Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S932986AbeAKUnp (ORCPT <rfc822;ralf@linux-mips.org> + 1 other);
        Thu, 11 Jan 2018 15:43:45 -0500
Received: from mail-it0-f52.google.com ([209.85.214.52]:42369 "EHLO
        mail-it0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S932377AbeAKUno (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Thu, 11 Jan 2018 15:43:44 -0500
X-Google-Smtp-Source: ACJfBovhyMiCVS4fb2howvhYgeD4glcrz/pSS56SyPJLVqBn1ig6njDTkmAHmXQ/TX0K724dbjVZHQ==
From: Vince Weaver <vincent.weaver@maine.edu>
X-Google-Original-From: Vince Weaver <vince@maine.edu>
Date: Thu, 11 Jan 2018 15:43:41 -0500 (EST)
X-X-Sender: vince@macbook-air
To: Vince Weaver <vincent.weaver@maine.edu>
cc: Peter Zijlstra <peterz@infradead.org>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Ingo Molnar <mingo@kernel.org>, linux-kernel@vger.kernel.org,
        Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Andy Lutomirski <luto@kernel.org>
Subject: Re: perf: perf_fuzzer quickly locks up on 4.15-rc7
In-Reply-To: <alpine.DEB.2.21.1801111455450.22460@macbook-air>
Message-ID: <alpine.DEB.2.21.1801111542160.23914@macbook-air>
References: <alpine.DEB.2.21.1801090841300.15884@macbook-air> <20180109151253.GK6176@hirez.programming.kicks-ass.net> <alpine.DEB.2.21.1801091022040.16446@macbook-air> <20180109153341.GL6176@hirez.programming.kicks-ass.net> <alpine.DEB.2.21.1801091052010.16446@macbook-air>
 <20180109160551.GK3040@hirez.programming.kicks-ass.net> <20180109170716.bqmexpmywwr4bwuv@treble> <20180111052538.2qhj6oxnc24xumhk@treble> <alpine.DEB.2.21.1801111358580.22460@macbook-air> <20180111192112.d35nkotzklicd27c@treble> <20180111195018.GB3397@worktop>
 <alpine.DEB.2.21.1801111455450.22460@macbook-air>
User-Agent: Alpine 2.21 (DEB 202 2017-01-01)
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
Return-Path: <linux-kernel-owner@vger.kernel.org>

On Thu, 11 Jan 2018, Vince Weaver wrote:

> On Thu, 11 Jan 2018, Peter Zijlstra wrote:
> 
> > On Thu, Jan 11, 2018 at 01:21:12PM -0600, Josh Poimboeuf wrote:
> > > Yuck.  This time it was stack recursion on the entry stack.  In the
> > > previous error, recursion was detected on the IRQ stack.  Otherwise they
> > > look quite similar.
> > > 
> > > Was that also with nopti?
> > 
> > Both with pti enabled, nopti makes things work again.
> 
> I think I have hit those errors even with pti disabled but now I'll have 
> to double check.

I can confirm this, I am able to trigger the stack recursion warning even 
when "pti=off" is set.

Jan 11 15:34:47 core2 kernel: [  320.668900] WARNING: stack recursion on stack type 4
Jan 11 15:34:47 core2 kernel: [  320.668909] WARNING: can't dereference registers at 00000000d5ae0491 for ip swapgs_restore_regs_and_return_to_usermode+0x28/0x7c

Vince