From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751799AbdCADxj (ORCPT ); Tue, 28 Feb 2017 22:53:39 -0500 Received: from foss.arm.com ([217.140.101.70]:44676 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751743AbdCADwL (ORCPT ); Tue, 28 Feb 2017 22:52:11 -0500 Date: Wed, 1 Mar 2017 03:52:15 +0000 From: Will Deacon To: Laura Abbott Cc: Mark Rutland , Ard Biesheuvel , Miles Chen , Catalin Marinas , linux-mediatek@lists.infradead.org, "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , wsd_upstream@mediatek.com Subject: Re: [PATCH] arm64: dump: hide kernel pointers Message-ID: <20170301035214.GA12637@arm.com> References: <1488265536-20441-1-git-send-email-miles.chen@mediatek.com> <20170228100420.GA3691@leverpostej> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Feb 28, 2017 at 02:55:51PM -0800, Laura Abbott wrote: > On 02/28/2017 02:04 AM, Mark Rutland wrote: > > On Tue, Feb 28, 2017 at 08:42:51AM +0000, Ard Biesheuvel wrote: > >> On 28 February 2017 at 07:05, Miles Chen wrote: > >>> Mask kernel pointers of /sys/kernel/debug/kernel_page_tables entry like > >>> /proc/vmallocinfo does. > >>> > >>> With sysctl kernel.kptr_restrict=0 or 1: > >>> cat /sys/kernel/debug/kernel_page_tables > >> > >> I wonder if this file should be accessible at all if kptr_restrict > 0 > > > > I don't have strong feelings either way. > > > > This isn't typically enabled, and it's under debugfs, so this shouldn't > > be accessible by a typical user anyhow. > > > > That said, there are very few of us who need to take a look at this > > file. I'm happy to deal with attacking kptr_restrict when required. > > > > In the interest of security it's probably for the best to switch to the > restricted pointer. Who knows what might get enabled or forgotten about. > I don't like the idea of tying enablement of the file to kptr_restrict > though. ... but it's also pretty weird to show the sizes, mapping type and permissions yet hide the virtual addresses. If you want to keep the file in spite of kptr_restrict, which bits are actually useful once the addresses are nobbled? Will