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[23.128.96.18]) by mx.google.com with ESMTP id k8si12672042iov.91.2021.05.23.21.37.21; Sun, 23 May 2021 21:37:34 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=suelYebO; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229733AbhEXEiP (ORCPT + 99 others); Mon, 24 May 2021 00:38:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40326 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229530AbhEXEiP (ORCPT ); Mon, 24 May 2021 00:38:15 -0400 Received: from mail-pl1-x635.google.com (mail-pl1-x635.google.com [IPv6:2607:f8b0:4864:20::635]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E7184C061574; Sun, 23 May 2021 21:36:47 -0700 (PDT) Received: by mail-pl1-x635.google.com with SMTP id v13so13978728ple.9; Sun, 23 May 2021 21:36:47 -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=CFKj4h8D3vKVsrArxInuoUkH3K47MAPJEo/4ElSezfw=; b=suelYebOlkPxLUkUTCooa0nu2Vbc9auUsC0ZpGyRD7QqJCvRFdyVW/w4mVNVNPt5nh INTH9AivNniMLt/7OeOVaz39skE253KoNrvaNG76w0EYBVCjpkU4b3boQdlKbiyIjjyc 4smb0q25DNDaEEnnkVCIa0YpeqNJdWaDsCAtj7LzS4OcffH5eeCvRddqgld/RcTUCUX0 nBbnO2919hAuvhh+fA295dm8AlTInxsN61FjykuQ04Oi92fGD6gQJMWXYvdZ/tKD+YRn jpf18KTH6azSK+z3L52gIricwlxHYAqFIBTDWUByKkBs82Fqf4UCeg3Ftw4YR/sw2OnU AwYA== 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=CFKj4h8D3vKVsrArxInuoUkH3K47MAPJEo/4ElSezfw=; b=Pk7vPBusOas1OOvrP9+LPx8HL2l+9l25fxDFUGsP615rNdfyZL4Rm5PopwVIiP2VAG zN9tG2eT9zALg1aWSJxjqY1GyJ3RVE/FkVxxWptcxsWNHbyGvxq6B1HQQFycpm6n4lLg mA8JYVdxdqjuMr6voZfXZQKiK9ZRZ+5xOIK7clLdjGT4VOTtqKYYHwY8QaNyfc75kKg5 oPGlGUIuk7ToW/+OrOyTgnFuULgrsWgMM9tG8z0oih6E3TzlaQtV/TV5MwrAxnf+dPoP MHwOr4XhRh76BfmLy5nq82WZnsAiQ4EHElapXlctMKVwkixoftfSzaotCnqZ59YHPcsr eKOw== X-Gm-Message-State: AOAM531XsG9Ivd/Q1ZhE6+IeWsl5LviN/SRn+10iWuHSskrBcQ63fh78 FAZYb1BypcynX2IoA7MS/hGosBTf9FA= X-Received: by 2002:a17:90a:9517:: with SMTP id t23mr22396886pjo.130.1621831007083; Sun, 23 May 2021 21:36:47 -0700 (PDT) Received: from localhost.localdomain ([203.205.141.56]) by smtp.googlemail.com with ESMTPSA id cc2sm8884703pjb.39.2021.05.23.21.36.43 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Sun, 23 May 2021 21:36:46 -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] KVM: X86: Fix warning caused by stale emulation context Date: Sun, 23 May 2021 21:35:54 -0700 Message-Id: <1621830954-31963-1-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 /home/kernel/ssd/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 4a1e10d5b5d8c (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 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 before hardware breakpoints check. 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 --- arch/x86/kvm/x86.c | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index bbc4e04..eca69f9 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -7552,6 +7552,13 @@ int x86_decode_emulated_instruction(struct kvm_vcpu *vcpu, int emulation_type, init_emulate_ctxt(vcpu); + ctxt->interruptibility = 0; + ctxt->have_exception = false; + ctxt->exception.vector = -1; + ctxt->perm_ok = false; + + ctxt->ud = emulation_type & EMULTYPE_TRAP_UD; + /* * We will reenter on the same instruction since we do not set * complete_userspace_io. This does not handle watchpoints yet, @@ -7561,13 +7568,6 @@ 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); trace_kvm_emulate_insn_start(vcpu); -- 2.7.4