diff --git a/reactos/subsys/win32k/include/mmcopy.h b/reactos/subsys/win32k/include/mmcopy.h
index c779ead8b25..b917696622a 100644
--- a/reactos/subsys/win32k/include/mmcopy.h
+++ b/reactos/subsys/win32k/include/mmcopy.h
@@ -4,8 +4,9 @@
 #include <pseh/pseh.h>
 
 NTSTATUS _MmCopyFromCaller( PVOID Target, PVOID Source, UINT Bytes );
+NTSTATUS _MmCopyToCaller( PVOID Target, PVOID Source, UINT Bytes );
 
 #define MmCopyFromCaller(x,y,z) _MmCopyFromCaller((PCHAR)(x),(PCHAR)(y),(UINT)(z))
-#define MmCopyToCaller(x,y,z) MmCopyFromCaller(x,y,z)
+#define MmCopyToCaller(x,y,z) _MmCopyToCaller((PCHAR)(x),(PCHAR)(y),(UINT)(z))
 
 #endif/*NDK_MMCOPY_H*/
diff --git a/reactos/subsys/win32k/misc/copy.c b/reactos/subsys/win32k/misc/copy.c
index 3de5a355d73..288c2dcc7d6 100644
--- a/reactos/subsys/win32k/misc/copy.c
+++ b/reactos/subsys/win32k/misc/copy.c
@@ -2,9 +2,23 @@
 
 NTSTATUS _MmCopyFromCaller( PVOID Target, PVOID Source, UINT Bytes ) {
     NTSTATUS Status = STATUS_SUCCESS;
-
+    
     _SEH_TRY {
-	RtlCopyMemory(Target,Source,Bytes);
+        ProbeForRead(Source,Bytes,1);
+        RtlCopyMemory(Target,Source,Bytes);
+    } _SEH_HANDLE {
+	Status = _SEH_GetExceptionCode();
+    } _SEH_END;
+
+    return Status;
+}
+
+NTSTATUS _MmCopyToCaller( PVOID Target, PVOID Source, UINT Bytes ) {
+    NTSTATUS Status = STATUS_SUCCESS;
+    
+    _SEH_TRY {
+        ProbeForWrite(Target,Bytes,1);
+        RtlCopyMemory(Target,Source,Bytes);
     } _SEH_HANDLE {
 	Status = _SEH_GetExceptionCode();
     } _SEH_END;