Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: WARNING in hso_free_net_device
To:     Andrey Konovalov <andreyknvl@google.com>
Cc:     Stephen Hemminger <stephen@networkplumber.org>,
        syzbot+44d53c7255bb1aea22d2@syzkaller.appspotmail.com,
        alexios.zavras@intel.com, "David S. Miller" <davem@davemloft.net>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        LKML <linux-kernel@vger.kernel.org>,
        USB list <linux-usb@vger.kernel.org>,
        Mathias Payer <mathias.payer@nebelwelt.net>,
        netdev <netdev@vger.kernel.org>, rfontana@redhat.com,
        syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Oliver Neukum <oneukum@suse.com>
References: <0000000000002a95df0591a4f114@google.com>
 <d6e4d2da-66c6-a8fe-2fea-a3435fa7cb54@gmail.com>
 <20190904154140.45dfb398@hermes.lan>
 <285edb24-01f9-3f9d-4946-b2f41ccd0774@gmail.com>
 <CAAeHK+y3eQ7bXvo1tiAkwLCsFkbSU5B+6hsKbdEzkSXP2_Jyzg@mail.gmail.com>
From:   Hui Peng <benquike@gmail.com>
Message-ID: <02ef64cc-5053-e6da-fc59-9970f48064c5@gmail.com>
Date:   Thu, 5 Sep 2019 22:05:54 -0400
User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101
 Thunderbird/68.0
MIME-Version: 1.0
In-Reply-To: <CAAeHK+y3eQ7bXvo1tiAkwLCsFkbSU5B+6hsKbdEzkSXP2_Jyzg@mail.gmail.com>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk


On 9/5/2019 7:24 AM, Andrey Konovalov wrote:
> On Thu, Sep 5, 2019 at 4:20 AM Hui Peng <benquike@gmail.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@gmail.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