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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 2580CC43460 for ; Sat, 10 Apr 2021 15:33:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F0893611AE for ; Sat, 10 Apr 2021 15:33:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234852AbhDJPeB (ORCPT ); Sat, 10 Apr 2021 11:34:01 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42232 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234536AbhDJPeA (ORCPT ); Sat, 10 Apr 2021 11:34:00 -0400 Received: from mail.skyhub.de (mail.skyhub.de [IPv6:2a01:4f8:190:11c2::b:1457]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4CCE9C06138A for ; Sat, 10 Apr 2021 08:33:45 -0700 (PDT) Received: from zn.tnic (p200300ec2f1aea005aa758d9575cf1c9.dip0.t-ipconnect.de [IPv6:2003:ec:2f1a:ea00:5aa7:58d9:575c:f1c9]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.skyhub.de (SuperMail on ZX Spectrum 128k) with ESMTPSA id E30F11EC0409; Sat, 10 Apr 2021 17:33:42 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1618068823; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:in-reply-to:in-reply-to: references:references; bh=JU+alkv88K3AjjKG+MMMv2hhK+iQ284WVJBIZRCDjo0=; b=sNmzpVJFSF7X2weFcgRoe8TQVNxZj3AcD84Z1x3QZS9H4OfyVqGYB7sXKOg5RRB87p0PFn Ep3sPN2Rt40xq9MTbiDFK8EHOsliB6UsXhzv0ik1WcqZIIEwvvnHrZ9DDtWRm8QcX4Nn6c j03I92wuKT+JQN5bt66LIZ1lPRnH7WY= Date: Sat, 10 Apr 2021 17:33:38 +0200 From: Borislav Petkov To: Andy Lutomirski Cc: Thomas Gleixner , Feng Tang , Ingo Molnar , "H . Peter Anvin" , Peter Zijlstra , x86@kernel.org, linux-kernel@vger.kernel.org, rui.zhang@intel.com, andi.kleen@intel.com, dave.hansen@intel.com, len.brown@intel.com Subject: [PATCH -v1.1] x86/msr: Block writes to certain MSRs unconditionally Message-ID: <20210410153338.GD21691@zn.tnic> References: <20210410121144.GC21691@zn.tnic> <437BACC3-A1F7-4C65-80C7-98F6652A14E6@amacapital.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <437BACC3-A1F7-4C65-80C7-98F6652A14E6@amacapital.net> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Apr 10, 2021 at 07:51:58AM -0700, Andy Lutomirski wrote: > Can you add STAR, CSTAR, LSTAR, SYSENTER*, SYSCALL*, and EFER please? Sure. --- From: Borislav Petkov Date: Sat, 10 Apr 2021 14:08:13 +0200 There are a bunch of MSRs which luserspace has no business poking at, whatsoever. Add a ban list and put the TSC-related MSRs and the ring0-entry and features control MSRs in there. Issue a big juicy splat to catch offenders. Signed-off-by: Borislav Petkov --- arch/x86/kernel/msr.c | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+) diff --git a/arch/x86/kernel/msr.c b/arch/x86/kernel/msr.c index ed8ac6bcbafb..2435a619cd9f 100644 --- a/arch/x86/kernel/msr.c +++ b/arch/x86/kernel/msr.c @@ -78,6 +78,21 @@ static ssize_t msr_read(struct file *file, char __user *buf, return bytes ? bytes : err; } +static const u32 msr_ban_list[] = { + MSR_IA32_TSC, + MSR_TSC_AUX, + MSR_IA32_TSC_ADJUST, + MSR_IA32_TSC_DEADLINE, + MSR_EFER, + MSR_STAR, + MSR_CSTAR, + MSR_LSTAR, + MSR_SYSCALL_MASK, + MSR_IA32_SYSENTER_CS, + MSR_IA32_SYSENTER_ESP, + MSR_IA32_SYSENTER_EIP, +}; + static int filter_write(u32 reg) { /* @@ -89,6 +104,16 @@ static int filter_write(u32 reg) * avoid saturating the ring buffer. */ static DEFINE_RATELIMIT_STATE(fw_rs, 30 * HZ, 1); + int i; + + for (i = 0; i < ARRAY_SIZE(msr_ban_list); i++) { + if (msr_ban_list[i] != reg) + continue; + + WARN_ONCE(1, "Blocked write to MSR 0x%x.\n", reg); + + return -EINVAL; + } switch (allow_writes) { case MSR_WRITES_ON: return 0; -- 2.29.2 -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette