linux-kernel - Re: BUG: selftest/net/tun: Hang in unregister

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Date:   Tue, 14 Mar 2023 21:10:55 +0100
From:   Mirsad Goran Todorovac <mirsad.todorovac@....unizg.hr>
To:     Eric Dumazet <edumazet@...gle.com>
Cc:     netdev@...r.kernel.org, linux-kselftest@...r.kernel.org,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, Shuah Khan <shuah@...nel.org>,
        linux-kernel@...r.kernel.org
Subject: Re: BUG: selftest/net/tun: Hang in unregister_netdevice

On 14. 03. 2023. 17:02, Eric Dumazet wrote:
> On Tue, Mar 14, 2023 at 9:01 AM Mirsad Todorovac
> <mirsad.todorovac@....unizg.hr> wrote:
> 
>> After a while, kernel message start looping:
>>
>>   kernel:unregister_netdevice: waiting for tap0 to become free. Usage count = 3
>>
>> Message from syslogd@...mtodorov at Mar 14 16:57:15 ...
>>   kernel:unregister_netdevice: waiting for tap0 to become free. Usage count = 3
>>
>> Message from syslogd@...mtodorov at Mar 14 16:57:24 ...
>>   kernel:unregister_netdevice: waiting for tap0 to become free. Usage count = 3
>>
>> Message from syslogd@...mtodorov at Mar 14 16:57:26 ...
>>   kernel:unregister_netdevice: waiting for tap0 to become free. Usage count = 3
>>
>> This hangs processes until very late stage of shutdown.
>>
>> I can confirm that CONFIG_DEBUG_{KOBJECT,KOBJECT_RELEASE}=y were the only changes
>> to .config in between builds.
>>
>> Best regards,
>> Mirsad
>>
> 
> Try adding in your config
> 
> CONFIG_NET_DEV_REFCNT_TRACKER=y
> CONFIG_NET_NS_REFCNT_TRACKER=y
> 
> Thanks.

Not at all.

According to the info here: https://cateee.net/lkddb/web-lkddb/NET_DEV_REFCNT_TRACKER.html
no kerenel param was needed.

I have got the same hang, and additional debug information appears to be this
(in /var/log/messages):

Mar 14 20:58:20 pc-mtodorov kernel: unregister_netdevice: waiting for tap0 to become free. Usage count = 3
Mar 14 20:58:20 pc-mtodorov kernel: leaked reference.
Mar 14 20:58:20 pc-mtodorov kernel: net_rx_queue_update_kobjects+0x75/0x1d0
Mar 14 20:58:20 pc-mtodorov kernel: netif_set_real_num_rx_queues+0x5b/0xb0
Mar 14 20:58:20 pc-mtodorov kernel: tun_attach+0x1ec/0x5a0
Mar 14 20:58:20 pc-mtodorov kernel: __tun_chr_ioctl+0xa58/0x17d0
Mar 14 20:58:20 pc-mtodorov kernel: tun_chr_ioctl+0x17/0x20
Mar 14 20:58:20 pc-mtodorov kernel: __x64_sys_ioctl+0x97/0xd0
Mar 14 20:58:20 pc-mtodorov kernel: do_syscall_64+0x5c/0x90
Mar 14 20:58:20 pc-mtodorov kernel: entry_SYSCALL_64_after_hwframe+0x72/0xdc
Mar 14 20:58:20 pc-mtodorov kernel: leaked reference.
Mar 14 20:58:20 pc-mtodorov kernel: netdev_queue_update_kobjects+0x86/0x190
Mar 14 20:58:20 pc-mtodorov kernel: netif_set_real_num_tx_queues+0x86/0x250
Mar 14 20:58:20 pc-mtodorov kernel: tun_attach+0x1d7/0x5a0
Mar 14 20:58:20 pc-mtodorov kernel: __tun_chr_ioctl+0xa58/0x17d0
Mar 14 20:58:20 pc-mtodorov kernel: tun_chr_ioctl+0x17/0x20
Mar 14 20:58:20 pc-mtodorov kernel: __x64_sys_ioctl+0x97/0xd0
Mar 14 20:58:20 pc-mtodorov kernel: do_syscall_64+0x5c/0x90
Mar 14 20:58:20 pc-mtodorov kernel: entry_SYSCALL_64_after_hwframe+0x72/0xdc
Mar 14 20:58:20 pc-mtodorov kernel: unregister_netdevice: waiting for tap0 to become free. Usage count = 3
Mar 14 20:58:20 pc-mtodorov kernel: leaked reference.
