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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 19B85C4332B for ; Thu, 19 Mar 2020 17:39:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EE64320409 for ; Thu, 19 Mar 2020 17:39:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728627AbgCSRj3 (ORCPT ); Thu, 19 Mar 2020 13:39:29 -0400 Received: from mga14.intel.com ([192.55.52.115]:50665 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727738AbgCSRj2 (ORCPT ); Thu, 19 Mar 2020 13:39:28 -0400 IronPort-SDR: lGRe65Fvn0RIp5w8PoNxDLU6MYG7n4/XUEVCNzIPF4qnCF+BRynnuhLGBPYs4IWiUFMnhwt7lc dmVYY+/UV2/Q== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by fmsmga103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 19 Mar 2020 10:39:28 -0700 IronPort-SDR: ZPRFzhgSiT9jQbcRgtc1cApiGfS2EB2VD6ZV4hvWWsCwVorO9ZXxMC8HrCVv1XwlzXPZmgI+0q J1WkJpGjamVA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,572,1574150400"; d="scan'208";a="444657304" Received: from sjchrist-coffee.jf.intel.com (HELO linux.intel.com) ([10.54.74.202]) by fmsmga005.fm.intel.com with ESMTP; 19 Mar 2020 10:39:27 -0700 Date: Thu, 19 Mar 2020 10:39:27 -0700 From: Sean Christopherson To: Paolo Bonzini Cc: syzbot , bp@alien8.de, hpa@zytor.com, jmattson@google.com, joro@8bytes.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, mingo@redhat.com, rkrcmar@redhat.com, syzkaller-bugs@googlegroups.com, tglx@linutronix.de, vkuznets@redhat.com, wanpengli@tencent.com, x86@kernel.org Subject: Re: WARNING in vcpu_enter_guest Message-ID: <20200319173927.GD11305@linux.intel.com> References: <000000000000f965b8059877e5e6@google.com> <00000000000081861f05a132b9cd@google.com> <20200319144952.GB11305@linux.intel.com> <20be9560-fce7-1495-3a83-e2b56dbc2389@redhat.com> <20200319173549.GC11305@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200319173549.GC11305@linux.intel.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 19, 2020 at 10:35:49AM -0700, Sean Christopherson wrote: > On Thu, Mar 19, 2020 at 04:14:55PM +0100, Paolo Bonzini wrote: > > On 19/03/20 15:49, Sean Christopherson wrote: > > > On Thu, Mar 19, 2020 at 03:35:16AM -0700, syzbot wrote: > > >> syzbot has found a reproducer for the following crash on: > > >> > > >> HEAD commit: 5076190d mm: slub: be more careful about the double cmpxch.. > > >> git tree: upstream > > >> console output: https://syzkaller.appspot.com/x/log.txt?x=143ca61de00000 > > >> kernel config: https://syzkaller.appspot.com/x/.config?x=9f894bd92023de02 > > >> dashboard link: https://syzkaller.appspot.com/bug?extid=00be5da1d75f1cc95f6b > > >> compiler: gcc (GCC) 9.0.0 20181231 (experimental) > > >> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10bb4023e00000 > > >> > > >> IMPORTANT: if you fix the bug, please add the following tag to the commit: > > >> Reported-by: syzbot+00be5da1d75f1cc95f6b@syzkaller.appspotmail.com > > > Reproduced with a little tweaking of the reproducer, debug in progress. > > > > > > > I think the WARN_ON at x86.c:2447 is just bogus. You can always get it > > to trigger if garbage is passed to KVM_SET_CLOCK. > > Yep. I worked through logic/math, mostly to gain a wee bit of knowledge > about the clock stuff, and it's sound. The KVM_SET_CLOCK from syzkaller > is simply making time go backwards. Actually, would it make sense to return -EINVAL for KVM_SET_CLOCK if the user tries to make kvmclock_offset go backwards?