Fix potential null pointer dereference

Calling WriteFile with both lpOverlapped and lpNumberOfBytesWritten set to null is invalid combination on Windows 7

[tfs-changeset: 1472978]

2 files changed, 8 insertions, 1 deletions

diff --git a/src/zap/zapimage.cpp b/src/zap/zapimage.cpp
index a7723c74d0..09e2b4dd9d 100644
--- a/src/zap/zapimage.cpp
+++ b/src/zap/zapimage.cpp
@@ -914,6 +914,10 @@ public:
 
         m_hasher.HashMore(pv, cb);
 
+        // We are calling with lpOverlapped == NULL so pcbWritten has to be present
+        // to prevent crashes in Win7 and below.
+        _ASSERTE(pcbWritten);
+
         if (!::WriteFile(m_hFile, pv, cb, pcbWritten, NULL))
         {
             hr = HRESULT_FROM_GetLastError();
diff --git a/src/zap/zapwriter.cpp b/src/zap/zapwriter.cpp
index 2cd784b271..357aebdd32 100644
--- a/src/zap/zapwriter.cpp
+++ b/src/zap/zapwriter.cpp
@@ -388,8 +388,11 @@ void ZapWriter::WritePad(DWORD dwSize, BYTE fill)
 
     while (dwSize >= WRITE_BUFFER_SIZE)
     {
+        ULONG cbWritten;
         cbAvailable = min(WRITE_BUFFER_SIZE, dwSize);
-        IfFailThrow(m_pStream->Write(m_pBuffer, cbAvailable, NULL));
+        IfFailThrow(m_pStream->Write(m_pBuffer, cbAvailable, &cbWritten));
+        _ASSERTE(cbWritten == cbAvailable);
+
         dwSize -= cbAvailable;
     }