Mar 14 20:58:20 pc-mtodorov kernel: net_rx_queue_update_kobjects+0x75/0x1d0
Mar 14 20:58:20 pc-mtodorov kernel: netif_set_real_num_rx_queues+0x5b/0xb0
Mar 14 20:58:20 pc-mtodorov kernel: tun_attach+0x1ec/0x5a0
Mar 14 20:58:20 pc-mtodorov kernel: __tun_chr_ioctl+0xa58/0x17d0
Mar 14 20:58:20 pc-mtodorov kernel: tun_chr_ioctl+0x17/0x20
Mar 14 20:58:20 pc-mtodorov kernel: __x64_sys_ioctl+0x97/0xd0
Mar 14 20:58:20 pc-mtodorov kernel: do_syscall_64+0x5c/0x90
Mar 14 20:58:20 pc-mtodorov kernel: entry_SYSCALL_64_after_hwframe+0x72/0xdc
Mar 14 20:58:20 pc-mtodorov kernel: leaked reference.
Mar 14 20:58:20 pc-mtodorov kernel: netdev_queue_update_kobjects+0x86/0x190
Mar 14 20:58:20 pc-mtodorov kernel: netif_set_real_num_tx_queues+0x86/0x250
Mar 14 20:58:20 pc-mtodorov kernel: tun_attach+0x1d7/0x5a0
Mar 14 20:58:20 pc-mtodorov kernel: __tun_chr_ioctl+0xa58/0x17d0
Mar 14 20:58:20 pc-mtodorov kernel: tun_chr_ioctl+0x17/0x20
Mar 14 20:58:20 pc-mtodorov kernel: __x64_sys_ioctl+0x97/0xd0
Mar 14 20:58:20 pc-mtodorov kernel: do_syscall_64+0x5c/0x90
Mar 14 20:58:20 pc-mtodorov kernel: entry_SYSCALL_64_after_hwframe+0x72/0xdc
Mar 14 20:58:30 pc-mtodorov kernel: unregister_netdevice: waiting for tap0 to become free. Usage count = 3
Mar 14 20:58:30 pc-mtodorov kernel: leaked reference.
Mar 14 20:58:30 pc-mtodorov kernel: net_rx_queue_update_kobjects+0x75/0x1d0
Mar 14 20:58:30 pc-mtodorov kernel: netif_set_real_num_rx_queues+0x5b/0xb0
Mar 14 20:58:30 pc-mtodorov kernel: tun_attach+0x1ec/0x5a0
Mar 14 20:58:30 pc-mtodorov kernel: __tun_chr_ioctl+0xa58/0x17d0
Mar 14 20:58:30 pc-mtodorov kernel: tun_chr_ioctl+0x17/0x20
Mar 14 20:58:30 pc-mtodorov kernel: __x64_sys_ioctl+0x97/0xd0
Mar 14 20:58:30 pc-mtodorov kernel: do_syscall_64+0x5c/0x90
Mar 14 20:58:30 pc-mtodorov kernel: entry_SYSCALL_64_after_hwframe+0x72/0xdc
Mar 14 20:58:30 pc-mtodorov kernel: leaked reference.
Mar 14 20:58:30 pc-mtodorov kernel: netdev_queue_update_kobjects+0x86/0x190
Mar 14 20:58:30 pc-mtodorov kernel: netif_set_real_num_tx_queues+0x86/0x250
Mar 14 20:58:30 pc-mtodorov kernel: tun_attach+0x1d7/0x5a0
Mar 14 20:58:30 pc-mtodorov kernel: __tun_chr_ioctl+0xa58/0x17d0
Mar 14 20:58:30 pc-mtodorov kernel: tun_chr_ioctl+0x17/0x20
Mar 14 20:58:30 pc-mtodorov kernel: __x64_sys_ioctl+0x97/0xd0
Mar 14 20:58:30 pc-mtodorov kernel: do_syscall_64+0x5c/0x90
Mar 14 20:58:30 pc-mtodorov kernel: entry_SYSCALL_64_after_hwframe+0x72/0xdc
Mar 14 20:58:30 pc-mtodorov kernel: unregister_netdevice: waiting for tap0 to become free. Usage count = 3
Mar 14 20:58:30 pc-mtodorov kernel: leaked reference.
Mar 14 20:58:30 pc-mtodorov kernel: net_rx_queue_update_kobjects+0x75/0x1d0
Mar 14 20:58:30 pc-mtodorov kernel: netif_set_real_num_rx_queues+0x5b/0xb0
Mar 14 20:58:30 pc-mtodorov kernel: tun_attach+0x1ec/0x5a0
Mar 14 20:58:30 pc-mtodorov kernel: __tun_chr_ioctl+0xa58/0x17d0
Mar 14 20:58:30 pc-mtodorov kernel: tun_chr_ioctl+0x17/0x20
Mar 14 20:58:30 pc-mtodorov kernel: __x64_sys_ioctl+0x97/0xd0
Mar 14 20:58:30 pc-mtodorov kernel: do_syscall_64+0x5c/0x90
Mar 14 20:58:30 pc-mtodorov kernel: entry_SYSCALL_64_after_hwframe+0x72/0xdc
Mar 14 20:58:30 pc-mtodorov kernel: leaked reference.
Mar 14 20:58:30 pc-mtodorov kernel: netdev_queue_update_kobjects+0x86/0x190
Mar 14 20:58:30 pc-mtodorov kernel: netif_set_real_num_tx_queues+0x86/0x250
Mar 14 20:58:30 pc-mtodorov kernel: tun_attach+0x1d7/0x5a0
Mar 14 20:58:30 pc-mtodorov kernel: __tun_chr_ioctl+0xa58/0x17d0
Mar 14 20:58:30 pc-mtodorov kernel: tun_chr_ioctl+0x17/0x20
Mar 14 20:58:30 pc-mtodorov kernel: __x64_sys_ioctl+0x97/0xd0
Mar 14 20:58:30 pc-mtodorov kernel: do_syscall_64+0x5c/0x90
Mar 14 20:58:30 pc-mtodorov kernel: entry_SYSCALL_64_after_hwframe+0x72/0xdc
Mar 14 20:58:40 pc-mtodorov kernel: unregister_netdevice: waiting for tap0 to become free. Usage count = 3
Mar 14 20:58:40 pc-mtodorov kernel: leaked reference.
Mar 14 20:58:40 pc-mtodorov kernel: net_rx_queue_update_kobjects+0x75/0x1d0
Mar 14 20:58:40 pc-mtodorov kernel: netif_set_real_num_rx_queues+0x5b/0xb0
Mar 14 20:58:40 pc-mtodorov kernel: tun_attach+0x1ec/0x5a0
Mar 14 20:58:40 pc-mtodorov kernel: __tun_chr_ioctl+0xa58/0x17d0
Mar 14 20:58:40 pc-mtodorov kernel: tun_chr_ioctl+0x17/0x20
Mar 14 20:58:40 pc-mtodorov kernel: __x64_sys_ioctl+0x97/0xd0
Mar 14 20:58:40 pc-mtodorov kernel: do_syscall_64+0x5c/0x90
Mar 14 20:58:40 pc-mtodorov kernel: entry_SYSCALL_64_after_hwframe+0x72/0xdc
Mar 14 20:58:40 pc-mtodorov kernel: leaked reference.
