netdev - Re: [PATCH] [PATCH net] net: Do not hold the reference for the same sk_rx

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Date:   Thu, 16 Mar 2017 10:12:55 +0000
From:   Kevin Xu <kaiwen.xu@...u.com>
To:     Jakub Sitnicki <jkbs@...hat.com>
CC:     "davem@...emloft.net" <davem@...emloft.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH] [PATCH net] net: Do not hold the reference for the same
 sk_rx_dst.

Do you mean the message looping endlessly?

If so, then I suppose it's a different bug.

Kevin

> On Mar 16, 2017, at 3:01 AM, Jakub Sitnicki <jkbs@...hat.com> 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 <kaiwen.xu@...u.com>
>> ---
> 
> FWIW, with this patch applied I'm still sometimes seeing:
> 
> [  125.928095] unregister_netdevice: waiting for lo to become free. Usage count = 1
> 
> -Jakub