linux-kernel - Re: [syzbot] upstream test error: WARNING in __queue

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Message-ID: <CANp29Y6gP7Q8F0BbjG6FPcsp9kd5OAtk0J4qybnfGuV=g20_uw@mail.gmail.com>
Date:   Fri, 2 Sep 2022 14:28:52 +0200
From:   Aleksandr Nogikh <nogikh@...gle.com>
To:     Luiz Augusto von Dentz <luiz.dentz@...il.com>
Cc:     Lai Jiangshan <jiangshanlai@...il.com>,
        syzbot <syzbot+243b7d89777f90f7613b@...kaller.appspotmail.com>,
        LKML <linux-kernel@...r.kernel.org>,
        "'Aleksandr Nogikh' via syzkaller-bugs" 
        <syzkaller-bugs@...glegroups.com>, Tejun Heo <tj@...nel.org>,
        Marcel Holtmann <marcel@...tmann.org>,
        Johan Hedberg <johan.hedberg@...il.com>,
        "linux-bluetooth@...r.kernel.org" <linux-bluetooth@...r.kernel.org>
Subject: Re: [syzbot] upstream test error: WARNING in __queue_work

Hi,

This one has so far happened only once on syzbot, probably it's either
an extremely rare issue or was already solved.

On Tue, Aug 30, 2022 at 7:37 PM Luiz Augusto von Dentz
<luiz.dentz@...il.com> wrote:
>
> Hi Lai,
>
> On Tue, Aug 30, 2022 at 7:08 AM Lai Jiangshan <jiangshanlai@...il.com> wrote:
> >
> > CC: BLUETOOTH SUBSYSTEM
> >
> > It seems that hci_cmd_timeout() queues a work to a destroyed workqueue.
>
> Are there any traces or a way to reproduce the problem?

You can take a look at the console log provided in the original bug report:

console output: https://syzkaller.appspot.com/x/log.txt?x=120ebce7080000

Re. reproduction -- syzbot records a test error when it failed to do
the following sequence of steps:
1) Boot a VM and establish an SSH connection to it
2) Upload fuzzer binaries
3) Start fuzzer binaries; these binaries will set up the fuzzing
environment (networking devices, etc)
4) Execute a simple mmap program to check if coverage collection works fine

mmap(0x1ffff000, 0x1000, 0x0, 0x32, 0xffffffffffffffff, 0x0)
mmap(0x20000000, 0x1000000, 0x7, 0x32, 0xffffffffffffffff, 0x0)
map(0x21000000, 0x1000, 0x0, 0x32, 0xffffffffffffffff, 0x0)

It's probably easiest to start syzkaller locally on this exact kernel
revision and see if the fuzzing is able to start. It will perform the
same steps and report an error, if the issue persists.
I've just tried to reproduce this particular bug myself on
4c612826bec1 and everything booted absolutely fine. So probably it was
just a flake.

FWIW syzbot can also perform patch testing for the reported bugs and
output console logs, so it should also simplify the debugging of such
bugs. More details are here:
https://github.com/google/syzkaller/blob/master/docs/syzbot.md#testing-patches

Patch testing can be done if there's a repro, I've just sent a PR
(https://github.com/google/syzkaller/pull/3355) to add testing to the
exception list -- we can retest that without a repro.

Best Regards,
Aleksandr
>
> --
> Luiz Augusto von Dentz
>
> --
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