Mar 14 20:58:40 pc-mtodorov kernel: netdev_queue_update_kobjects+0x86/0x190
Mar 14 20:58:40 pc-mtodorov kernel: netif_set_real_num_tx_queues+0x86/0x250
Mar 14 20:58:40 pc-mtodorov kernel: tun_attach+0x1d7/0x5a0
Mar 14 20:58:40 pc-mtodorov kernel: __tun_chr_ioctl+0xa58/0x17d0
Mar 14 20:58:40 pc-mtodorov kernel: tun_chr_ioctl+0x17/0x20
Mar 14 20:58:40 pc-mtodorov kernel: __x64_sys_ioctl+0x97/0xd0
Mar 14 20:58:40 pc-mtodorov kernel: do_syscall_64+0x5c/0x90
Mar 14 20:58:40 pc-mtodorov kernel: entry_SYSCALL_64_after_hwframe+0x72/0xdc
Mar 14 20:58:40 pc-mtodorov kernel: unregister_netdevice: waiting for tap0 to become free. Usage count = 3
Mar 14 20:58:40 pc-mtodorov kernel: leaked reference.
Mar 14 20:58:40 pc-mtodorov kernel: net_rx_queue_update_kobjects+0x75/0x1d0
Mar 14 20:58:40 pc-mtodorov kernel: netif_set_real_num_rx_queues+0x5b/0xb0
Mar 14 20:58:40 pc-mtodorov kernel: tun_attach+0x1ec/0x5a0
Mar 14 20:58:40 pc-mtodorov kernel: __tun_chr_ioctl+0xa58/0x17d0
Mar 14 20:58:40 pc-mtodorov kernel: tun_chr_ioctl+0x17/0x20
Mar 14 20:58:40 pc-mtodorov kernel: __x64_sys_ioctl+0x97/0xd0
Mar 14 20:58:40 pc-mtodorov kernel: do_syscall_64+0x5c/0x90
Mar 14 20:58:40 pc-mtodorov kernel: entry_SYSCALL_64_after_hwframe+0x72/0xdc
Mar 14 20:58:40 pc-mtodorov kernel: leaked reference.
Mar 14 20:58:40 pc-mtodorov kernel: netdev_queue_update_kobjects+0x86/0x190
Mar 14 20:58:40 pc-mtodorov kernel: netif_set_real_num_tx_queues+0x86/0x250
Mar 14 20:58:40 pc-mtodorov kernel: tun_attach+0x1d7/0x5a0
Mar 14 20:58:40 pc-mtodorov kernel: __tun_chr_ioctl+0xa58/0x17d0
Mar 14 20:58:40 pc-mtodorov kernel: tun_chr_ioctl+0x17/0x20
Mar 14 20:58:40 pc-mtodorov kernel: __x64_sys_ioctl+0x97/0xd0
Mar 14 20:58:40 pc-mtodorov kernel: do_syscall_64+0x5c/0x90
Mar 14 20:58:40 pc-mtodorov kernel: entry_SYSCALL_64_after_hwframe+0x72/0xdc
Mar 14 20:58:50 pc-mtodorov kernel: unregister_netdevice: waiting for tap0 to become free. Usage count = 3
Mar 14 20:58:50 pc-mtodorov kernel: leaked reference.
Mar 14 20:58:50 pc-mtodorov kernel: net_rx_queue_update_kobjects+0x75/0x1d0
Mar 14 20:58:50 pc-mtodorov kernel: netif_set_real_num_rx_queues+0x5b/0xb0
Mar 14 20:58:50 pc-mtodorov kernel: tun_attach+0x1ec/0x5a0
Mar 14 20:58:50 pc-mtodorov kernel: __tun_chr_ioctl+0xa58/0x17d0
Mar 14 20:58:50 pc-mtodorov kernel: tun_chr_ioctl+0x17/0x20
Mar 14 20:58:50 pc-mtodorov kernel: __x64_sys_ioctl+0x97/0xd0
Mar 14 20:58:50 pc-mtodorov kernel: do_syscall_64+0x5c/0x90
Mar 14 20:58:50 pc-mtodorov kernel: entry_SYSCALL_64_after_hwframe+0x72/0xdc
Mar 14 20:58:50 pc-mtodorov kernel: leaked reference.
