From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail138.messagelabs.com (mail138.messagelabs.com [216.82.249.35]) by kanga.kvack.org (Postfix) with ESMTP id 56C0B6B004F for ; Sun, 31 May 2009 07:56:02 -0400 (EDT) Date: Sun, 31 May 2009 04:58:28 -0700 From: "Larry H." Subject: Re: [patch 0/5] Support for sanitization flag in low-level page allocator Message-ID: <20090531115828.GB10598@oblivion.subreption.com> References: <20090530082048.GM29711@oblivion.subreption.com> <20090530173428.GA20013@elte.hu> <20090530180333.GH6535@oblivion.subreption.com> <20090530182113.GA25237@elte.hu> <20090530184534.GJ6535@oblivion.subreption.com> <20090530190828.GA31199@elte.hu> <4A21999E.5050606@redhat.com> <84144f020905301353y2f8c232na4c5f9dfb740eec4@mail.gmail.com> <20090530213311.GM6535@oblivion.subreption.com> <84144f020905310017o3c2b8c52s7d62187cf794e854@mail.gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <84144f020905310017o3c2b8c52s7d62187cf794e854@mail.gmail.com> Sender: owner-linux-mm@kvack.org To: Pekka Enberg Cc: Rik van Riel , Ingo Molnar , Alan Cox , linux-kernel@vger.kernel.org, Linus Torvalds , linux-mm@kvack.org, Ingo Molnar , pageexec@freemail.hu, Linus Torvalds List-ID: On 10:17 Sun 31 May , Pekka Enberg wrote: > On Sun, May 31, 2009 at 12:33 AM, Larry H. wrote: > > While we are at it, did any of you (Pekka, Ingo, Peter) bother reading > > the very first paper I referenced in the very first patch?: > > > > http://www.stanford.edu/~blp/papers/shredding.html/#kernel-appendix > > > > Could you _please_ bother your highness with an earthly five minutes > > read of that paper? If you don't have other magnificent obligations to > > attend to. _Please_. > > > > PS: I'm still thanking myself for not implementing the kthread / > > multiple page pool based approach. Lord, what could have happened if I > > did. > > Something like that might make sense for fast-path code. > > I think we could make GFP_SENSITIVE mean that allocations using it > force the actual slab pages to be cleaned up before they're returned > to the page allocator. As far as I can tell, we could then recycle > those slab pages to GFP_SENSITIVE allocations without any clearing > whatsoever as long as they're managed by slab. This ensures critical > data in kmalloc()'d memory is never leaked to userspace. > > This doesn't fix all the cases Alan pointed out (unconditional > memset() in page free is clearly superior from security pov) but > should allow us to use GFP_SENSITIVE in fast-path cases where the > overhead of kzfree() is unacceptable. Thanks for coming to the conclusion that unconditional memory sanitization is the correct approach. I thought this had been stated numerous times before in this thread. Are you serious about your responses or you are just clowning around? It's amusing, I give you that much. -- 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