Subject: Re: [PATCH] [PATCH net] net: Do not hold the reference for the same sk_rx_dst.

From: Jakub Sitnicki <[email-masked]>
Date: Thu, 16 Mar 2017 11:45:03 +0100

On Thu, Mar 16, 2017 at 10:12 AM GMT, Kevin Xu wrote:
> Do you mean the message looping endlessly?

No, the message is emitted just once. Around 100 seconds after
destroying a few namespaces. Occurs not so often, maybe once per ten
runs.

-Jakub

> If so, then I suppose it's a different bug.
>
> Kevin
>
>> On Mar 16, 2017, at 3:01 AM, Jakub Sitnicki <[email-masked]> wrote:
>>
>>> On Thu, Mar 16, 2017 at 08:08 AM GMT, Kevin Xu wrote:
>>> In some rare cases, inet_sk_rx_dst_set() may be called multiple times
>>> on the same dst, causing reference count leakage. Eventually, it
>>> prevents net_device to be destroyed. The bug then manifested as
>>>
>>> unregister_netdevice: waiting for lo to become free. Usage count = 1
>>>
>>> in the kernel log, preventing new network namespace creation.
>>>
>>> The patch works around the issue by checking whether the socket already
>>> has the same dst set.
>>>
>>> Signed-off-by: Kevin Xu <[email-masked]>
>>> ---
>>
>> FWIW, with this patch applied I'm still sometimes seeing:
>>
>> [  125.928095] unregister_netdevice: waiting for lo to become free. Usage count = 1
>>
>> -Jakub