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=-9.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED, 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 8C6C1C2F3A6 for ; Mon, 21 Jan 2019 12:48:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 67C3E2085A for ; Mon, 21 Jan 2019 12:48:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728723AbfAUMsx (ORCPT ); Mon, 21 Jan 2019 07:48:53 -0500 Received: from mail-lf1-f67.google.com ([209.85.167.67]:41274 "EHLO mail-lf1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728163AbfAUMsx (ORCPT ); Mon, 21 Jan 2019 07:48:53 -0500 Received: by mail-lf1-f67.google.com with SMTP id c16so15392154lfj.8; Mon, 21 Jan 2019 04:48:52 -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=1rik5yWAwK/VZEgE3GAP/26Xz0u6FKuRPpB5cNtjyms=; b=DPX5QiPhJznBlN+vd9vjGMrvlZHwpxjKSnx/xYYTu78H+7dtbwb6SDDFt9k8ctKTZJ jCDw1zkqT4M1gRWR+yFi+DjLwcI0sVFEkqf/UM3qd1XoCTkVcxApEH5fOh9HMSoX/4kl 7dp2281IwD0fTEr6I+UU42CsHYVQ5qJr6CZXZB4K7u3nz6k/Fyu0TcL6oe5DjtCnCnI7 s1vXtqpu6Id2g45nnsoRT4CFXERR+ZfSBXZsj4GITk3KMGTTbKYUkM1aumfQ0qfylIQd w/0lJg11ZMhLkugoi5nXESvChIRZRZsVQkoufy6v7IEL8QzF7CcVeBT7ceMEAE5e4Iwi vZHQ== X-Gm-Message-State: AJcUukcEHeptivX6crbwUNmZ/VBBHEmBt8aMFrlHwVzK9HvW/nmXoelB ulj5V2TUk5e1bOYpOVVIkRc= X-Google-Smtp-Source: ALg8bN6Ko9Iwu5fWvCaS60yLSJRKSDsyvVKlRT85yCEdok16q+tqefY4oIBm6IlKhLSI8+XxIIXszw== X-Received: by 2002:a19:c70a:: with SMTP id x10mr17898358lff.88.1548074931300; Mon, 21 Jan 2019 04:48:51 -0800 (PST) Received: from localhost.localdomain ([213.87.132.221]) by smtp.gmail.com with ESMTPSA id k68-v6sm2288537ljb.35.2019.01.21.04.48.49 (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Mon, 21 Jan 2019 04:48:50 -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 v2] KVM: x86: Fix single-step debugging Date: Mon, 21 Jan 2019 15:48:40 +0300 Message-Id: <1548074920-10651-1-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 on Jun 7, 2017 the commit c8401dda2f0a00cd25c0 ("KVM: x86: fix singlestepping over syscall") 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. Signed-off-by: Alexander Popov --- 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