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=-6.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_GIT 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 86CDFC7113B for ; Mon, 21 Jan 2019 12:21:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 612472084A for ; Mon, 21 Jan 2019 12:21:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728490AbfAUMVC (ORCPT ); Mon, 21 Jan 2019 07:21:02 -0500 Received: from mail-lf1-f68.google.com ([209.85.167.68]:43928 "EHLO mail-lf1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727926AbfAUMVB (ORCPT ); Mon, 21 Jan 2019 07:21:01 -0500 Received: by mail-lf1-f68.google.com with SMTP id u18so15320404lff.10; Mon, 21 Jan 2019 04:21:00 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:subject:date:message-id; bh=MnVtObA1fJy4gD+z1gL9LPKcmKRhWMJ7sii8yrEXzQM=; b=dGOwpX5RMI2P2azKteXJzfXlLDMvLDfEiY1mnYVgqik7vmhNCy4yEitcVf4IR45k+m 5Cred5MV/U2jjPgNi2TdO929b5iqzEEBu/DLzor3qoeCs92AqOkcdfishzjcJAip70tu M4FXkMPaM9Nhp01hlKlv79JCSm32caf0u5dQrYKJ5ENQ5EHVIMbQ/Je9ubP7HO7W1Nz7 IqCXRfPqdup1vyVyOLiC6aIbZTeX+BgTvdjuAjcmYWudAKo++eEiPwKCU4oaqq++b7sV hXV2lagGprHb+D9OLArz0zLl2H6Hw2lHaKv1W6jTuft/ftYxR1JVSio1CcA/olErVpzn rJxw== X-Gm-Message-State: AJcUukflIFUP36VOdhkm02zRCf6iTo2zbT6zgwBMpp/pKXrq+HJfv39V ElN7XJlU4398KEIB9HJ60/Q= X-Google-Smtp-Source: ALg8bN7DaRXNO4htnXb7bQ9aYJzD0ErtwNDHpFyoNT+R5TOQPCqXKF/fIoRjSqDcmVrUMylc+LF6xg== X-Received: by 2002:a19:cd50:: with SMTP id d77mr17894241lfg.125.1548073259875; Mon, 21 Jan 2019 04:20:59 -0800 (PST) Received: from localhost.localdomain ([213.87.132.221]) by smtp.gmail.com with ESMTPSA id 10sm2256354lff.62.2019.01.21.04.20.58 (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Mon, 21 Jan 2019 04:20:59 -0800 (PST) From: Alexander Popov To: Paolo Bonzini , Radim Krcmar , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Nadav Amit , Andy Lutomirski , Stefan Hajnoczi , H Peter Anvin , x86@kernel.org, kvm@vger.kernel.org, kernel-hardening@lists.openwall.com, linux-kernel@vger.kernel.org, Alexander Popov Subject: [PATCH] KVM: x86: Fix single-step debugging Date: Mon, 21 Jan 2019 15:20:24 +0300 Message-Id: <1548073224-5363-1-git-send-email-alex.popov@linux.com> X-Mailer: git-send-email 2.7.4 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The single-step debugging of KVM guests on x86 is broken: if we run gdb 'stepi' command at the breakpoint when the guest interrupts are enabled, RIP always jumps to native_apic_mem_write(). Then other nasty effects follow. Long investigation showed that the commit c8401dda2f0a00cd25c0 (Jun 7 2017) introduced the kvm_run.debug corruption: kvm_vcpu_do_singlestep() can be called without X86_EFLAGS_TF set. Let's fix it. Please consider that for -stable. --- arch/x86/kvm/x86.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index f049ecf..9686068 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -6407,8 +6407,7 @@ int x86_emulate_instruction(struct kvm_vcpu *vcpu, toggle_interruptibility(vcpu, ctxt->interruptibility); vcpu->arch.emulate_regs_need_sync_to_vcpu = false; kvm_rip_write(vcpu, ctxt->eip); - if (r == EMULATE_DONE && - (ctxt->tf || (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP))) + if (r == EMULATE_DONE && ctxt->tf) kvm_vcpu_do_singlestep(vcpu, &r); if (!ctxt->have_exception || exception_type(ctxt->exception.vector) == EXCPT_TRAP) -- 2.7.4