From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752222AbdK1KMM convert rfc822-to-8bit (ORCPT ); Tue, 28 Nov 2017 05:12:12 -0500 Received: from smtp-out4.electric.net ([192.162.216.195]:58682 "EHLO smtp-out4.electric.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750871AbdK1KMI (ORCPT ); Tue, 28 Nov 2017 05:12:08 -0500 From: David Laight To: "'Eric W. Biederman'" , Linus Torvalds CC: "Tobin C. Harding" , "Jason A. Donenfeld" , "Theodore Ts'o" , Kees Cook , "Paolo Bonzini" , Tycho Andersen , "Roberts, William C" , Tejun Heo , "Jordan Glover" , Greg KH , Petr Mladek , Joe Perches , Ian Campbell , Sergey Senozhatsky , Catalin Marinas , Will Deacon , Steven Rostedt , Chris Fries , Dave Weinstein , Daniel Micay , Djalal Harouni , =?iso-8859-2?Q?Radim_Krcm=E1r?= , "Linux Kernel Mailing List" , KVM list , "kernel-hardening@lists.openwall.com" Subject: RE: [PATCH 0/5] add printk specifier %px, unique identifier Thread-Topic: [PATCH 0/5] add printk specifier %px, unique identifier Thread-Index: AQHTaBIBs5gJiP9r+U2yQsu84EU3hqMpj6ng Date: Tue, 28 Nov 2017 10:12:09 +0000 Message-ID: References: <1511826058-2563-1-git-send-email-me@tobin.cc> <874lpelxzh.fsf@xmission.com> In-Reply-To: <874lpelxzh.fsf@xmission.com> Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.99.200] Content-Type: text/plain; charset="iso-8859-2" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 X-Outbound-IP: 156.67.243.126 X-Env-From: David.Laight@ACULAB.COM X-Proto: esmtps X-Revdns: X-HELO: AcuMS.aculab.com X-TLS: TLSv1.2:ECDHE-RSA-AES256-SHA384:256 X-Authenticated_ID: X-PolicySMART: 3396946, 3397078 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Eric W. Biederman > Sent: 28 November 2017 06:27 > Linus Torvalds writes: > > > On Mon, Nov 27, 2017 at 4:03 PM, Linus Torvalds > > wrote: > >> > >> So the big remaining ones for me are the /proc//stack (stack > >> pointers) and the /proc/net/* ones. > >> > >> I'm a bit disappointed that those haven't been fixed already and > >> aren't even in this series.. > > > > Oh well, I just did /proc//stack by making it just print 0 > > unconditionally rather than the hex number. > > Patch? > > I know I have used /proc//stack manually many times when looking > at a system where something is hung/weird and I needed to see what is > going on. The backtrace inside the kernel can be invaluable. Ditto - after I spotted it. Also the similar tracebacks from echo t >/proc/sysrq-trigger although they are less useful unless you've a big kernel message buffer. Although they can be requested from a keyboard if everything except the keyboard interrupt is borked. > At the same time I don't know if we actually need the hex address. > But please don't break that interface it is very useful. Definitely need to know which addresses are zero (or near zero). I will have tied the addresses there to ones available elsewhere. (In private trace that won't be affected by whatever kernel printf does with %p.) If you want to hide addresses, then maybe use a write-only sysctl. David