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=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, 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 349DAC433DF for ; Tue, 26 May 2020 09:22:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 09125207CB for ; Tue, 26 May 2020 09:22:19 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="kgFUWgIl" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388432AbgEZJWS (ORCPT ); Tue, 26 May 2020 05:22:18 -0400 Received: from merlin.infradead.org ([205.233.59.134]:57308 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731622AbgEZJWP (ORCPT ); Tue, 26 May 2020 05:22:15 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.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=fbzELRYcJjrFmOciA2lLMrUinuLmeRjLnUksXmy8vX4=; b=kgFUWgIlVIcg3f3/mKjq51a4XJ hqjU/+PU3gfDPjGGAcNeN4Zc/NJjbP4OIR8DaOk5PgRZW9TMyjilPXvbCcj36bmRwmAWQG+Nj14Qb 78ZtfqFcNCkGRLrXA71CGttYLtaHmHF7Q+BWp7UOCWG+AzIZxCNEVKuoF/XQPWwkWavyNcdSqMkhy Pxqi6rWbPxnlhz9s8TI4Lcxfj9JCqWOXUakuSL3Sg8k63nPf11s+vRbkjLkUM8nwGkUjXrezZ17ye HRNg0iOjOoz9Kk3Si0IC4Jz7gXA5rZkv3VePI5WVYruVQh50VnSiU/8YZxWPev4Ai+msA16tIdxSY t6cLGvLQ==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jdViZ-0004up-CU; Tue, 26 May 2020 09:17:51 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 7522330047A; Tue, 26 May 2020 11:17:45 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 4DBD120BD4F39; Tue, 26 May 2020 11:17:45 +0200 (CEST) Date: Tue, 26 May 2020 11:17:45 +0200 From: Peter Zijlstra To: Greg KH 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: <20200526091745.GC325280@hirez.programming.kicks-ass.net> References: <20200526052848.605423-1-andi@firstfloor.org> <20200526065618.GC2580410@kroah.com> <20200526075736.GH317569@hirez.programming.kicks-ass.net> <20200526081752.GA2650351@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200526081752.GA2650351@kroah.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. > > 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. My patches will be a while (too many things in the fire :/) and will certainly not be for stable.