHeader();
 }
 
@@ -190,19 +190,12 @@ void FastSerializer::WriteBuffer(BYTE *pBuffer, unsigned int length)
         uint32_t outCount;
         bool fSuccess = m_pStreamWriter->Write(pBuffer, length, outCount);
 
-#ifdef _DEBUG
-        size_t prevPos = m_currentPos;
-#endif
-        m_currentPos += outCount;
+        m_requiredPadding = (ALIGNMENT_SIZE + m_requiredPadding - (outCount % ALIGNMENT_SIZE)) % ALIGNMENT_SIZE;
 
         // This will cause us to stop writing to the file.
         // The file will still remain open until shutdown so that we don't
         // have to take a lock at this level when we touch the file stream.
         m_writeErrorEncountered = (length != outCount) || !fSuccess;
-
-#ifdef _DEBUG
-        _ASSERTE(m_writeErrorEncountered || (prevPos < m_currentPos));
-#endif
     }
     EX_CATCH
     {
diff --git a/src/vm/fastserializer.h b/src/vm/fastserializer.h
index f62bb62b52..aa0501f0ae 100644
--- a/src/vm/fastserializer.h
+++ b/src/vm/fastserializer.h
@@ -86,10 +86,10 @@ public:
     void WriteTag(FastSerializerTags tag, BYTE *payload = NULL, unsigned int payloadLength = 0);
     void WriteString(const char *strContents, unsigned int length);
 
-    size_t GetCurrentPosition() const
+    unsigned int GetRequiredPadding() const
     {
         LIMITED_METHOD_CONTRACT;
-        return m_currentPos;
+        return m_requiredPadding;
     }
 
     bool HasWriteErrors() const
@@ -104,7 +104,7 @@ private:
 
     StreamWriter *const m_pStreamWriter;
     bool m_writeErrorEncountered;
-    size_t m_currentPos;
+    unsigned int m_requiredPadding;
 };
 
 #endif // FEATURE_PERFTRACING