From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1AFC1C433DB for ; Thu, 4 Feb 2021 22:57:58 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 4C0A464FAC for ; Thu, 4 Feb 2021 22:57:57 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4C0A464FAC Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=ucw.cz Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 9B9346B0006; Thu, 4 Feb 2021 17:57:56 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 9440E6B006C; Thu, 4 Feb 2021 17:57:56 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 80A4C6B006E; Thu, 4 Feb 2021 17:57:56 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0035.hostedemail.com [216.40.44.35]) by kanga.kvack.org (Postfix) with ESMTP id 680556B0006 for ; Thu, 4 Feb 2021 17:57:56 -0500 (EST) Received: from smtpin04.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 307CF8249980 for ; Thu, 4 Feb 2021 22:57:56 +0000 (UTC) X-FDA: 77782099752.04.boot92_3703625275df Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin04.hostedemail.com (Postfix) with ESMTP id 177C580104C5 for ; Thu, 4 Feb 2021 22:57:56 +0000 (UTC) X-HE-Tag: boot92_3703625275df X-Filterd-Recvd-Size: 4413 Received: from jabberwock.ucw.cz (jabberwock.ucw.cz [46.255.230.98]) by imf41.hostedemail.com (Postfix) with ESMTP for ; Thu, 4 Feb 2021 22:57:55 +0000 (UTC) Received: by jabberwock.ucw.cz (Postfix, from userid 1017) id 5CC6E1C0B77; Thu, 4 Feb 2021 23:57:52 +0100 (CET) Date: Thu, 4 Feb 2021 23:57:51 +0100 From: Pavel Machek To: Kees Cook Cc: Timur Tabi , Steven Rostedt , Petr Mladek , Sergey Senozhatsky , linux-kernel@vger.kernel.org, linux-mm@kvack.org, willy@infradead.org, akpm@linux-foundation.org, torvalds@linux-foundation.org, roman.fietze@magna.com, john.ogness@linutronix.de, akinobu.mita@gmail.com Subject: Re: [PATCH] lib/vsprintf: make-printk-non-secret printks all addresses as unhashed Message-ID: <20210204225751.GD13103@amd> References: <20210202201846.716915-1-timur@kernel.org> <20210204204835.GA7529@amd> <20210204155423.2864bf4f@gandalf.local.home> <20210204214944.GA13103@amd> <873d7e08-7a70-a1a3-f486-882d1d515965@kernel.org> <20210204221143.GB13103@amd> <202102041415.D9093ED6@keescook> <20210204225136.GC13103@amd> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="FFoLq8A0u+X9iRU8" Content-Disposition: inline In-Reply-To: <20210204225136.GC13103@amd> User-Agent: Mutt/1.5.23 (2014-03-12) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: --FFoLq8A0u+X9iRU8 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu 2021-02-04 23:51:36, Pavel Machek wrote: > On Thu 2021-02-04 14:17:13, Kees Cook wrote: > > On Thu, Feb 04, 2021 at 11:11:43PM +0100, Pavel Machek wrote: > > > On Thu 2021-02-04 15:59:21, Timur Tabi wrote: > > > > On 2/4/21 3:49 PM, Pavel Machek wrote: > > > > >This machine is insecure. Yet I don't see ascii-art *** all around= =2E. > > > > > > > > > >"Kernel memory addresses are exposed, which is bad for security." > > > >=20 > > > > I'll use whatever wording everyone can agree on, but I really don't= see much > > > > difference between "which may compromise security on your system" a= nd "which > > > > is bad for security". "may compromise" doesn't see any more alarmi= st than > > > > "bad". Frankly, "bad" is a very generic term. > > >=20 > > > Well, I agree that "bad" is vague.... but original wording is simply > > > untrue, as printing addresses decreases robustness but can't introduce > > > security problem on its own. > > >=20 > > > Being alarmist is not my complaint; being untrue is. > >=20 > > It's just semantics. Printing addresses DOES weaken the security of a > > system, especially when we know attackers have and do use stuff from dm= esg > > to tune their attacks. How about "reduces the security of your system"? >=20 > "reduces" sounds okay to me. >=20 > You should not have attackers on your system. That reduces your security. >=20 > You should not have users reading dmesg. Again that reduces your > security. >=20 > You should not have bugs in your kernel. That reduces your security. Oh, and you really should not run modern, out-of-order CPU. That significantly reduces your security. Yet we have documentation stating that my machine is secure: The Linux kernel contains a mitigation for this attack vector, PTE inversion, which is permanently enabled and has no performance impact. The kernel ensures that the address bits of PTEs, which are not marked present, never point to cacheable physical memory space. A system with an up to date kernel is protected against attacks from malicious user space applications. when it is not: [ 0.545064] L1TF: System has more than MAX_PA/2 memory. L1TF mitigation not effective. [ 0.545163] L1TF: You may make it effective by booting the kernel with mem=3D2147483648 parameter. Best regards, Pavel --=20 http://www.livejournal.com/~pavelmachek --FFoLq8A0u+X9iRU8 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iEYEARECAAYFAmAce+8ACgkQMOfwapXb+vKLGQCgwvG6KKuDEJFTd5qxHq5/pzQu cM0AmgPB1EkGxKVWU5vD4ONwiUfrYwWM =HeDB -----END PGP SIGNATURE----- --FFoLq8A0u+X9iRU8--