From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754538Ab3KGViL (ORCPT ); Thu, 7 Nov 2013 16:38:11 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:49130 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753164Ab3KGViC (ORCPT ); Thu, 7 Nov 2013 16:38:02 -0500 Date: Thu, 7 Nov 2013 13:38:00 -0800 From: Andrew Morton To: Cody P Schafer Cc: EXT4 , Jan Kara , rostedt@goodmis.org, Seth Jennings , LKML Subject: Re: [PATCH v2 01/11] rbtree: Fix rbtree_postorder_for_each_entry_safe() iterator Message-Id: <20131107133800.c779b2f2b2ec73c91cd25f47@linux-foundation.org> In-Reply-To: <1383788572-25938-2-git-send-email-cody@linux.vnet.ibm.com> References: <1383788572-25938-1-git-send-email-cody@linux.vnet.ibm.com> <1383788572-25938-2-git-send-email-cody@linux.vnet.ibm.com> X-Mailer: Sylpheed 3.2.0beta5 (GTK+ 2.24.10; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 6 Nov 2013 17:42:30 -0800 Cody P Schafer wrote: > The iterator rbtree_postorder_for_each_entry_safe() relies on pointer > underflow behavior when testing for loop termination. In particular > it expects that > &rb_entry(NULL, type, field)->field > is NULL. But the result of this expression is not defined by a C standard > and some gcc versions (e.g. 4.3.4) assume the above expression can never > be equal to NULL. The net result is an oops because the iteration is not > properly terminated. > > Fix the problem by modifying the iterator to avoid pointer underflows. So the sole caller is in zswap.c. Is that code actually generating oopses? IOW, is there any need to fix this in 3.12 or earlier?