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 F016D6B00A6 for ; Sat, 30 May 2009 03:57:10 -0400 (EDT) Message-ID: <4A20E601.9070405@cs.helsinki.fi> Date: Sat, 30 May 2009 10:53:37 +0300 From: Pekka Enberg MIME-Version: 1.0 Subject: Re: [patch 0/5] Support for sanitization flag in low-level page allocator References: <4A15A8C7.2030505@redhat.com> <20090522073436.GA3612@elte.hu> <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> In-Reply-To: <20090530075033.GL29711@oblivion.subreption.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: "Larry H." 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: Hi Larry, On 10:35 Sat 30 May, Pekka Enberg wrote: >> The GFP_SENSITIVE flag looks like a big hammer that we don't really >> need IMHO. It seems to me that most of the actual call-sites (crypto >> code, wireless keys, etc.) should probably just use kzfree() >> unconditionally to make sure we don't leak sensitive data. I did not >> look too closely but I don't think any of the sensitive kfree() calls >> are in fastpaths so the performance impact is negligible. Larry H. 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"? Thanks! Pekka -- 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