iobuffer memstomp fix (#85)

* Don't try to validate empty compact binary
* Don't try to free fake memory buffer pointer in iobuffer destructor

3 files changed, 16 insertions, 3 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 5dc0050f3..93ea90d45 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,8 @@
 ##
 - Bugfix: If we get a request for a partial chunk that can not be fulfilled we warn and treat it as a miss
 - Bugfix: Correctly calculate memory view size from Mid/MidInline function if size is not given
+- Bugfix: Don't try to read bytes to validate a compact binary object that is empty
+- Bugfix: Don't fake free memory buffer pointer when materializing a zero size file
 - Improvement: Asserts gives an immediate ERROR log entry with callstack and reason
 - Improvement: Asserts flushes the log before sending error report to Sentry
 - Improvement: Refactored IterateChunks to allow reuse in diskcachelayer and hide public GetBlockFile() function in BlockStore
diff --git a/src/zencore/compactbinaryvalidation.cpp b/src/zencore/compactbinaryvalidation.cpp
index 462978f63..db830d250 100644
--- a/src/zencore/compactbinaryvalidation.cpp
+++ b/src/zencore/compactbinaryvalidation.cpp
@@ -544,10 +544,17 @@ ValidateCompactBinary(MemoryView View, CbValidateMode Mode, CbFieldType Type)
 	CbValidateError Error = CbValidateError::None;
 	if (EnumHasAnyFlags(Mode, CbValidateMode::All))
 	{
-		ValidateCbField(View, Mode, Error, Type);
-		if (!View.IsEmpty() && EnumHasAnyFlags(Mode, CbValidateMode::Padding))
+		if (View.IsEmpty())
 		{
-			AddError(Error, CbValidateError::Padding);
+			AddError(Error, CbValidateError::OutOfBounds);
+		}
+		else
+		{
+			ValidateCbField(View, Mode, Error, Type);
+			if (!View.IsEmpty() && EnumHasAnyFlags(Mode, CbValidateMode::Padding))
+			{
+				AddError(Error, CbValidateError::Padding);
+			}
 		}
 	}
 	return Error;
diff --git a/src/zencore/iobuffer.cpp b/src/zencore/iobuffer.cpp
index e1e8750a1..fd99a01cb 100644
--- a/src/zencore/iobuffer.cpp
+++ b/src/zencore/iobuffer.cpp
@@ -212,6 +212,10 @@ IoBufferExtendedCore::~IoBufferExtendedCore()
 
 		m_DataPtr = nullptr;  // prevent any buffer deallocation attempts
 	}
+	else if (m_DataPtr == reinterpret_cast<uint8_t*>(&m_MmapHandle))
+	{
+		m_DataPtr = nullptr;
+	}
 
 	const uint32_t LocalFlags = m_Flags.load(std::memory_order_relaxed);
 #if ZEN_PLATFORM_WINDOWS