From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with ESMTP id A944B6B0207 for ; Wed, 24 Mar 2010 17:28:58 -0400 (EDT) Date: Wed, 24 Mar 2010 15:28:54 -0600 From: Jonathan Corbet Subject: Re: [PATCH 07/11] Memory compaction core Message-ID: <20100324152854.48f72171@bike.lwn.net> In-Reply-To: <20100324211924.GH10659@random.random> References: <1269347146-7461-1-git-send-email-mel@csn.ul.ie> <1269347146-7461-8-git-send-email-mel@csn.ul.ie> <20100324133347.9b4b2789.akpm@linux-foundation.org> <20100324145946.372f3f31@bike.lwn.net> <20100324211924.GH10659@random.random> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org To: Andrea Arcangeli Cc: Andrew Morton , Mel Gorman , Christoph Lameter , Adam Litke , Avi Kivity , David Rientjes , Minchan Kim , KAMEZAWA Hiroyuki , KOSAKI Motohiro , Rik van Riel , linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: On Wed, 24 Mar 2010 22:19:24 +0100 Andrea Arcangeli wrote: > > > It's a bit strange to test this when we're about to oops anyway. The > > > oops will tell us the same thing. > > > > ...except that we've seen a fair number of null pointer dereference > > exploits that have told us something altogether different. Are we > > *sure* we don't want to test for null pointers...? > > Examples? Maybe WARN_ON != oops, but VM_BUG_ON still an oops that is > and without serial console it would go lost too. I personally don't > see how it's needed. I don't quite understand the question; are you asking for examples of exploits? http://lwn.net/Articles/347006/ http://lwn.net/Articles/360328/ http://lwn.net/Articles/342330/ ... As to whether this particular test makes sense, I don't know. But the idea that we never need to test about-to-be-dereferenced pointers for NULL does worry me a bit. jon -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org