netdev - Re: [PATCH] vhost/vsock: Fix error handling in vhost_vsock

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Date:   Tue, 8 Nov 2022 18:15:17 +0800
From:   Yuan Can <yuancan@...wei.com>
To:     Stefano Garzarella <sgarzare@...hat.com>
CC:     <stefanha@...hat.com>, <mst@...hat.com>, <jasowang@...hat.com>,
        <davem@...emloft.net>, <kvm@...r.kernel.org>,
        <virtualization@...ts.linux-foundation.org>,
        <netdev@...r.kernel.org>
Subject: Re: [PATCH] vhost/vsock: Fix error handling in vhost_vsock_init()


在 2022/11/8 17:33, Stefano Garzarella 写道:
> On Tue, Nov 08, 2022 at 09:13:57AM +0000, Yuan Can wrote:
>> A problem about modprobe vhost_vsock failed is triggered with the
>> following log given:
>>
>> modprobe: ERROR: could not insert 'vhost_vsock': Device or resource busy
>>
>> The reason is that vhost_vsock_init() returns misc_register() directly
>> without checking its return value, if misc_register() failed, it returns
>> without calling vsock_core_unregister() on vhost_transport, resulting 
>> the
>> vhost_vsock can never be installed later.
>> A simple call graph is shown as below:
>>
>> vhost_vsock_init()
>>   vsock_core_register() # register vhost_transport
>>   misc_register()
>>     device_create_with_groups()
>>       device_create_groups_vargs()
>>         dev = kzalloc(...) # OOM happened
>>   # return without unregister vhost_transport
>>
>> Fix by calling vsock_core_unregister() when misc_register() returns 
>> error.
>
> Thanks for this fix!
>
>>
>> Fixes: c0cfa2d8a788 ("vsock: add multi-transports support")
>
> Is this the right tag?
>
> It seems to me that since the introduction of vhost-vsock we have the 
> same problem (to be solved differently, because with the introduction 
> of multi-transport we refactored the initialization functions).
>
> So should we use 433fc58e6bf2 ("VSOCK: Introduce vhost_vsock.ko")?
Thanks for pointing out this problem! I will use the correct tag in the 
v2 patch.

-- 
Best regards,
Yuan Can