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=-19.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,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 AF09EC47080 for ; Mon, 31 May 2021 14:44:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 957DA613AE for ; Mon, 31 May 2021 14:44:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232064AbhEaOpw (ORCPT ); Mon, 31 May 2021 10:45:52 -0400 Received: from mail.kernel.org ([198.145.29.99]:39874 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232233AbhEaOnd (ORCPT ); Mon, 31 May 2021 10:43:33 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 1C0466191C; Mon, 31 May 2021 13:54:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1622469260; bh=Y882HNBr82OTL23SUJr6boE7FkGWUjsNDSEkPdh/7vg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=yTLn2v41vHqwg2t/D+ULgl10iQI5NunsV719rda6LEt3QcegpUxQ1+HjIfqXDr+2v U1l+73yCdFH66RDRNxcX1R2lY2ir7odEdFg74RYr3+ZbtMDGLaJVBShBW+t2Zepk4K BzfgDNiyXitbP7vKz1tLpGkHhtQrcnfmoLK3E9aA= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, syzbot+71271244f206d17f6441@syzkaller.appspotmail.com, Wanpeng Li , Sean Christopherson Subject: [PATCH 5.12 129/296] KVM: X86: Fix warning caused by stale emulation context Date: Mon, 31 May 2021 15:13:04 +0200 Message-Id: <20210531130708.232443333@linuxfoundation.org> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210531130703.762129381@linuxfoundation.org> References: <20210531130703.762129381@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Wanpeng Li commit da6393cdd8aaa354b3a2437cd73ebb34cac958e3 upstream. 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 Reviewed-by: Sean Christopherson Message-Id: <1622160097-37633-1-git-send-email-wanpengli@tencent.com> Signed-off-by: Greg Kroah-Hartman --- arch/x86/kvm/x86.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -7115,6 +7115,11 @@ static void init_emulate_ctxt(struct kvm 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; } @@ -7450,11 +7455,6 @@ int x86_decode_emulated_instruction(stru 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);