From patchwork Fri Jan 13 17:59:04 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?b?UmFkaW0gS3LEjW3DocWZ?= X-Patchwork-Id: 9516143 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id B1D54601E5 for ; Fri, 13 Jan 2017 17:59:22 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id A7D50286CB for ; Fri, 13 Jan 2017 17:59:22 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 9C3B928763; Fri, 13 Jan 2017 17:59:22 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 5A4E7286CB for ; Fri, 13 Jan 2017 17:59:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751232AbdAMR7I (ORCPT ); Fri, 13 Jan 2017 12:59:08 -0500 Received: from mx1.redhat.com ([209.132.183.28]:58044 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750996AbdAMR7H (ORCPT ); Fri, 13 Jan 2017 12:59:07 -0500 Received: from smtp.corp.redhat.com (int-mx16.intmail.prod.int.phx2.redhat.com [10.5.11.28]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 182233F20F; Fri, 13 Jan 2017 17:59:08 +0000 (UTC) Received: from potion (dhcp-1-251.brq.redhat.com [10.34.1.251]) by smtp.corp.redhat.com (Postfix) with SMTP id C2931B7F85; Fri, 13 Jan 2017 17:59:05 +0000 (UTC) Received: by potion (sSMTP sendmail emulation); Fri, 13 Jan 2017 18:59:04 +0100 Date: Fri, 13 Jan 2017 18:59:04 +0100 From: Radim =?utf-8?B?S3LEjW3DocWZ?= To: Dmitry Vyukov Cc: Paolo Bonzini , KVM list , LKML , Steve Rutherford , syzkaller Subject: [PATCH] KVM: VMX: downgrade warning on unexpected exit code Message-ID: <20170113175904.GA23569@potion> References: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 2.74 on 10.5.11.28 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.30]); Fri, 13 Jan 2017 17:59:08 +0000 (UTC) Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP 2017-01-02 11:23+0100, Dmitry Vyukov: > Hello, > > I've got the following warning while running syzkaller fuzzer: > > WARNING: CPU: 2 PID: 13257 at arch/x86/kvm/vmx.c:8633 > vmx_handle_exit+0x262b/0x38b0 arch/x86/kvm/vmx.c:8633 > vmx: unexpected exit reason 0xb > CPU: 2 PID: 13257 Comm: syz-executor7 Not tainted 4.10.0-rc1+ #118 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 > Call Trace: > __dump_stack lib/dump_stack.c:15 [inline] > dump_stack+0x292/0x3a2 lib/dump_stack.c:51 > panic+0x1cb/0x3a9 kernel/panic.c:179 > __warn+0x1c4/0x1e0 kernel/panic.c:539 > warn_slowpath_fmt+0xc5/0x100 kernel/panic.c:562 > vmx_handle_exit+0x262b/0x38b0 arch/x86/kvm/vmx.c:8633 > vcpu_enter_guest arch/x86/kvm/x86.c:6884 [inline] > vcpu_run arch/x86/kvm/x86.c:6943 [inline] > kvm_arch_vcpu_ioctl_run+0xf3d/0x45f0 arch/x86/kvm/x86.c:7101 > kvm_vcpu_ioctl+0x673/0x1120 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2569 > vfs_ioctl fs/ioctl.c:43 [inline] > do_vfs_ioctl+0x1bf/0x1780 fs/ioctl.c:683 > SYSC_ioctl fs/ioctl.c:698 [inline] > SyS_ioctl+0x8f/0xc0 fs/ioctl.c:689 > entry_SYSCALL_64_fastpath+0x1f/0xc2 > RIP: 0033:0x4438a9 > RSP: 002b:00007f935aa2fb58 EFLAGS: 00000286 ORIG_RAX: 0000000000000010 > RAX: ffffffffffffffda RBX: 0000000000000015 RCX: 00000000004438a9 > RDX: 0000000000000000 RSI: 000000000000ae80 RDI: 0000000000000015 > RBP: 00000000006ddb30 R08: 0000000000000000 R09: 0000000000000000 > R10: 0000000000000000 R11: 0000000000000286 R12: 0000000000700000 > R13: 0000000000000006 R14: 0000000000000015 R15: 0000000020014000 > Dumping ftrace buffer: > (ftrace buffer empty) > Kernel Offset: disabled > > Exit reason 0xb is GETSEC instruction. This does not look harmful as > it is handled as #UD. But I think we should print a single line > message regarding non-emulated instruction as in other cases, just to > not scare cloud admins and to make syzkaller ignore it. > > FTR, a raw reproducer is here: > https://gist.githubusercontent.com/dvyukov/c762f6ea04ebbba49cdee0a6caca31b4/raw/f21deb04cdc70ae74100c12447d71bb0cd2025c7/gistfile1.txt I can't reproduce -- maybe a nested bug, which will take a while to figure out. Still, host dump at that point is useless, so the change makes sense. A guest dump would be useful (e.g. I think that GETSEC should not exit if guest CR4.SMX is disabled), but just giving the error is about as good and we want something short and rate-limited if the message can be trigerred by a guest in production ... ---8<--- We never needed the call trace and we better rate-limit if it can be triggered by a guest. Signed-off-by: Radim Krčmář --- arch/x86/kvm/vmx.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index a236decb81e4..7cd606daa01e 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -8595,7 +8595,8 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu) && kvm_vmx_exit_handlers[exit_reason]) return kvm_vmx_exit_handlers[exit_reason](vcpu); else { - WARN_ONCE(1, "vmx: unexpected exit reason 0x%x\n", exit_reason); + vcpu_unimpl(vcpu, "vmx: unexpected exit reason 0x%x\n", + exit_reason); kvm_queue_exception(vcpu, UD_VECTOR); return 1; }