From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1754069AbdLNSgN (ORCPT <rfc822;w@1wt.eu>);
        Thu, 14 Dec 2017 13:36:13 -0500
Received: from mail-it0-f53.google.com ([209.85.214.53]:40541 "EHLO
        mail-it0-f53.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1753743AbdLNSgL (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Thu, 14 Dec 2017 13:36:11 -0500
X-Google-Smtp-Source: ACJfBoupdkblTLolhYLTfVTwDf5HjgJDM4Md6UxwR8GuARELJHAoUakdp0M5WPrIORxMK0faQOdZXQ==
Date: Thu, 14 Dec 2017 10:36:07 -0800
From: Eric Biggers <ebiggers3@gmail.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Dmitry Vyukov <dvyukov@google.com>, Greg KH <greg@kroah.com>,
        Kees Cook <keescook@chromium.org>,
        Alexey Dobriyan <adobriyan@gmail.com>, security@kernel.org,
        Akinobu Mita <akinobu.mita@gmail.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        LKML <linux-kernel@vger.kernel.org>, Ingo Molnar <mingo@kernel.org>,
        syzkaller-bugs@googlegroups.com,
        Vegard Nossum <vegard.nossum@oracle.com>
Subject: Re: general protection fault in show_timer
Message-ID: <20171214183607.GB259981@gmail.com>
References: <CACVxJT-WEm8KbmSCmQ_EWMRVDcoBp0g-DJRg89CJzi5+sekymg@mail.gmail.com>
 <CACT4Y+aTcJq7hu+azvd37XD09F8-PAXz4hNgKqYzXFb_iZndKQ@mail.gmail.com>
 <CACT4Y+ZGPYH5spxW=R5jn7=JCCo-_nfWvQdQLW7iESO+Lpmf9A@mail.gmail.com>
 <CACVxJT9Q+-1xGkVmdz+e6869Few90E+D8fMQWeSpW=MA76_03A@mail.gmail.com>
 <alpine.DEB.2.20.1711301355450.1925@nanos>
 <CAGXu5j+92ZebfVQHKoH0M3OcrqUC++YFj8EYy=kW7iNaa4_aFQ@mail.gmail.com>
 <20171212083343.GG22935@kroah.com>
 <alpine.DEB.2.20.1712141525300.4998@nanos>
 <CACT4Y+Yu1csMLNa0P=RfEtWC+f0VbnX8Q8L63doWqRJU0c5KLA@mail.gmail.com>
 <alpine.DEB.2.20.1712141631470.4998@nanos>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <alpine.DEB.2.20.1712141631470.4998@nanos>
User-Agent: Mutt/1.5.21 (2010-09-15)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Thu, Dec 14, 2017 at 04:34:12PM +0100, Thomas Gleixner wrote:
> On Thu, 14 Dec 2017, Dmitry Vyukov wrote:
> > On Thu, Dec 14, 2017 at 3:26 PM, Thomas Gleixner <tglx@linutronix.de> wrote:
> > > On Tue, 12 Dec 2017, Greg KH wrote:
> > >> Did this ever go anywhere?  I don't see it in Linus's tree yet...
> > >
> > > I learned yesterday that syzboz is understuffed and cannot test patches, so
> > > I need to find a minute to run the reproducer myself and verify that the
> > > patch is correct.
> > 
> > Hi Thomas,
> > 
> > Why do you say so? Have you tried to ask it to test?
> > https://github.com/google/syzkaller/blob/master/docs/syzbot.md#communication-with-syzbot
> > What happened?
> 
> Eric explained that to me yesterday and I did not try yet. 
> 

Your patch definitely fixes the bug (I tested the C reproducers, you just need
to build a kernel with CONFIG_CHECKPOINT_RESTORE=y and CONFIG_POSIX_TIMERS=y,
then run them).  The real question is whether the check being introduced is too
strict -- are there users passing in other values for ->sigev_notify that would
be broken?  That I can't really answer.

Eric