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 6B21EC433B4 for ; Sat, 10 Apr 2021 12:11:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2DFEF611AF for ; Sat, 10 Apr 2021 12:11:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234625AbhDJMMD (ORCPT ); Sat, 10 Apr 2021 08:12:03 -0400 Received: from mail.skyhub.de ([5.9.137.197]:33160 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231279AbhDJMMC (ORCPT ); Sat, 10 Apr 2021 08:12:02 -0400 Received: from zn.tnic (p200300ec2f1aea006082a170ade1e1be.dip0.t-ipconnect.de [IPv6:2003:ec:2f1a:ea00:6082:a170:ade1:e1be]) (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 295201EC0503; Sat, 10 Apr 2021 14:11:47 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1618056707; 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=kPPK/QMaoIar+FjxS46ZX+QeZKTmcaML04EwAs17eoA=; b=cOPHBVMHtx8z+KZh+56NNI8efPVD7MKscwZGsmnizKyR3svhxJ2TUQu2sfApm6T2FId4BO vWlw6I3XxKH8zNQfRmJ21ZJuNksOxyGaFVT+Ok/08Zv/lQWmMdNWT0KHl4dYbTkm7CRLAS MbvJJxjw4yVoRfYHlgJS+8Yzc65Gp4k= Date: Sat, 10 Apr 2021 14:11:44 +0200 From: Borislav Petkov To: Thomas Gleixner Cc: 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] x86/msr: Block writes to certain MSRs unconditionally Message-ID: <20210410121144.GC21691@zn.tnic> References: <1617092747-15769-1-git-send-email-feng.tang@intel.com> <87y2dq32xc.ffs@nanos.tec.linutronix.de> <20210410094752.GB21691@zn.tnic> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20210410094752.GB21691@zn.tnic> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 in there. Issue a big juicy splat to catch offenders. Signed-off-by: Borislav Petkov --- arch/x86/kernel/msr.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/arch/x86/kernel/msr.c b/arch/x86/kernel/msr.c index ed8ac6bcbafb..574bd2c6d4f8 100644 --- a/arch/x86/kernel/msr.c +++ b/arch/x86/kernel/msr.c @@ -78,6 +78,13 @@ 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, +}; + static int filter_write(u32 reg) { /* @@ -89,6 +96,16 @@ 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