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=-15.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,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 EE40EC4707F for ; Fri, 28 May 2021 00:02:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C5831613BA for ; Fri, 28 May 2021 00:02:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235933AbhE1AEI (ORCPT ); Thu, 27 May 2021 20:04:08 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36664 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235696AbhE1AEF (ORCPT ); Thu, 27 May 2021 20:04:05 -0400 Received: from mail-pj1-x1030.google.com (mail-pj1-x1030.google.com [IPv6:2607:f8b0:4864:20::1030]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AC675C061574; Thu, 27 May 2021 17:02:29 -0700 (PDT) Received: by mail-pj1-x1030.google.com with SMTP id f8so1539776pjh.0; Thu, 27 May 2021 17:02:29 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id; bh=NrZavczs0MF8tqdeaU/rr2uBfm1FCnanDV4vtlGL8eQ=; b=BGP08nCqsa2o3kZ9ZJeK95PtCPZwmjIlwuRj/1GAbtQ9m4JMjbAFHpv1b+nw1LZYfg 7lDBGS9RdNenHYktTGzz+cJsGKrcReYpj+dGcXgmXoDfq/WVXt/A1jlAFC0rZO1nZf8a zfio6Q18LToGNbzBAc1tt8gpmTgQAmkHLJV9l5L+lMHDKejr1HvqZmcEnyz/QAbt8ovc 5EP4cWIUUa1xPnsM4Q+sejEdr0ec1Ar6YtQoY9kalwzdt1QuDJXafnv8U+yWFAzyG/P1 +mu0wTMYxxr9erWga4Efd/AxH3MPUnSGIxtrwKhOoMfiiJaszekCKoBxIrrh+q3DesM0 cPQA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id; bh=NrZavczs0MF8tqdeaU/rr2uBfm1FCnanDV4vtlGL8eQ=; b=ZOCT935RchZNzEVfGcbbrDfA5ETogpQQug7ifQp5egdeFGRDJISlZ+u1wnJu1/2WxM vk9rNLbtFNWn6w+p6/Nv/rdkWPmzaaCqzYmxJxzXqEOlxME7uzb2ssCHBhmhJRT9z6yr jwNzneiHajuih1eX1J2iXpmyorLoFYuJRc5XNW/PgZnE3AC7UH6TcxPyMq39IzsGXNOa 78OTfagVBhWPVMGE4pZ1qDUd2KReZSWfRHcVnr70BzIzFyYq6UPz4nbzfXKhIAvdAwfe UjwuDNbScRPs4D5EWP0TAi7bb0Tb/+2RJKhbDkswxfJFfFpSZ/+1VwnSJnDifAM63ebA BX6A== X-Gm-Message-State: AOAM530FlZGU++IT0YGo6xar10HWKjIdDVwXbhqRJxDYhouxFeLbYsJ9 pjWz0em4B95NlOO0PPzBG0A5SUdCjCw= X-Google-Smtp-Source: ABdhPJylwVntfhyEImkOcMhIXJJySVS5uZe3jihEgU3SrdOXEH8ipfurtx5JzV+a8xDLMsGEUd/PSQ== X-Received: by 2002:a17:902:265:b029:fa:9420:d2fd with SMTP id 92-20020a1709020265b02900fa9420d2fdmr5462176plc.39.1622160148947; Thu, 27 May 2021 17:02:28 -0700 (PDT) Received: from localhost.localdomain ([203.205.141.56]) by smtp.googlemail.com with ESMTPSA id l126sm2726245pga.41.2021.05.27.17.02.26 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Thu, 27 May 2021 17:02:28 -0700 (PDT) From: Wanpeng Li X-Google-Original-From: Wanpeng Li To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: Paolo Bonzini , Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel Subject: [PATCH v4 1/2] KVM: X86: Fix warning caused by stale emulation context Date: Thu, 27 May 2021 17:01:36 -0700 Message-Id: <1622160097-37633-1-git-send-email-wanpengli@tencent.com> X-Mailer: git-send-email 2.7.4 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Wanpeng Li Reported by syzkaller: WARNING: CPU: 7 PID: 10526 at linux/arch/x86/kvm//x86.c:7621 x86_emulate_instruction+0x41b/0x510 [kvm] RIP: 0010:x86_emulate_instruction+0x41b/0x510 [kvm] Call Trace: kvm_mmu_page_fault+0x126/0x8f0 [kvm] vmx_handle_exit+0x11e/0x680 [kvm_intel] vcpu_enter_guest+0xd95/0x1b40 [kvm] kvm_arch_vcpu_ioctl_run+0x377/0x6a0 [kvm] kvm_vcpu_ioctl+0x389/0x630 [kvm] __x64_sys_ioctl+0x8e/0xd0 do_syscall_64+0x3c/0xb0 entry_SYSCALL_64_after_hwframe+0x44/0xae Commit 4a1e10d5b5d8 ("KVM: x86: handle hardware breakpoints during emulation()) adds hardware breakpoints check before emulation the instruction and parts of emulation context initialization, actually we don't have the EMULTYPE_NO_DECODE flag here and the emulation context will not be reused. Commit c8848cee74ff ("KVM: x86: set ctxt->have_exception in x86_decode_insn()) triggers the warning because it catches the stale emulation context has #UD, however, it is not during instruction decoding which should result in EMULATION_FAILED. This patch fixes it by moving the second part emulation context initialization into init_emulate_ctxt() and before hardware breakpoints check. The ctxt->ud will be dropped by a follow-up patch. syzkaller source: https://syzkaller.appspot.com/x/repro.c?x=134683fdd00000 Reported-by: syzbot+71271244f206d17f6441@syzkaller.appspotmail.com Fixes: 4a1e10d5b5d8 (KVM: x86: handle hardware breakpoints during emulation) Signed-off-by: Wanpeng Li --- v3 -> v4: * warning relative path * not move ctxt->ud v2 -> v3: * squash ctxt->ud v1 -> v2: * move the second part emulation context initialization into init_emulate_ctxt() arch/x86/kvm/x86.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index bbc4e04..dba8077 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -7226,6 +7226,11 @@ static void init_emulate_ctxt(struct kvm_vcpu *vcpu) BUILD_BUG_ON(HF_SMM_MASK != X86EMUL_SMM_MASK); BUILD_BUG_ON(HF_SMM_INSIDE_NMI_MASK != X86EMUL_SMM_INSIDE_NMI_MASK); + ctxt->interruptibility = 0; + ctxt->have_exception = false; + ctxt->exception.vector = -1; + ctxt->perm_ok = false; + init_decode_cache(ctxt); vcpu->arch.emulate_regs_need_sync_from_vcpu = false; } @@ -7561,11 +7566,6 @@ int x86_decode_emulated_instruction(struct kvm_vcpu *vcpu, int emulation_type, kvm_vcpu_check_breakpoint(vcpu, &r)) return r; - ctxt->interruptibility = 0; - ctxt->have_exception = false; - ctxt->exception.vector = -1; - ctxt->perm_ok = false; - ctxt->ud = emulation_type & EMULTYPE_TRAP_UD; r = x86_decode_insn(ctxt, insn, insn_len); -- 2.7.4