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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,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 3953BC433E0 for ; Mon, 8 Jun 2020 12:21:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0E6902074B for ; Mon, 8 Jun 2020 12:21:32 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="ALqSfBi4" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729706AbgFHMVb (ORCPT ); Mon, 8 Jun 2020 08:21:31 -0400 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:38806 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1729628AbgFHMV3 (ORCPT ); Mon, 8 Jun 2020 08:21:29 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1591618887; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=gYYB9Ly3dQUty4Eb8fhA0MNTLhKQm7egUF4xyawly9U=; b=ALqSfBi4YfmGDf5GX5h1eQzPAY2fzzq3NjVOjqKuwbNVVOBNeLg7EvukboPE8WgC1Nn2an YEHi0yaFM5zBDm7MIv/a3jWmFyqLmMa5NTkDTwDLgbsUzYgA+sBYo38RGLaz3U202Frpp9 O9z6Tvw/8PZIwCh/PvGnGJvwZXr1vc8= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-133-FBsco_4rN5Oi0ULOYSkAvQ-1; Mon, 08 Jun 2020 08:21:23 -0400 X-MC-Unique: FBsco_4rN5Oi0ULOYSkAvQ-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 67401107ACCD; Mon, 8 Jun 2020 12:21:21 +0000 (UTC) Received: from prarit.bos.redhat.com (prarit-guest.7a2m.lab.eng.bos.redhat.com [10.16.222.26]) by smtp.corp.redhat.com (Postfix) with ESMTP id 8716E1002397; Mon, 8 Jun 2020 12:21:19 +0000 (UTC) From: Prarit Bhargava To: linux-kernel@vger.kernel.org Cc: Prarit Bhargava , Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, "H. Peter Anvin" , Tony Luck , "Peter Zijlstra (Intel)" , Sean Christopherson , Rahul Tanwar , Xiaoyao Li , Ricardo Neri , Dave Hansen Subject: [PATCH v2] x86/split_lock: Sanitize userspace and guest error output Date: Mon, 8 Jun 2020 08:21:14 -0400 Message-Id: <20200608122114.13043-1-prarit@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org There are two problems with kernel messages in fatal mode that were found during testing of guests and userspace programs. The first is that no kernel message is output when the split lock detector is triggered with a userspace program. As a result the userspace process dies from receiving SIGBUS with no indication to the user of what caused the process to die. The second problem is that only the first triggering guest causes a kernel message to be output because the message is output with pr_warn_once(). This also results in a loss of information to the user. While fixing these I noticed that the same message was being output three times so I'm cleaning that up too. Fix fatal mode output, and use consistent messages for fatal and warn modes for both userspace and guests. Signed-off-by: Prarit Bhargava Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Borislav Petkov Cc: x86@kernel.org Cc: "H. Peter Anvin" Cc: Tony Luck Cc: "Peter Zijlstra (Intel)" Cc: Sean Christopherson Cc: Rahul Tanwar Cc: Xiaoyao Li Cc: Ricardo Neri Cc: Dave Hansen --- v2: Do not output a message if CPL 3 Alignment Check is turned on (xiaoyao.li) arch/x86/kernel/cpu/intel.c | 27 +++++++++++++-------------- 1 file changed, 13 insertions(+), 14 deletions(-) diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c index 166d7c355896..e02ec81fe1eb 100644 --- a/arch/x86/kernel/cpu/intel.c +++ b/arch/x86/kernel/cpu/intel.c @@ -1074,10 +1074,17 @@ static void split_lock_init(void) split_lock_verify_msr(sld_state != sld_off); } -static void split_lock_warn(unsigned long ip) +static bool split_lock_warn(unsigned long ip, int fatal_no_warn) { - pr_warn_ratelimited("#AC: %s/%d took a split_lock trap at address: 0x%lx\n", - current->comm, current->pid, ip); + if (fatal_no_warn) + return false; + + pr_warn_ratelimited("#AC: %s/%d %ssplit_lock trap at address: 0x%lx\n", + current->comm, current->pid, + sld_state == sld_fatal ? "fatal " : "", ip); + + if (sld_state == sld_fatal) + return false; /* * Disable the split lock detection for this task so it can make @@ -1086,18 +1093,13 @@ static void split_lock_warn(unsigned long ip) */ sld_update_msr(false); set_tsk_thread_flag(current, TIF_SLD); + return true; } bool handle_guest_split_lock(unsigned long ip) { - if (sld_state == sld_warn) { - split_lock_warn(ip); + if (split_lock_warn(ip, 0)) return true; - } - - pr_warn_once("#AC: %s/%d %s split_lock trap at address: 0x%lx\n", - current->comm, current->pid, - sld_state == sld_fatal ? "fatal" : "bogus", ip); current->thread.error_code = 0; current->thread.trap_nr = X86_TRAP_AC; @@ -1108,10 +1110,7 @@ EXPORT_SYMBOL_GPL(handle_guest_split_lock); bool handle_user_split_lock(struct pt_regs *regs, long error_code) { - if ((regs->flags & X86_EFLAGS_AC) || sld_state == sld_fatal) - return false; - split_lock_warn(regs->ip); - return true; + return split_lock_warn(regs->ip, regs->flags & X86_EFLAGS_AC); } /* -- 2.21.3