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=-7.1 required=3.0 tests=BAYES_00,DKIM_ADSP_CUSTOM_MED, DKIM_INVALID,DKIM_SIGNED,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,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 92A23C433DF for ; Mon, 24 Aug 2020 16:43:05 +0000 (UTC) Received: from mm01.cs.columbia.edu (mm01.cs.columbia.edu [128.59.11.253]) by mail.kernel.org (Postfix) with ESMTP id 0B1E52067C for ; Mon, 24 Aug 2020 16:43:04 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="ZOiYUyUZ" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0B1E52067C Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvmarm-bounces@lists.cs.columbia.edu Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 674C34BBCD; Mon, 24 Aug 2020 12:43:04 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu Authentication-Results: mm01.cs.columbia.edu (amavisd-new); dkim=softfail (fail, message has been altered) header.i=@gmail.com Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id Mivuj5anxhEk; Mon, 24 Aug 2020 12:43:03 -0400 (EDT) Received: from mm01.cs.columbia.edu (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 4DA5C4CBF2; Mon, 24 Aug 2020 12:43:03 -0400 (EDT) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 0F4EE4CBEF for ; Mon, 24 Aug 2020 12:43:02 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id rScTBmkGT+Xn for ; Mon, 24 Aug 2020 12:43:01 -0400 (EDT) Received: from mail-pj1-f65.google.com (mail-pj1-f65.google.com [209.85.216.65]) by mm01.cs.columbia.edu (Postfix) with ESMTPS id E2C6D4BBCD for ; Mon, 24 Aug 2020 12:43:00 -0400 (EDT) Received: by mail-pj1-f65.google.com with SMTP id nv17so4606199pjb.3 for ; Mon, 24 Aug 2020 09:43:00 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=w41OmkoPspYNv6XjOAw8ahtDnY6c9BDmvOxAxpZTttk=; b=ZOiYUyUZBx+y2twZVDLNRNj7XcDKPZeSrlH1pKR2XVXQPyltnrUiF5XIL2Pi3UOJE0 QESR928QCAsMbVv7IvrTsNl9dzQkt7ttEVo22hbkdd8dUrifgdVOREvnTvtePmoSa168 LUMoDzFfey129AAzeHQzzhMcEFJEBuPwK0iIGyg5eV7eeKQsyzjJYoSHqPx+kktCO0WP gucacHnk+svFErQYZFyKb3ISKViLF8l6FlE982tB0lCYr6KbI36mn3lZKElTno2t7VnW 88Qp4uOlQ1ROHrTxVoECzjBJHSxrk7CtSabgsYgfuVEBBLi35E8V9OKPG1xS/gAt6i3x vcgg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=w41OmkoPspYNv6XjOAw8ahtDnY6c9BDmvOxAxpZTttk=; b=XeU8DXh2weMH77Hqbzb1qk/lFJKDCs94K8QEU37RIkzbCmzn9dhnZQAEoqfUXLcR/6 n5szODA1b7+f9HcQriIDqE0lIiX+ZiYwQFMpl+2kfNJG1/CS78gXsGkfBprtYNborAXO hnwjHpe2T2WcRMJTTFEXTqMFnCi8vibroTEczFWJELjS67X40jEXwpAMQxbTSQ7by2Od d/FBBkJMYVYvJrsSmUS5YpQ2vLcJaVL/CATUq3iIqtd3zCE+ZyHSPlvXyD7vc3HXmodD zLtJiLBPyOA6zwZmKzsqTveGs56Xlvh5opw+/hr1MfkPI7ufhrkYPgRKNAxkct1SqkJY yegA== X-Gm-Message-State: AOAM532QMYZbEDjqLhhciTIDjUVeUgRItaWspGcxEjJtk6gP+Ire0+mh 0ykApve4b81uCZaMmzcH1rP6zF/Wplc= X-Google-Smtp-Source: ABdhPJxoYGplA4PD2xcotuP1hn0qFIYRCnXteeEmPRirh/XXpaV6W9tmtVZLocyIxdzG6AVoTaXu5g== X-Received: by 2002:a17:90a:850b:: with SMTP id l11mr142577pjn.15.1598287375409; Mon, 24 Aug 2020 09:42:55 -0700 (PDT) Received: from [10.67.51.206] ([192.19.223.252]) by smtp.gmail.com with ESMTPSA id 2sm72768pjg.32.2020.08.24.09.42.53 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 24 Aug 2020 09:42:54 -0700 (PDT) Subject: Re: [PATCH stable v4.9 v2] arm64: entry: Place an SB sequence following an ERET instruction To: Will Deacon References: <20200709195034.15185-1-f.fainelli@gmail.com> <20200720130411.GB494210@kroah.com> <9c29080e-8b3a-571c-3296-e0487fa473fa@gmail.com> <20200807131429.GB664450@kroah.com> <20200821160316.GE21517@willie-the-truck> <7480435b-355d-b9f7-3a42-b72a9c4b6f63@gmail.com> <20200824163208.GA25316@willie-the-truck> From: Florian Fainelli Message-ID: Date: Mon, 24 Aug 2020 09:42:53 -0700 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Firefox/78.0 Thunderbird/78.1.1 MIME-Version: 1.0 In-Reply-To: <20200824163208.GA25316@willie-the-truck> Content-Language: en-US Cc: Nick Desaulniers , Catalin Marinas , Fangrui Song , Marc Zyngier , Will Deacon , open list , stable@vger.kernel.org, "open list:KERNEL VIRTUAL MACHINE FOR ARM64 \(KVM/arm64\)" , Mark Brown , Sami Tolvanen , Greg KH , Kristina Martsenko , Ard Biesheuvel , linux-arm-kernel@lists.infradead.org X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu On 8/24/2020 9:32 AM, Will Deacon wrote: > Hi Florian, > > On Fri, Aug 21, 2020 at 10:16:23AM -0700, Florian Fainelli wrote: >> On 8/21/20 9:03 AM, Will Deacon wrote: >>> On Fri, Aug 07, 2020 at 03:14:29PM +0200, Greg KH wrote: >>>> On Thu, Aug 06, 2020 at 01:00:54PM -0700, Florian Fainelli wrote: >>>>> Greg, did you have a chance to queue those changes for 4.9, 4.14 and 4.19? >>>>> >>>>> https://lore.kernel.org/linux-arm-kernel/20200720182538.13304-1-f.fainelli@gmail.com/ >>>>> https://lore.kernel.org/linux-arm-kernel/20200720182937.14099-1-f.fainelli@gmail.com/ >>>>> https://lore.kernel.org/linux-arm-kernel/20200709195034.15185-1-f.fainelli@gmail.com/ >>>> >>>> Nope, I was waiting for Will's "ack" for these. >>> >>> This patch doesn't even build for me (the 'sb' macro is not defined in 4.9), >>> and I really wonder why we bother backporting it at all. Nobody's ever shown >>> it to be a problem in practice, and it's clear that this is just being >>> submitted to tick a box rather than anything else (otherwise it would build, >>> right?). >> >> Doh, I completely missed submitting the patch this depended on that's >> why I did not notice the build failure locally, sorry about that, what a >> shame. >> >> Would not be the same "tick a box" argument be used against your >> original submission then? Sure, I have not been able to demonstrate in >> real life this was a problem, however the same can be said about a lot >> security related fixes. > > Sort of, although I wrote the original patch because it was dead easy to do > and saved having to think too much about the problem, whereas the complexity > of backporting largerly diminishes that imo. > >> What if it becomes exploitable in the future, would not it be nice to >> have it in a 6 year LTS kernel? > > Even if people are stuck on an old LTS, they should still be taking the > regular updates for it, and we would obviously need to backport the fix if > it turned out to be exploitable (and hey, we could even test it then!). > >>> So I'm not going to Ack any of them. As with a lot of this side-channel >>> stuff the cure is far worse than the disease. >> Assuming that my v3 does build correctly, which it will, would you be >> keen on changing your position? > > Note that I'm not trying to block this patch from going in, I'm just saying > that I'm not supportive of it. Perhaps somebody from Arm can review it if > they think it's worth the effort. How about I submit the actual full series (two patches) and we take the discussion from there? Thanks for responding! -- Florian _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm