From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-yw0-f199.google.com (mail-yw0-f199.google.com [209.85.161.199]) by kanga.kvack.org (Postfix) with ESMTP id A9F846B0320 for ; Tue, 12 Sep 2017 03:11:08 -0400 (EDT) Received: by mail-yw0-f199.google.com with SMTP id v137so13982192ywg.4 for ; Tue, 12 Sep 2017 00:11:08 -0700 (PDT) Received: from szxga05-in.huawei.com (szxga05-in.huawei.com. [45.249.212.191]) by mx.google.com with ESMTPS id k39si2230223ybj.367.2017.09.12.00.11.06 for (version=TLS1 cipher=AES128-SHA bits=128/128); Tue, 12 Sep 2017 00:11:07 -0700 (PDT) Subject: Re: [PATCH v6 00/11] Add support for eXclusive Page Frame Ownership References: <20170907173609.22696-1-tycho@docker.com> <23e5bac9-329a-3a32-049e-7e7c9751abd0@huawei.com> <20170911150204.nn5v5olbxyzfafou@docker> From: Yisheng Xie Message-ID: <60c4ad22-d920-2754-30dd-b1f228c0a87d@huawei.com> Date: Tue, 12 Sep 2017 15:07:29 +0800 MIME-Version: 1.0 In-Reply-To: <20170911150204.nn5v5olbxyzfafou@docker> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Tycho Andersen Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, kernel-hardening@lists.openwall.com, Marco Benatto , Juerg Haefliger Hi Tycho, On 2017/9/11 23:02, Tycho Andersen wrote: > Hi Yisheng, > > On Mon, Sep 11, 2017 at 06:34:45PM +0800, Yisheng Xie wrote: >> Hi Tycho , >> >> On 2017/9/8 1:35, Tycho Andersen wrote: >>> Hi all, >>> >>> Here is v6 of the XPFO set; see v5 discussion here: >>> https://lkml.org/lkml/2017/8/9/803 >>> >>> Changelogs are in the individual patch notes, but the highlights are: >>> * add primitives for ensuring memory areas are mapped (although these are quite >>> ugly, using stack allocation; I'm open to better suggestions) >>> * instead of not flushing caches, re-map pages using the above >>> * TLB flushing is much more correct (i.e. we're always flushing everything >>> everywhere). I suspect we may be able to back this off in some cases, but I'm >>> still trying to collect performance numbers to prove this is worth doing. >>> >>> I have no TODOs left for this set myself, other than fixing whatever review >>> feedback people have. Thoughts and testing welcome! >> >> According to the paper of Vasileios P. Kemerlis et al, the mainline kernel >> will not set the Pro. of physmap(direct map area) to RW(X), so do we really >> need XPFO to protect from ret2dir attack? > > I guess you're talking about section 4.3? Yes > They mention that that x86 > only gets rw, but that aarch64 is rwx still. IIRC, the in kernel of v4.13 the aarch64 is not rwx, I will check it. > > But in either case this still provides access protection, similar to > SMAP. Also, if I understand things correctly the protections are > unmanaged, so a page that had the +x bit set at some point, it could > be used for ret2dir. So you means that the Pro. of direct map area maybe changed to +x, then ret2dir attack can use it? Thanks Yisheng Xie -- 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