netdev - Re: WARNING in hso_free_net

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Date:   Thu, 5 Sep 2019 22:05:54 -0400
From:   Hui Peng <benquike@...il.com>
To:     Andrey Konovalov <andreyknvl@...gle.com>
Cc:     Stephen Hemminger <stephen@...workplumber.org>,
        syzbot+44d53c7255bb1aea22d2@...kaller.appspotmail.com,
        alexios.zavras@...el.com, "David S. Miller" <davem@...emloft.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        USB list <linux-usb@...r.kernel.org>,
        Mathias Payer <mathias.payer@...elwelt.net>,
        netdev <netdev@...r.kernel.org>, rfontana@...hat.com,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Oliver Neukum <oneukum@...e.com>
Subject: Re: WARNING in hso_free_net_device



On 9/5/2019 7:24 AM, Andrey Konovalov wrote:
> On Thu, Sep 5, 2019 at 4:20 AM Hui Peng <benquike@...il.com> wrote:
>>
>> Can you guys have  a look at the attached patch?
> 
> Let's try it:
> 
> #syz test: https://github.com/google/kasan.git eea39f24
> 
> FYI: there are two more reports coming from this driver, which might
> (or might not) have the same root cause. One of them has a suggested
> fix by Oliver.
> 
> https://syzkaller.appspot.com/bug?extid=67b2bd0e34f952d0321e
> https://syzkaller.appspot.com/bug?extid=93f2f45b19519b289613
> 

I think they are different, though similar.
This one is resulted from unregistering a network device.
These 2 are resulted from unregistering a tty device.

>>
>> On 9/4/19 6:41 PM, Stephen Hemminger wrote:
>>> On Wed, 4 Sep 2019 16:27:50 -0400
>>> Hui Peng <benquike@...il.com> wrote:
>>>
>>>> Hi, all:
>>>>
>>>> I looked at the bug a little.
>>>>
>>>> The issue is that in the error handling code, hso_free_net_device
>>>> unregisters
>>>>
>>>> the net_device (hso_net->net)  by calling unregister_netdev. In the
>>>> error handling code path,
>>>>
>>>> hso_net->net has not been registered yet.
>>>>
>>>> I think there are two ways to solve the issue:
>>>>
>>>> 1. fix it in drivers/net/usb/hso.c to avoiding unregistering the
>>>> net_device when it is still not registered
>>>>
>>>> 2. fix it in unregister_netdev. We can add a field in net_device to
>>>> record whether it is registered, and make unregister_netdev return if
>>>> the net_device is not registered yet.
>>>>
>>>> What do you guys think ?
>>> #1