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=-0.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 683F0C433E0 for ; Tue, 26 May 2020 10:16:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 355F52073B for ; Tue, 26 May 2020 10:16:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1590488203; bh=BLF1aeSWrq0oAE8ttqy5E/lpdZVSxkVQ5hkjIbIvKV8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=GdhcokLSyzVQjKWOm91FVXYkfeiTSaaNG3epd6R+BHNXZAXC0OhCRzoVS/Ss9di53 ixzX1Um901CNtLBf4ScLMXpBMyqu+wY9MXTCxpVZuD6CWES55Yt20fFY5pKzybnFTE uPAVg2h1kpAFt26iUom3gdx6G9jrnnDMc4wfyi5g= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728872AbgEZKQm (ORCPT ); Tue, 26 May 2020 06:16:42 -0400 Received: from mail.kernel.org ([198.145.29.99]:47110 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726944AbgEZKQm (ORCPT ); Tue, 26 May 2020 06:16:42 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 8660E2071A; Tue, 26 May 2020 10:16:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1590488202; bh=BLF1aeSWrq0oAE8ttqy5E/lpdZVSxkVQ5hkjIbIvKV8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=VqYSlz8VoIrC2jDUhxsAWfZHyHetd2E3NpQLlcQ0Mxkm3zXgZTrAAvfOfPUH3SN3a 3e2FRNqG5KrIGxaGD+ZntFqYuji1TZtgMJ/78yXHcobrTn++hN4THf7+Ik5pz8S+V+ JPIzAdJ0KK2X0FClI+P57pfziC8inf5dsw+6HSSE= Date: Tue, 26 May 2020 12:16:39 +0200 From: Greg KH To: Peter Zijlstra Cc: Andi Kleen , x86@kernel.org, keescook@chromium.org, linux-kernel@vger.kernel.org, sashal@kernel.org, Andi Kleen , stable@vger.kernel.org Subject: Re: [PATCH v1] x86: Pin cr4 FSGSBASE Message-ID: <20200526101639.GC2759907@kroah.com> References: <20200526052848.605423-1-andi@firstfloor.org> <20200526065618.GC2580410@kroah.com> <20200526075736.GH317569@hirez.programming.kicks-ass.net> <20200526081752.GA2650351@kroah.com> <20200526091745.GC325280@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200526091745.GC325280@hirez.programming.kicks-ass.net> Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Tue, May 26, 2020 at 11:17:45AM +0200, Peter Zijlstra wrote: > On Tue, May 26, 2020 at 10:17:52AM +0200, Greg KH wrote: > > On Tue, May 26, 2020 at 09:57:36AM +0200, Peter Zijlstra wrote: > > > On Tue, May 26, 2020 at 08:56:18AM +0200, Greg KH wrote: > > > > On Mon, May 25, 2020 at 10:28:48PM -0700, Andi Kleen wrote: > > > > > From: Andi Kleen > > > > > > > > > > Since there seem to be kernel modules floating around that set > > > > > FSGSBASE incorrectly, prevent this in the CR4 pinning. Currently > > > > > CR4 pinning just checks that bits are set, this also checks > > > > > that the FSGSBASE bit is not set, and if it is clears it again. > > > > > > > > So we are trying to "protect" ourselves from broken out-of-tree kernel > > > > modules now? Why stop with this type of check, why not just forbid them > > > > entirely if we don't trust them? :) > > > > > > Oh, I have a bunch of patches pending for that :-) > > > > Ah, I thought I had seen something like that go by a while ago. > > > > It's sad that we have to write a "don't do stupid things" checker for > > kernel modules now :( > > Because people... they get stuff from the interweb and run it :/ The > days that admins actually knew what they're doing is long long gone. {sigh} > > > It will basically decode the module text and refuse to load the module > > > for most CPL0 instruction. > > > > Ok, so why would Andi's patch even be needed then? Andi, why post this? > > Andi's patch cures a particularly bad module that floats around that > people use, probably without being aware that it's an insta-root hole. Ok, fair enough, thanks for the context. greg k-h