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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E0A58C636D7 for ; Wed, 22 Feb 2023 02:14:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229839AbjBVCOR (ORCPT ); Tue, 21 Feb 2023 21:14:17 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47228 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229822AbjBVCOR (ORCPT ); Tue, 21 Feb 2023 21:14:17 -0500 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4D6846E9F for ; Tue, 21 Feb 2023 18:14:15 -0800 (PST) Received: from kwepemm600017.china.huawei.com (unknown [172.30.72.56]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4PM06C5LRFzKq0X; Wed, 22 Feb 2023 10:12:19 +0800 (CST) Received: from [10.174.179.234] (10.174.179.234) by kwepemm600017.china.huawei.com (7.193.23.234) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.17; Wed, 22 Feb 2023 10:14:12 +0800 Message-ID: <2cf50476-fbe0-24df-ed9b-6a2ed6226ca6@huawei.com> Date: Wed, 22 Feb 2023 10:14:11 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.8.0 Subject: Re: Consultation on backport 97e3d26b5e5f("x86/mm: Randomize per-cpu entry area") to stable To: Seth Jenkins CC: Greg KH , , , Dave Hansen , , References: <2b814e48-d304-e48a-e4b4-c39a10d2dbf4@huawei.com> <2c56661c-d2ca-d1b0-da69-89a5e1f3e67f@huawei.com> From: Tong Tiangen In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.179.234] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To kwepemm600017.china.huawei.com (7.193.23.234) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org 在 2023/2/22 4:26, Seth Jenkins 写道: > > So you are letting an opaque US government agency, and random third > > party companies, dictate your company's internal engineering policies > > and resource allocations?  That feels very very odd and ripe for abuse. > I wholeheartedly agree with gregkh that the CVE system is flawed in > numerous ways and generates many false positives, however in this case, > this issue is a real issue with real security impact that received a > real patch upstream. The idea of backporting this to earlier kernels > probably warrants discussion if someone is willing to bite off that > work. But this gets into the fuzzy "backporting exploit mitigations to > stable" conversation. > > > And are you sure this can really happen?  Have you proven this? > Yes this can really, provably, happen: > https://googleprojectzero.blogspot.com/2022/12/exploiting-CVE-2022-42703-bringing-back-the-stack-attack.html > > > > And why is this really an issue, KAS[L]R is a known-weak-defense and > almost > > useless against local attacks. > Granted, Peter Z's fix does help to mitigate the impact from remote > attackers but yes this fix does not resolve the security impact from > local exploits. Thank you seth. Yes, for this specific CVE issue, KASLR is indeed a mitigation measure. > > > On Tue, Feb 21, 2023 at 7:30 AM Tong Tiangen > wrote: > > > > 在 2023/2/21 18:40, Greg KH 写道: > > On Tue, Feb 21, 2023 at 05:19:42PM +0800, Tong Tiangen wrote: > >> > >> > >> 在 2023/2/21 16:40, Greg KH 写道: > >>> On Tue, Feb 21, 2023 at 03:46:27PM +0800, Tong Tiangen wrote: > >>>> > >>>> > >>>> 在 2023/2/21 15:30, Greg KH 写道: > >>>>> On Tue, Feb 21, 2023 at 03:19:05PM +0800, Tong Tiangen wrote: > >>>>>> Hi peter: > >>>>>> > >>>>>> Do you have any plans to backport this patch[1] to the > stable branch of the > >>>>>> lower version, such as 4.19.y ? > >>>>> > >>>>> Why?  That is a new feature for 6.2 why would it be needed to fix > >>>>> anything in really old kernels? > >>>> > >>>> Hi Greg: > >>>> > >>>> This patch fix CVE-2023-0597[1], > >>> > >>> The kernel developers do not care about CVEs as they are almost > always > >>> invalid and do not mean anything, > >> > >> Ok, thanks. > >> > >> > >>> sorry.  It is well known that, companies like Red Hat use them > to make > >>> up for broken internal engineering policies. > >> > >> Yeah, For company's internal engineering policies, the CVE with > certain > >> impact must be repaired. > > > > So you are letting an opaque US government agency, and random third > > party companies, dictate your company's internal engineering policies > > and resource allocations?  That feels very very odd and ripe for > abuse. > > > > Also note that MITRE refuses to allocate CVEs for many real kernel > > issues for unknown reasons, (i.e. they reject all of my requests), so > > you are getting only a small subset of real issues here. > > > > Also, how do you handle revocation of CVEs that are obviously invalid > > and/or don't actually do anything (like this one?) > > > >>> Are you sure this really is a valid problem that must be fixed > in older > >>> kernels? > >>> > >>>> this CVE report a flaw possibility of memory leak. And this is > >>>> important for some products using this stable version. > >>> > >>> What exact memory leak are you referring to? > >> > >> Sorry for Inaccurate description, the memory leak means: a potential > >> security risk of kernel memory information disclosure caused by no > >> randomization of the exception stacks. > > > > And are you sure this can really happen?  Have you proven this? > > > > And why is this really an issue, KASR is a known-week-defense and > almost > > useless against local attacks. > > > > Anyway, please provide working patches if you think this really is an > > issue. > > > > And please revisit your company's policies, they do not seem very > sane :) > > Hi Greg: > > Thanks for these very useful suggestions and we will revisit our > policies :) > > Thanks, > Tong > . > > > > > thanks, > > > > greg k-h > > . >