netdev - Re: WARNING: ODEBUG bug in netdev

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Message-ID: <CACT4Y+Y_TadXGE_CVFa4fKqrbpAD4i5WGem9StgoyP_YAVraXw@mail.gmail.com>
Date:   Mon, 24 Jun 2019 12:54:25 +0200
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     syzbot <syzbot+c4521ac872a4ccc3afec@...kaller.appspotmail.com>,
        Alexander Duyck <alexander.h.duyck@...el.com>,
        amritha.nambiar@...el.com,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        David Miller <davem@...emloft.net>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Ido Schimmel <idosch@...lanox.com>,
        LKML <linux-kernel@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        tyhicks@...onical.com, wanghai26@...wei.com, yuehaibing@...wei.com
Subject: Re: WARNING: ODEBUG bug in netdev_freemem (2)

On Mon, Jun 24, 2019 at 11:34 AM Thomas Gleixner <tglx@...utronix.de> wrote:
>
> On Mon, 24 Jun 2019, syzbot wrote:
>
> > Hello,
> >
> > syzbot found the following crash on:
> >
> > HEAD commit:    fd6b99fa Merge branch 'akpm' (patches from Andrew)
> > git tree:       upstream
> > console output: https://syzkaller.appspot.com/x/log.txt?x=144de256a00000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=fa9f7e1b6a8bb586
> > dashboard link: https://syzkaller.appspot.com/bug?extid=c4521ac872a4ccc3afec
> > compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> >
> > Unfortunately, I don't have any reproducer for this crash yet.
> >
> > IMPORTANT: if you fix the bug, please add the following tag to the commit:
> > Reported-by: syzbot+c4521ac872a4ccc3afec@...kaller.appspotmail.com
> >
> > device hsr_slave_0 left promiscuous mode
> > team0 (unregistering): Port device team_slave_1 removed
> > team0 (unregistering): Port device team_slave_0 removed
> > bond0 (unregistering): Releasing backup interface bond_slave_1
> > bond0 (unregistering): Releasing backup interface bond_slave_0
> > bond0 (unregistering): Released all slaves
> > ------------[ cut here ]------------
> > ODEBUG: free active (active state 0) object type: timer_list hint:
> > delayed_work_timer_fn+0x0/0x90 arch/x86/include/asm/paravirt.h:767
>
> One of the cleaned up devices has left an active timer which belongs to a
> delayed work. That's all I can decode out of that splat. :(

Hi Thomas,

If ODEBUG would memorize full stack traces for object allocation
(using lib/stackdepot.c), it would make this splat actionable, right?
I've fixed https://bugzilla.kernel.org/show_bug.cgi?id=203969 for this.