ntdll: Catch bad pointers in RtlWow64EnableFsRedirectionEx.

dlls/ntdll/directory.c

@@ -3022,6 +3022,8 @@ NTSTATUS WINAPI RtlWow64EnableFsRedirection( BOOLEAN enable )
 NTSTATUS WINAPI RtlWow64EnableFsRedirectionEx( ULONG disable, ULONG *old_value )
 {
     if (!is_wow64) return STATUS_NOT_IMPLEMENTED;
+    if (((ULONG_PTR)old_value >> 16) == 0) return STATUS_ACCESS_VIOLATION;
+
     *old_value = !ntdll_get_thread_data()->wow64_redir;
     ntdll_get_thread_data()->wow64_redir = !disable;
     return STATUS_SUCCESS;

dlls/ntdll/tests/directory.c

@@ -287,6 +287,11 @@ static void test_redirection(void)
     ok( !status, "RtlWow64EnableFsRedirectionEx failed status %x\n", status );
     ok( !cur, "RtlWow64EnableFsRedirectionEx got %u\n", cur );
 
+    status = pRtlWow64EnableFsRedirectionEx( TRUE, NULL );
+    ok( status == STATUS_ACCESS_VIOLATION, "RtlWow64EnableFsRedirectionEx failed with status %x\n", status );
+    status = pRtlWow64EnableFsRedirectionEx( TRUE, (void*)1 );
+    ok( status == STATUS_ACCESS_VIOLATION, "RtlWow64EnableFsRedirectionEx failed with status %x\n", status );
+
     status = pRtlWow64EnableFsRedirection( FALSE );
     ok( !status, "RtlWow64EnableFsRedirectionEx failed status %x\n", status );
     status = pRtlWow64EnableFsRedirectionEx( FALSE, &cur );