From patchwork Mon Dec 7 20:45:08 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Adalbert_Laz=C4=83r?= X-Patchwork-Id: 11956671 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=-13.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,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 9C20AC1B0D8 for ; Mon, 7 Dec 2020 20:47:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 56566238A0 for ; Mon, 7 Dec 2020 20:47:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727017AbgLGUrj (ORCPT ); Mon, 7 Dec 2020 15:47:39 -0500 Received: from mx01.bbu.dsd.mx.bitdefender.com ([91.199.104.161]:42566 "EHLO mx01.bbu.dsd.mx.bitdefender.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726181AbgLGUrg (ORCPT ); Mon, 7 Dec 2020 15:47:36 -0500 Received: from smtp.bitdefender.com (smtp01.buh.bitdefender.com [10.17.80.75]) by mx01.bbu.dsd.mx.bitdefender.com (Postfix) with ESMTPS id 00C09305D4FF; Mon, 7 Dec 2020 22:46:13 +0200 (EET) Received: from localhost.localdomain (unknown [91.199.104.27]) by smtp.bitdefender.com (Postfix) with ESMTPSA id CEDC63072785; Mon, 7 Dec 2020 22:46:12 +0200 (EET) From: =?utf-8?q?Adalbert_Laz=C4=83r?= To: kvm@vger.kernel.org Cc: virtualization@lists.linux-foundation.org, Paolo Bonzini , =?utf-8?q?Mihai_Don=C8=9Bu?= , =?utf-8?q?Adalbert_L?= =?utf-8?q?az=C4=83r?= Subject: [PATCH v11 07/81] KVM: x86: avoid injecting #PF when emulate the VMCALL instruction Date: Mon, 7 Dec 2020 22:45:08 +0200 Message-Id: <20201207204622.15258-8-alazar@bitdefender.com> In-Reply-To: <20201207204622.15258-1-alazar@bitdefender.com> References: <20201207204622.15258-1-alazar@bitdefender.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org From: Mihai Donțu It can happened to end up emulating the VMCALL instruction as a result of the handling of an EPT write fault. In this situation, the emulator will try to unconditionally patch the correct hypercall opcode bytes using emulator_write_emulated(). However, this last call uses the fault GPA (if available) or walks the guest page tables at RIP, otherwise. The trouble begins when using VM introspection, when we forbid the use of the fault GPA and fallback to the guest pt walk: in Windows (8.1 and newer) the page that we try to write into is marked read-execute and as such emulator_write_emulated() fails and we inject a write #PF, leading to a guest crash. Signed-off-by: Mihai Donțu Signed-off-by: Adalbert Lazăr --- arch/x86/kvm/x86.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 5951458408fb..816801d6c95d 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -8144,11 +8144,15 @@ static int emulator_fix_hypercall(struct x86_emulate_ctxt *ctxt) struct kvm_vcpu *vcpu = emul_to_vcpu(ctxt); char instruction[3]; unsigned long rip = kvm_rip_read(vcpu); + int err; kvm_x86_ops.patch_hypercall(vcpu, instruction); - return emulator_write_emulated(ctxt, rip, instruction, 3, + err = emulator_write_emulated(ctxt, rip, instruction, 3, &ctxt->exception); + if (err == X86EMUL_PROPAGATE_FAULT) + err = X86EMUL_CONTINUE; + return err; } static int dm_request_for_irq_injection(struct kvm_vcpu *vcpu)