From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail203.messagelabs.com (mail203.messagelabs.com [216.82.254.243]) by kanga.kvack.org (Postfix) with ESMTP id CEE4D6B00AD for ; Sat, 30 May 2009 04:22:47 -0400 (EDT) Date: Sat, 30 May 2009 01:20:48 -0700 From: "Larry H." Subject: Re: [patch 0/5] Support for sanitization flag in low-level page allocator Message-ID: <20090530082048.GM29711@oblivion.subreption.com> References: <20090522113809.GB13971@oblivion.subreption.com> <20090523124944.GA23042@elte.hu> <4A187BDE.5070601@redhat.com> <20090527223421.GA9503@elte.hu> <20090528072702.796622b6@lxorguk.ukuu.org.uk> <20090528090836.GB6715@elte.hu> <20090528125042.28c2676f@lxorguk.ukuu.org.uk> <84144f020905300035g1d5461f9n9863d4dcdb6adac0@mail.gmail.com> <20090530075033.GL29711@oblivion.subreption.com> <4A20E601.9070405@cs.helsinki.fi> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4A20E601.9070405@cs.helsinki.fi> Sender: owner-linux-mm@kvack.org To: Pekka Enberg Cc: Alan Cox , Ingo Molnar , Rik van Riel , linux-kernel@vger.kernel.org, Linus Torvalds , linux-mm@kvack.org, Ingo Molnar , pageexec@freemail.hu, Linus Torvalds List-ID: On 10:53 Sat 30 May , Pekka Enberg wrote: >> That's hopeless, and kzfree is broken. Like I said in my earlier reply, >> please test that yourself to see the results. Whoever wrote that ignored >> how SLAB/SLUB work and if kzfree had been used somewhere in the kernel >> before, it should have been noticed long time ago. > > An open-coded version of kzfree was being used in the kernel: > > http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=00fcf2cb6f6bb421851c3ba062c0a36760ea6e53 > > Can we now get to the part where you explain how it's broken because I > obviously "ignored how SLAB/SLUB works"? You can find the answer in the code of sanitize_obj, within my kfree patch. Besides, it would have taken less time for you to write a simple module that kmallocs and kzfrees a buffer, than writing these two emails. Consider the inuse, size, objsize and offset members of a kmem_cache structure, for further hints. Test the module on a system with SLUB, though the issue should replicate over SLAB too. And don't dare test it on SLOB and its wonderful ksize, or even look at the freelist pointer management within SLUB. ;) I'm about to recommend Andrew to take a look at this too: http://marc.info/?l=linux-mm&m=124301548814293&w=2 Larry -- 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