[PORTCLS] Zero memory in operator new. CORE-16157

Fixes a regression from 99fa38809f, which
replaced the kcom.h/stdunk.h versions (which zero memory) with local
implementations (which don't).

Standard C++ does not guarantee that memory is zeroed but several classes
rely on this, in particular for their m_Ref and m_bInitialized members.

Ideally the constructors should be fixed to initialize all required members,
but that task is error-prone so for now we simply restore the previous
behavior.

drivers/wdm/audio/backpln/portcls/dma_slave.cpp

@@ -24,7 +24,10 @@ public:
         POOL_TYPE PoolType,
         ULONG Tag)
     {
-        return ExAllocatePoolWithTag(PoolType, Size, Tag);
+        PVOID P = ExAllocatePoolWithTag(PoolType, Size, Tag);
+        if (P)
+            RtlZeroMemory(P, Size);
+        return P;
     }
 
     STDMETHODIMP QueryInterface( REFIID InterfaceId, PVOID* Interface);

drivers/wdm/audio/backpln/portcls/miniport.cpp

@@ -21,7 +21,10 @@ operator new(
     POOL_TYPE PoolType,
     ULONG Tag)
 {
-    return ExAllocatePoolWithTag(PoolType, Size, Tag);
+    PVOID P = ExAllocatePoolWithTag(PoolType, Size, Tag);
+    if (P)
+        RtlZeroMemory(P, Size);
+    return P;
 }
 
 void

drivers/wdm/audio/backpln/portcls/pin_wavecyclic.cpp

@@ -25,7 +25,10 @@ public:
         POOL_TYPE PoolType,
         ULONG Tag)
     {
-        return ExAllocatePoolWithTag(PoolType, Size, Tag);
+        PVOID P = ExAllocatePoolWithTag(PoolType, Size, Tag);
+        if (P)
+            RtlZeroMemory(P, Size);
+        return P;
     }
 
     STDMETHODIMP QueryInterface( REFIID InterfaceId, PVOID* Interface);