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,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 C8226C3A5AA for ; Wed, 4 Sep 2019 18:23:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A13AC20870 for ; Wed, 4 Sep 2019 18:23:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1567621389; bh=HQhjPHYUPk6eNmJ7SpCrvcFik+rs4bvnYNXZP/mbyy8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=Voh21mj2leCxjTmvWPwk5iOT4QSLHzyWtadxw6jXLDeayAxSnR2IRFhbc9wGeXmZF LQyR5unUMmvpOGbzvBrA17rhaeMGUQ/ED3t4HleN9UzaWH4eEvFd2mS3wadyuqIHuQ LaHKK0te9b7LFBCRhQU8IUKUzOtdw+lR490CgtFM= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388545AbfIDSDR (ORCPT ); Wed, 4 Sep 2019 14:03:17 -0400 Received: from mail.kernel.org ([198.145.29.99]:43682 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388534AbfIDSDQ (ORCPT ); Wed, 4 Sep 2019 14:03:16 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 4134F22CEA; Wed, 4 Sep 2019 18:03:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1567620195; bh=HQhjPHYUPk6eNmJ7SpCrvcFik+rs4bvnYNXZP/mbyy8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Gm07aXBjZrFARFrij9eT2Ppt9dLlVNIfDAX/WnKimDoR7q33arswlLBsSBnyKo0Fr 4AdxubfojCfzxwprW7UWBanE23bPCmqhy7Kr/eyV8TNWso9DpRCas3sZLtsdk+CIOY pO8DTnlEV2i3qQl2MSlrirXd8MlI8EWrYEh1P4eg= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Nadav Amit , Andy Lutomirski , Sean Christopherson , =?UTF-8?q?Radim=20Kr=C4=8Dm=C3=A1=C5=99?= Subject: [PATCH 4.14 25/57] KVM: x86: Dont update RIP or do single-step on faulting emulation Date: Wed, 4 Sep 2019 19:53:53 +0200 Message-Id: <20190904175304.370110671@linuxfoundation.org> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20190904175301.777414715@linuxfoundation.org> References: <20190904175301.777414715@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Sean Christopherson commit 75ee23b30dc712d80d2421a9a547e7ab6e379b44 upstream. Don't advance RIP or inject a single-step #DB if emulation signals a fault. This logic applies to all state updates that are conditional on clean retirement of the emulation instruction, e.g. updating RFLAGS was previously handled by commit 38827dbd3fb85 ("KVM: x86: Do not update EFLAGS on faulting emulation"). Not advancing RIP is likely a nop, i.e. ctxt->eip isn't updated with ctxt->_eip until emulation "retires" anyways. Skipping #DB injection fixes a bug reported by Andy Lutomirski where a #UD on SYSCALL due to invalid state with EFLAGS.TF=1 would loop indefinitely due to emulation overwriting the #UD with #DB and thus restarting the bad SYSCALL over and over. Cc: Nadav Amit Cc: stable@vger.kernel.org Reported-by: Andy Lutomirski Fixes: 663f4c61b803 ("KVM: x86: handle singlestep during emulation") Signed-off-by: Sean Christopherson Signed-off-by: Radim Krčmář Signed-off-by: Greg Kroah-Hartman --- arch/x86/kvm/x86.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -5954,12 +5954,13 @@ restart: unsigned long rflags = kvm_x86_ops->get_rflags(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) - kvm_vcpu_do_singlestep(vcpu, &r); if (!ctxt->have_exception || - exception_type(ctxt->exception.vector) == EXCPT_TRAP) + exception_type(ctxt->exception.vector) == EXCPT_TRAP) { + kvm_rip_write(vcpu, ctxt->eip); + if (r == EMULATE_DONE && ctxt->tf) + kvm_vcpu_do_singlestep(vcpu, &r); __kvm_set_rflags(vcpu, ctxt->eflags); + } /* * For STI, interrupts are shadowed; so KVM_REQ_EVENT will