Index: reactos/win32ss/user/ntuser/class.c
===================================================================
--- reactos/win32ss/user/ntuser/class.c	(revision 72796)
+++ reactos/win32ss/user/ntuser/class.c	(working copy)
@@ -334,31 +334,47 @@
 IntRegisterClassAtom(IN PUNICODE_STRING ClassName,
                      OUT RTL_ATOM *pAtom)
 {
-    WCHAR szBuf[65];
+    NTSTATUS Status;
+    DWORD Size;
     PWSTR AtomName;
-    NTSTATUS Status;
+    PWSTR Allocated = NULL;
 
-    if (ClassName->Length != 0)
+    _SEH2_TRY
     {
-        /* FIXME: Don't limit to 64 characters! Use SEH when allocating memory! */
-        if (ClassName->Length / sizeof(WCHAR) >= sizeof(szBuf) / sizeof(szBuf[0]))
+        if (ClassName->Length != 0)
         {
-            EngSetLastError(ERROR_INVALID_PARAMETER);
-            return (RTL_ATOM)0;
+            /* allocate a buffer */
+            Size = ClassName->Length + sizeof(WCHAR);
+            Allocated = UserHeapAlloc(Size);
+            if (!Allocated)
+            {
+                _SEH2_YIELD(return STATUS_INSUFFICIENT_RESOURCES);
+            }
+
+            /* store string */
+            RtlCopyMemory(Allocated, ClassName->Buffer, ClassName->Length);
+            Allocated[ClassName->Length / sizeof(WCHAR)] = UNICODE_NULL;
+            AtomName = Allocated;
         }
+        else
+        {
+            AtomName = ClassName->Buffer;
+        }
 
-        RtlCopyMemory(szBuf,
-                      ClassName->Buffer,
-                      ClassName->Length);
-        szBuf[ClassName->Length / sizeof(WCHAR)] = UNICODE_NULL;
-        AtomName = szBuf;
+        /* add atom */
+        Status = RtlAddAtomToAtomTable(gAtomTable, AtomName, pAtom);
     }
-    else
-        AtomName = ClassName->Buffer;
+    _SEH2_EXCEPT(EXCEPTION_EXECUTE_HANDLER)
+    {
+        Status = _SEH2_GetExceptionCode();
+    }
+    _SEH2_END;
 
-    Status = RtlAddAtomToAtomTable(gAtomTable,
-                                   AtomName,
-                                   pAtom);
+    /* free the buffer */
+    if (Allocated)
+    {
+        UserHeapFree(Allocated);
+    }
 
     if (!NT_SUCCESS(Status))
     {
@@ -1270,43 +1286,35 @@
     _Out_ RTL_ATOM *Atom)
 {
     BOOL Ret = FALSE;
+    PWSTR Allocated;
+    NTSTATUS Status;
+    DWORD Size;
 
-    if (ClassName->Length != 0)
+    if (ClassName->Length == 0)
     {
-        WCHAR szBuf[65];
-        PWSTR AtomName;
-        NTSTATUS Status;
+        ASSERT(IS_ATOM(ClassName->Buffer));
+        *Atom = (RTL_ATOM)((ULONG_PTR)ClassName->Buffer);
+        return TRUE;
+    }
 
-        *Atom = 0;
+    *Atom = 0;
 
-        /* NOTE: Caller has to protect the call with SEH! */
-
-        if (ClassName->Length != 0)
+    _SEH2_TRY
+    {
+        /* allocate a buffer */
+        Size = ClassName->Length + sizeof(WCHAR);
+        Allocated = UserHeapAlloc(Size);
+        if (!Allocated)
         {
-            /* FIXME: Don't limit to 64 characters! use SEH when allocating memory! */
-            if (ClassName->Length / sizeof(WCHAR) >= sizeof(szBuf) / sizeof(szBuf[0]))
-            {
-                EngSetLastError(ERROR_INVALID_PARAMETER);
-                return (RTL_ATOM)0;
-            }
-
-            /* We need to make a local copy of the class name! The caller could
-               modify the buffer and we could overflow in RtlLookupAtomInAtomTable.
-               We're protected by SEH, but the ranges that might be accessed were
-               not probed... */
-            RtlCopyMemory(szBuf,
-                          ClassName->Buffer,
-                          ClassName->Length);
-            szBuf[ClassName->Length / sizeof(WCHAR)] = UNICODE_NULL;
-            AtomName = szBuf;
+            _SEH2_YIELD(return STATUS_INSUFFICIENT_RESOURCES);
         }
-        else
-            AtomName = ClassName->Buffer;
 
+        /* store string */
+        RtlCopyMemory(Allocated, ClassName->Buffer, ClassName->Length);
+        Allocated[ClassName->Length / sizeof(WCHAR)] = UNICODE_NULL;
+
         /* Lookup the atom */
-        Status = RtlLookupAtomInAtomTable(gAtomTable,
-                                          AtomName,
-                                          Atom);
+        Status = RtlLookupAtomInAtomTable(gAtomTable, Allocated, Atom);
         if (NT_SUCCESS(Status))
         {
             Ret = TRUE;
@@ -1319,13 +1327,18 @@
             }
         }
     }
-    else
+    _SEH2_EXCEPT(EXCEPTION_EXECUTE_HANDLER)
     {
-        ASSERT(IS_ATOM(ClassName->Buffer));
-        *Atom = (RTL_ATOM)((ULONG_PTR)ClassName->Buffer);
-        Ret = TRUE;
+        Status = _SEH2_GetExceptionCode();
     }
+    _SEH2_END;
 
+    /* free the buffer */
+    if (Allocated)
+    {
+        UserHeapFree(Allocated);
+    }
+
     return Ret;
 }