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=-15.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 83B11C433F5 for ; Tue, 21 Sep 2021 12:02:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6840B60E76 for ; Tue, 21 Sep 2021 12:02:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231277AbhIUMEA (ORCPT ); Tue, 21 Sep 2021 08:04:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58822 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231224AbhIUMD7 (ORCPT ); Tue, 21 Sep 2021 08:03:59 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 17E94C061757; Tue, 21 Sep 2021 05:02:31 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=+kP37EKfXgboCEQjp8x5JVX9fltzDY6I8KswV5Vh4Wg=; b=Rg/ce+rxn3d069LIvENwQTh3O/ orcvaGTo6gb3lnmTYFzP2Vm6cwC4X5yCjQ95vHd8yVW02ArlJS7udQ6C5qKkWpjcP1X+dl0+fObug 06KJl1j0TYOjX7v+uaCMhIOdWdOWLp253WBTOMLtRo7gZqrB6iUgquRJLDLX9GEsCKNRtOsW+WgcO fCmkrpuOnXwYa/Yd3dYqGOKpGwt8lGAfB6HMVea1z/eoYDNv45s5K9jlCcp/B4oaGQ3/G5COK++f6 aU1R583gU+NqJLU3EbpFoQf+EEvXKC3+GE0ef/F2P7P227CwUoPLFT2/sJFmgP4oHtcG00G6UdbgM S0jrmcsw==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1mSeSK-003mGX-2Y; Tue, 21 Sep 2021 12:01:17 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 619F2300274; Tue, 21 Sep 2021 14:00:59 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 43E7D2028E984; Tue, 21 Sep 2021 14:00:59 +0200 (CEST) Date: Tue, 21 Sep 2021 14:00:59 +0200 From: Peter Zijlstra To: Ondrej Zary Cc: linux-kernel@vger.kernel.org, linux-tip-commits@vger.kernel.org, Thomas Gleixner , x86@kernel.org Subject: Re: [tip: x86/core] x86/iopl: Fake iopl(3) CLI/STI usage Message-ID: References: <20210918090641.GD5106@worktop.programming.kicks-ass.net> <163220928593.25758.16098239507716851071.tip-bot2@tip-bot2> <202109211309.26518.linux@zary.sk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <202109211309.26518.linux@zary.sk> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Sep 21, 2021 at 01:09:26PM +0200, Ondrej Zary wrote: > On Tuesday 21 September 2021, tip-bot2 for Peter Zijlstra wrote: > > The following commit has been merged into the x86/core branch of tip: > > > > Commit-ID: 32e1ae626f295152d1fc9a3375214133cbe62878 > > Gitweb: https://git.kernel.org/tip/32e1ae626f295152d1fc9a3375214133cbe62878 > > Author: Peter Zijlstra > > AuthorDate: Fri, 17 Sep 2021 11:20:04 +02:00 > > Committer: Peter Zijlstra > > CommitterDate: Sat, 18 Sep 2021 12:18:32 +02:00 > > > > x86/iopl: Fake iopl(3) CLI/STI usage > > > > Since commit c8137ace5638 ("x86/iopl: Restrict iopl() permission > > scope") it's possible to emulate iopl(3) using ioperm(), except for > > the CLI/STI usage. > > > > Userspace CLI/STI usage is very dubious (read broken), since any > > exception taken during that window can lead to rescheduling anyway (or > > worse). The IOPL(2) manpage even states that usage of CLI/STI is highly > > discouraged and might even crash the system. > > > > Of course, that won't stop people and HP has the dubious honour of > > being the first vendor to be found using this in their hp-health > > package. > > > > In order to enable this 'software' to still 'work', have the #GP treat > > the CLI/STI instructions as NOPs when iopl(3). Warn the user that > > their program is doing dubious things. > > > > Fixes: a24ca9976843 ("x86/iopl: Remove legacy IOPL option") > > Reported-by: Ondrej Zary > > Signed-off-by: Peter Zijlstra (Intel) > > Reviewed-by: Thomas Gleixner > > Link: https://lkml.kernel.org/r/20210918090641.GD5106@worktop.programming.kicks-ass.net > > Could this be backported to 5.10 kernel so it can get into the recently released Debian 11? Thomas also asked about a stable tag, so I'll rebase and force-push these commits and add: Cc: stable@kernel.org # v5.5+ to it.