Mar 14 20:58:50 pc-mtodorov kernel: netdev_queue_update_kobjects+0x86/0x190
Mar 14 20:58:50 pc-mtodorov kernel: netif_set_real_num_tx_queues+0x86/0x250
Mar 14 20:58:50 pc-mtodorov kernel: tun_attach+0x1d7/0x5a0
Mar 14 20:58:50 pc-mtodorov kernel: __tun_chr_ioctl+0xa58/0x17d0
Mar 14 20:58:50 pc-mtodorov kernel: tun_chr_ioctl+0x17/0x20
Mar 14 20:58:50 pc-mtodorov kernel: __x64_sys_ioctl+0x97/0xd0
Mar 14 20:58:50 pc-mtodorov kernel: do_syscall_64+0x5c/0x90
Mar 14 20:58:50 pc-mtodorov kernel: entry_SYSCALL_64_after_hwframe+0x72/0xdc
Mar 14 20:58:50 pc-mtodorov kernel: unregister_netdevice: waiting for tap0 to become free. Usage count = 3
Mar 14 20:58:50 pc-mtodorov kernel: leaked reference.
Mar 14 20:58:50 pc-mtodorov kernel: net_rx_queue_update_kobjects+0x75/0x1d0
Mar 14 20:58:50 pc-mtodorov kernel: netif_set_real_num_rx_queues+0x5b/0xb0
Mar 14 20:58:50 pc-mtodorov kernel: tun_attach+0x1ec/0x5a0
Mar 14 20:58:50 pc-mtodorov kernel: __tun_chr_ioctl+0xa58/0x17d0
Mar 14 20:58:50 pc-mtodorov kernel: tun_chr_ioctl+0x17/0x20
Mar 14 20:58:50 pc-mtodorov kernel: __x64_sys_ioctl+0x97/0xd0
Mar 14 20:58:50 pc-mtodorov kernel: do_syscall_64+0x5c/0x90
Mar 14 20:58:50 pc-mtodorov kernel: entry_SYSCALL_64_after_hwframe+0x72/0xdc
Mar 14 20:58:50 pc-mtodorov kernel: leaked reference.
Mar 14 20:58:50 pc-mtodorov kernel: netdev_queue_update_kobjects+0x86/0x190
Mar 14 20:58:50 pc-mtodorov kernel: netif_set_real_num_tx_queues+0x86/0x250
Mar 14 20:58:50 pc-mtodorov kernel: tun_attach+0x1d7/0x5a0
Mar 14 20:58:50 pc-mtodorov kernel: __tun_chr_ioctl+0xa58/0x17d0
Mar 14 20:58:50 pc-mtodorov kernel: tun_chr_ioctl+0x17/0x20
Mar 14 20:58:50 pc-mtodorov kernel: __x64_sys_ioctl+0x97/0xd0
Mar 14 20:58:50 pc-mtodorov kernel: do_syscall_64+0x5c/0x90
Mar 14 20:58:50 pc-mtodorov kernel: entry_SYSCALL_64_after_hwframe+0x72/0xdc
Mar 14 20:58:57 pc-mtodorov kernel: kmemleak: 1 new suspected memory leaks (see /sys/kernel/debug/kmemleak)
Mar 14 20:59:00 pc-mtodorov kernel: unregister_netdevice: waiting for tap0 to become free. Usage count = 3
Mar 14 20:59:00 pc-mtodorov kernel: leaked reference.
Mar 14 20:59:00 pc-mtodorov kernel: net_rx_queue_update_kobjects+0x75/0x1d0
Mar 14 20:59:00 pc-mtodorov kernel: netif_set_real_num_rx_queues+0x5b/0xb0
Mar 14 20:59:00 pc-mtodorov kernel: tun_attach+0x1ec/0x5a0
Mar 14 20:59:00 pc-mtodorov kernel: __tun_chr_ioctl+0xa58/0x17d0
Mar 14 20:59:00 pc-mtodorov kernel: tun_chr_ioctl+0x17/0x20
Mar 14 20:59:00 pc-mtodorov kernel: __x64_sys_ioctl+0x97/0xd0
Mar 14 20:59:00 pc-mtodorov kernel: do_syscall_64+0x5c/0x90
Mar 14 20:59:00 pc-mtodorov kernel: entry_SYSCALL_64_after_hwframe+0x72/0xdc
Mar 14 20:59:00 pc-mtodorov kernel: leaked reference.
