From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f197.google.com (mail-wr0-f197.google.com [209.85.128.197]) by kanga.kvack.org (Postfix) with ESMTP id A6A206B0008 for ; Tue, 20 Feb 2018 12:17:04 -0500 (EST) Received: by mail-wr0-f197.google.com with SMTP id c37so4106501wra.5 for ; Tue, 20 Feb 2018 09:17:04 -0800 (PST) Received: from huawei.com (lhrrgout.huawei.com. [194.213.3.17]) by mx.google.com with ESMTPS id m187si15889469wmg.35.2018.02.20.09.17.03 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 20 Feb 2018 09:17:03 -0800 (PST) Subject: Re: [kernel-hardening] [PATCH 4/6] Protectable Memory References: <20180124175631.22925-1-igor.stoppa@huawei.com> <20180124175631.22925-5-igor.stoppa@huawei.com> <20180126053542.GA30189@bombadil.infradead.org> <8818bfd4-dd9f-f279-0432-69b59531bd41@huawei.com> <17e5b515-84c8-dca2-1695-cdf819834ea2@huawei.com> <414027d3-dd73-cf11-dc2a-e8c124591646@redhat.com> <5a83024c.64369d0a.a1e94.cdd6SMTPIN_ADDED_BROKEN@mx.google.com> <13a50f85-bbd8-5d78-915a-a29c4a9f0c32@redhat.com> From: Igor Stoppa Message-ID: <7972cf4d-dfb2-6682-b1cb-e514a41196a6@huawei.com> Date: Tue, 20 Feb 2018 19:16:38 +0200 MIME-Version: 1.0 In-Reply-To: <13a50f85-bbd8-5d78-915a-a29c4a9f0c32@redhat.com> Content-Type: text/plain; charset="gbk" Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Laura Abbott , Kees Cook Cc: Boris Lukashev , Christopher Lameter , Matthew Wilcox , Jann Horn , Jerome Glisse , Michal Hocko , Christoph Hellwig , linux-security-module , Linux-MM , kernel list , Kernel Hardening On 13/02/18 20:10, Laura Abbott wrote: > On 02/13/2018 07:20 AM, Igor Stoppa wrote: >> Why alterations of page properties are not considered a risk and the physmap is? >> And how would it be easier (i suppose) to attack the latter? > > Alterations are certainly a risk but with the physmap the > mapping is already there. Find the address and you have > access vs. needing to actually modify the properties > then do the access. I could also be complete off base > on my threat model here so please correct me if I'm > wrong. It's difficult for me to comment on this without knowing *how* the attack would be performed, in your model. Ex: my expectation is that the attacked has R/W access to kernel data and has knowledge of the location of static variables. This is not just a guess, but a real-life scenario, found in attacks that, among other things, are capable of disabling SELinux, to proceed toward gaining full root capability. At that point, I think that variables which are allocated dynamically, in vmalloc address space, are harder to locate, because of the virtual mapping and the randomness of the address chosen (this I have not confirmed yet, but I suppose there is some randomness in picking the address to assign to a certain allocation request to vmalloc, otherwise, it could be added). > I think your other summaries are good points though > and should go in the cover letter. Ok, I'm just afraid it risks becoming a lengthy dissertation :-) -- igor -- 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