linux-kernel - Re: [PATCH net 3/8] idpf: fix possible race in idpf_vport

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Message-ID: <ae493f48-ae07-4091-98dd-db254f2ee12f@intel.com>
Date: Wed, 8 Oct 2025 14:41:40 -0700
From: Jacob Keller <jacob.e.keller@...el.com>
To: "Tantilov, Emil S" <emil.s.tantilov@...el.com>, Jakub Kicinski
	<kuba@...nel.org>
CC: Przemek Kitszel <przemyslaw.kitszel@...el.com>, Andrew Lunn
	<andrew+netdev@...n.ch>, "David S. Miller" <davem@...emloft.net>, "Eric
 Dumazet" <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>, "Pavan Kumar
 Linga" <pavan.kumar.linga@...el.com>, Alexander Lobakin
	<aleksander.lobakin@...el.com>, Willem de Bruijn <willemb@...gle.com>,
	Sridhar Samudrala <sridhar.samudrala@...el.com>, Phani Burra
	<phani.r.burra@...el.com>, Piotr Kwapulinski <piotr.kwapulinski@...el.com>,
	Simon Horman <horms@...nel.org>, Radoslaw Tyl <radoslawx.tyl@...el.com>,
	Jedrzej Jagielski <jedrzej.jagielski@...el.com>, Mateusz Polchlopek
	<mateusz.polchlopek@...el.com>, Anton Nadezhdin <anton.nadezhdin@...el.com>,
	Konstantin Ilichev <konstantin.ilichev@...el.com>, Milena Olech
	<milena.olech@...el.com>, <netdev@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, Joshua Hay <joshua.a.hay@...el.com>,
	Aleksandr Loktionov <aleksandr.loktionov@...el.com>, Chittim Madhu
	<madhu.chittim@...el.com>, Samuel Salin <Samuel.salin@...el.com>
Subject: Re: [PATCH net 3/8] idpf: fix possible race in idpf_vport_stop()



On 10/6/2025 5:07 PM, Tantilov, Emil S wrote:
> 
> 
> On 10/6/2025 10:26 AM, Jakub Kicinski wrote:
>> On Mon, 6 Oct 2025 07:49:32 -0700 Tantilov, Emil S wrote:
>>>> Argh, please stop using the flag based state machines. They CANNOT
>>>> replace locking. If there was proper locking in place it wouldn't
>>>> have mattered when we clear the flag.
>>>
>>> This patch is resolving a bug in the current logic of how the flag is
>>> used (not being atomic and not being cleared properly). I don't think
>>> there is an existing lock in place to address this issue, though we are
>>> looking to refactor the code over time to remove and/or limit how these
>>> flags are used.
>>
>> Can you share more details about the race? If there is no lock in place
>> there's always the risk that:
>>
>>    CPU 0                         CPU 1
>>   idpf_vport_stop()             whatever()
>>                                   if (test_bit(UP))
>>                                    # sees true
>>                                  # !< long IRQ arrives
>>   test_and_clear(UP)
>>     ...
>>     all the rest
>>     ...
>>                                  # > long IRQ ends
>>                                  proceed but UP isn't really set any more
>>
> 
> The specific case I was targeting with this patch is for when both
> idpf_vport_stop() and idpf_addr_unsync(), called via set_rx_mode attempt
> to delete the MAC filters. At least in my testing I have not seen a case
> where the set_rx_mode callback will happen before idpf_vport_stop(). I
> am assuming due to userspace reacting to the removal of the netdevs.
> 
>             rmmod-6089    [021] .....  3521.291596: idpf_remove 
> <-pci_device_remove
>             rmmod-6089    [021] .....  3521.292686: idpf_vport_stop 
> <-idpf_vport_dealloc
>   systemd-resolve-1633    [022] b..1.  3521.295320: idpf_set_rx_mode 
> <-dev_mc_del
>   systemd-resolve-1633    [022] b..1.  3521.295338: idpf_addr_unsync 
> <-__hw_addr_sync_dev
>   systemd-resolve-1633    [022] b..1.  3521.295339: idpf_del_mac_filter 
> <-idpf_addr_unsync
>   systemd-resolve-1633    [022] b..1.  3521.295450: idpf_set_rx_mode 
> <-dev_mc_del
>   systemd-resolve-1633    [022] b..1.  3521.295451: idpf_addr_unsync 
> <-__hw_addr_sync_dev
>   systemd-resolve-1633    [022] b..1.  3521.295451: idpf_del_mac_filter 
> <-idpf_addr_unsync
>             rmmod-6089    [002] .....  3521.934980: idpf_vport_stop 
> <-idpf_vport_dealloc
>   systemd-resolve-1633    [022] b..1.  3522.297299: idpf_set_rx_mode 
> <-dev_mc_del
>   systemd-resolve-1633    [022] b..1.  3522.297316: idpf_addr_unsync 
> <-__hw_addr_sync_dev
>   systemd-resolve-1633    [022] b..1.  3522.297317: idpf_del_mac_filter 
> <-idpf_addr_unsync
>    kworker/u261:2-3157    [037] ...1.  3522.297931: 
> idpf_mac_filter_async_handler: Received invalid MAC filter payload (op 
> 536) (len 0)
>             rmmod-6089    [020] .....  3522.573251: idpf_vport_stop 
> <-idpf_vport_dealloc
>             rmmod-6089    [002] .....  3523.229936: idpf_vport_stop 
> <-idpf_vport_dealloc
>   systemd-resolve-1633    [022] b..1.  3523.311435: idpf_set_rx_mode 
> <-dev_mc_del
>   systemd-resolve-1633    [022] b..1.  3523.311452: idpf_addr_unsync 
> <-__hw_addr_sync_dev
>   systemd-resolve-1633    [022] b..1.  3523.311453: idpf_del_mac_filter 
> <-idpf_addr_unsync
> 
>

Jakub, from this thread it still seems like you won't accept this patch
as-is?

I'm working on a v3 of this series resolving the other issues Simon
pointed out, and want to know if I should continue excluding Emil's
patches for now.

Thanks,
Jake




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