Mar 14 20:59:00 pc-mtodorov kernel: netdev_queue_update_kobjects+0x86/0x190
Mar 14 20:59:00 pc-mtodorov kernel: netif_set_real_num_tx_queues+0x86/0x250
Mar 14 20:59:00 pc-mtodorov kernel: tun_attach+0x1d7/0x5a0
Mar 14 20:59:00 pc-mtodorov kernel: __tun_chr_ioctl+0xa58/0x17d0
Mar 14 20:59:00 pc-mtodorov kernel: tun_chr_ioctl+0x17/0x20
Mar 14 20:59:00 pc-mtodorov kernel: __x64_sys_ioctl+0x97/0xd0
Mar 14 20:59:00 pc-mtodorov kernel: do_syscall_64+0x5c/0x90
Mar 14 20:59:00 pc-mtodorov kernel: entry_SYSCALL_64_after_hwframe+0x72/0xdc
Mar 14 20:59:01 pc-mtodorov kernel: unregister_netdevice: waiting for tap0 to become free. Usage count = 3
Mar 14 20:59:01 pc-mtodorov kernel: leaked reference.
Mar 14 20:59:01 pc-mtodorov kernel: net_rx_queue_update_kobjects+0x75/0x1d0
Mar 14 20:59:01 pc-mtodorov kernel: netif_set_real_num_rx_queues+0x5b/0xb0
Mar 14 20:59:01 pc-mtodorov kernel: tun_attach+0x1ec/0x5a0
Mar 14 20:59:01 pc-mtodorov kernel: __tun_chr_ioctl+0xa58/0x17d0
Mar 14 20:59:01 pc-mtodorov kernel: tun_chr_ioctl+0x17/0x20
Mar 14 20:59:01 pc-mtodorov kernel: __x64_sys_ioctl+0x97/0xd0
Mar 14 20:59:01 pc-mtodorov kernel: do_syscall_64+0x5c/0x90
Mar 14 20:59:01 pc-mtodorov kernel: entry_SYSCALL_64_after_hwframe+0x72/0xdc
Mar 14 20:59:01 pc-mtodorov kernel: leaked reference.
Mar 14 20:59:01 pc-mtodorov kernel: netdev_queue_update_kobjects+0x86/0x190
Mar 14 20:59:01 pc-mtodorov kernel: netif_set_real_num_tx_queues+0x86/0x250
Mar 14 20:59:01 pc-mtodorov kernel: tun_attach+0x1d7/0x5a0
Mar 14 20:59:01 pc-mtodorov kernel: __tun_chr_ioctl+0xa58/0x17d0
Mar 14 20:59:01 pc-mtodorov kernel: tun_chr_ioctl+0x17/0x20
Mar 14 20:59:01 pc-mtodorov kernel: __x64_sys_ioctl+0x97/0xd0
Mar 14 20:59:01 pc-mtodorov kernel: do_syscall_64+0x5c/0x90
Mar 14 20:59:01 pc-mtodorov kernel: entry_SYSCALL_64_after_hwframe+0x72/0xdc
Mar 14 20:59:10 pc-mtodorov kernel: unregister_netdevice: waiting for tap0 to become free. Usage count = 3
Mar 14 20:59:10 pc-mtodorov kernel: leaked reference.
Mar 14 20:59:10 pc-mtodorov kernel: net_rx_queue_update_kobjects+0x75/0x1d0
Mar 14 20:59:10 pc-mtodorov kernel: netif_set_real_num_rx_queues+0x5b/0xb0
Mar 14 20:59:10 pc-mtodorov kernel: tun_attach+0x1ec/0x5a0
Mar 14 20:59:10 pc-mtodorov kernel: __tun_chr_ioctl+0xa58/0x17d0
Mar 14 20:59:10 pc-mtodorov kernel: tun_chr_ioctl+0x17/0x20
Mar 14 20:59:10 pc-mtodorov kernel: __x64_sys_ioctl+0x97/0xd0
Mar 14 20:59:10 pc-mtodorov kernel: do_syscall_64+0x5c/0x90
Mar 14 20:59:10 pc-mtodorov kernel: entry_SYSCALL_64_after_hwframe+0x72/0xdc
Mar 14 20:59:10 pc-mtodorov kernel: leaked reference.
