From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f70.google.com (mail-pg0-f70.google.com [74.125.83.70]) by kanga.kvack.org (Postfix) with ESMTP id 42A73440D03 for ; Thu, 9 Nov 2017 20:05:23 -0500 (EST) Received: by mail-pg0-f70.google.com with SMTP id q126so7098810pgq.7 for ; Thu, 09 Nov 2017 17:05:23 -0800 (PST) Received: from mail.kernel.org (mail.kernel.org. [198.145.29.99]) by mx.google.com with ESMTPS id 73si8015877pfr.339.2017.11.09.17.05.22 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 09 Nov 2017 17:05:22 -0800 (PST) Received: from mail-io0-f178.google.com (mail-io0-f178.google.com [209.85.223.178]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id EB6F221992 for ; Fri, 10 Nov 2017 01:05:19 +0000 (UTC) Received: by mail-io0-f178.google.com with SMTP id n137so11878447iod.6 for ; Thu, 09 Nov 2017 17:05:19 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <27b55108-1e72-cb3d-d5d8-ffe0238245aa@linux.intel.com> References: <20171108194646.907A1942@viggo.jf.intel.com> <20171108194731.AB5BDA01@viggo.jf.intel.com> <6871f284-b7e9-f843-608f-5345f9d03396@linux.intel.com> <27b55108-1e72-cb3d-d5d8-ffe0238245aa@linux.intel.com> From: Andy Lutomirski Date: Thu, 9 Nov 2017 17:04:58 -0800 Message-ID: Subject: Re: [PATCH 24/30] x86, kaiser: disable native VSYSCALL Content-Type: text/plain; charset="UTF-8" Sender: owner-linux-mm@kvack.org List-ID: To: Dave Hansen Cc: Andy Lutomirski , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , moritz.lipp@iaik.tugraz.at, Daniel Gruss , michael.schwarz@iaik.tugraz.at, richard.fellner@student.tugraz.at, Linus Torvalds , Kees Cook , Hugh Dickins , X86 ML On Thu, Nov 9, 2017 at 4:57 PM, Dave Hansen wrote: > On 11/09/2017 04:53 PM, Andy Lutomirski wrote: >>> The KAISER code attempts to "poison" the user portion of the kernel page >>> tables. It detects the entries pages that it wants that it wants to >>> poison in two ways: >>> * Looking for addresses >= PAGE_OFFSET >>> * Looking for entries without _PAGE_USER set >> What do you mean "poison"? > > I meant the _PAGE_NX magic that we do in here: > > https://git.kernel.org/pub/scm/linux/kernel/git/daveh/x86-kaiser.git/commit/?h=kaiser-414rc7-20171108&id=c4f7d0819170761f092fcf2327b85b082368e73a > > to ensure that userspace is unable to run on the kernel PGD. Aha, I get it. Why not just drop the _PAGE_USER check? You could instead warn if you see a _PAGE_USER page that doesn't have the correct address for the vsyscall. -- 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