Mar 14 20:59:10 pc-mtodorov kernel: netdev_queue_update_kobjects+0x86/0x190
Mar 14 20:59:10 pc-mtodorov kernel: netif_set_real_num_tx_queues+0x86/0x250
Mar 14 20:59:10 pc-mtodorov kernel: tun_attach+0x1d7/0x5a0
Mar 14 20:59:10 pc-mtodorov kernel: __tun_chr_ioctl+0xa58/0x17d0
Mar 14 20:59:10 pc-mtodorov kernel: tun_chr_ioctl+0x17/0x20
Mar 14 20:59:10 pc-mtodorov kernel: __x64_sys_ioctl+0x97/0xd0
Mar 14 20:59:10 pc-mtodorov kernel: do_syscall_64+0x5c/0x90
Mar 14 20:59:10 pc-mtodorov kernel: entry_SYSCALL_64_after_hwframe+0x72/0xdc
Mar 14 20:59:11 pc-mtodorov kernel: unregister_netdevice: waiting for tap0 to become free. Usage count = 3
Mar 14 20:59:11 pc-mtodorov kernel: leaked reference.
Mar 14 20:59:11 pc-mtodorov kernel: net_rx_queue_update_kobjects+0x75/0x1d0
Mar 14 20:59:11 pc-mtodorov kernel: netif_set_real_num_rx_queues+0x5b/0xb0
Mar 14 20:59:11 pc-mtodorov kernel: tun_attach+0x1ec/0x5a0
Mar 14 20:59:11 pc-mtodorov kernel: __tun_chr_ioctl+0xa58/0x17d0
Mar 14 20:59:11 pc-mtodorov kernel: tun_chr_ioctl+0x17/0x20
Mar 14 20:59:11 pc-mtodorov kernel: __x64_sys_ioctl+0x97/0xd0
Mar 14 20:59:11 pc-mtodorov kernel: do_syscall_64+0x5c/0x90
Mar 14 20:59:11 pc-mtodorov kernel: entry_SYSCALL_64_after_hwframe+0x72/0xdc
Mar 14 20:59:11 pc-mtodorov kernel: leaked reference.
Mar 14 20:59:11 pc-mtodorov kernel: netdev_queue_update_kobjects+0x86/0x190
Mar 14 20:59:11 pc-mtodorov kernel: netif_set_real_num_tx_queues+0x86/0x250
Mar 14 20:59:11 pc-mtodorov kernel: tun_attach+0x1d7/0x5a0
Mar 14 20:59:11 pc-mtodorov kernel: __tun_chr_ioctl+0xa58/0x17d0
Mar 14 20:59:11 pc-mtodorov kernel: tun_chr_ioctl+0x17/0x20
Mar 14 20:59:11 pc-mtodorov kernel: __x64_sys_ioctl+0x97/0xd0
Mar 14 20:59:11 pc-mtodorov kernel: do_syscall_64+0x5c/0x90
Mar 14 20:59:11 pc-mtodorov kernel: entry_SYSCALL_64_after_hwframe+0x72/0xdc
[root@...mtodorov marvin]# 

I see those "leaked reference" lines are being printed here:
https://elixir.bootlin.com/linux/v6.3-rc2/source/lib/ref_tracker.c#L55

However, it is beyond the scope of my knowledge to track the actual leak.

Hope this helps.

Best regards,
Mirsad

-- 
Mirsad Goran Todorovac
Sistem inženjer
Grafički fakultet | Akademija likovnih umjetnosti
Sveučilište u Zagrebu
 
System engineer
Faculty of Graphic Arts | Academy of Fine Arts
University of Zagreb, Republic of Croatia
The European Union