Re: [PATCH] net: usb: r8152: Check used MAC passthrough address

[Aaron Ma <aaron.ma@canonical.com>]

On 1/5/22 16:32, Henning Schild wrote:
> Am Wed, 5 Jan 2022 16:01:24 +0800
> schrieb Aaron Ma <aaron.ma@canonical.com>:
> 
>> On 1/5/22 15:55, Henning Schild wrote:
>>> Am Wed, 5 Jan 2022 15:38:51 +0800
>>> schrieb Aaron Ma <aaron.ma@canonical.com>:
>>>    
>>>> On 1/5/22 15:32, Henning Schild wrote:
>>>>> Am Wed, 5 Jan 2022 08:23:55 +0100
>>>>> schrieb Henning Schild <henning.schild@siemens.com>:
>>>>>       
>>>>>> Hi Aaron,
>>>>>>
>>>>>> if this or something similar goes in, please add another patch to
>>>>>> remove the left-over defines.
>>>>>>      
>>>>
>>>> Sure, I will do it.
>>>>   
>>>>>> Am Wed,  5 Jan 2022 14:17:47 +0800
>>>>>> schrieb Aaron Ma <aaron.ma@canonical.com>:
>>>>>>      
>>>>>>> When plugin multiple r8152 ethernet dongles to Lenovo Docks
>>>>>>> or USB hub, MAC passthrough address from BIOS should be
>>>>>>> checked if it had been used to avoid using on other dongles.
>>>>>>>
>>>>>>> Currently builtin r8152 on Dock still can't be identified.
>>>>>>> First detected r8152 will use the MAC passthrough address.
>>>>>>>
>>>>>>> Signed-off-by: Aaron Ma <aaron.ma@canonical.com>
>>>>>>> ---
>>>>>>>     drivers/net/usb/r8152.c | 10 ++++++++++
>>>>>>>     1 file changed, 10 insertions(+)
>>>>>>>
>>>>>>> diff --git a/drivers/net/usb/r8152.c b/drivers/net/usb/r8152.c
>>>>>>> index f9877a3e83ac..77f11b3f847b 100644
>>>>>>> --- a/drivers/net/usb/r8152.c
>>>>>>> +++ b/drivers/net/usb/r8152.c
>>>>>>> @@ -1605,6 +1605,7 @@ static int
>>>>>>> vendor_mac_passthru_addr_read(struct r8152 *tp, struct sockaddr
>>>>>>> *sa) char *mac_obj_name; acpi_object_type mac_obj_type;
>>>>>>>     	int mac_strlen;
>>>>>>> +	struct net_device *ndev;
>>>>>>>     
>>>>>>>     	if (tp->lenovo_macpassthru) {
>>>>>>>     		mac_obj_name = "\\MACA";
>>>>>>> @@ -1662,6 +1663,15 @@ static int
>>>>>>> vendor_mac_passthru_addr_read(struct r8152 *tp, struct sockaddr
>>>>>>> *sa) ret = -EINVAL; goto amacout;
>>>>>>>     	}
>>>>>>> +	rcu_read_lock();
>>>>>>> +	for_each_netdev_rcu(&init_net, ndev) {
>>>>>>> +		if (strncmp(buf, ndev->dev_addr, 6) == 0) {
>>>>>>> +			rcu_read_unlock();
>>>>>>> +			goto amacout;
>>>>>>
>>>>>> Since the original PCI netdev will always be there, that would
>>>>>> disable inheritance would it not?
>>>>>> I guess a strncmp(MODULE_NAME, info->driver, strlen(MODULE_NAME))
>>>>>> is needed as well.
>>>>>>      
>>>>
>>>> PCI ethernet could be a builtin one on dock since there will be
>>>> TBT4 dock.
>>>
>>> In my X280 there is a PCI device in the laptop, always there. And
>>> its MAC is the one found in ACPI. Did not try but i think for such
>>> devices there would never be inheritance even if one wanted and
>>> used a Lenovo dock that is supposed to do it.
>>>    
>>
>> There will more TBT4 docks in market, the new ethernet is just the
>> same as PCI device, connected by thunderbolt.
>>
>> For exmaple, connect a TBT4 dock which uses i225 pcie base ethernet,
>> then connect another TBT3 dock which uses r8152.
>> If skip PCI check, then i225 and r8152 will use the same MAC.
> 
> In current 5.15 i have that sort of collision already. All r8152s will
> happily grab the MAC of the I219. In fact i have only ever seen it with
> one r8152 at a time but while the I219 was actively in use.
> While this patch will probably solve that, i bet it would defeat MAC
> pass-thru altogether. Even when turned on in the BIOS.
> Or does that iterator take "up"/"down" state into consideration? But
> even if, the I219 could become "up" any time later.
> 

No, that's different, I219 got MAC from their own space.
MAC passthrough got MAC from ACPI "\MACA".

> These collisions are simply bound to happen and probably very hard to
> avoid once you have set your mind on allowing pass-thru in the first
> place. Not sure whether that even has potential to disturb network
> equipment like switches.
> 

After check MAC address, it will be more safe.

Aaron

> Henning
> 
>> Aaron
>>
>>> Maybe i should try the patch but it seems like it defeats
>>> inheritance completely. Well depending on probe order ...
>>>
>>> regards,
>>> Henning
>>>
>>>    
>>>>>> Maybe leave here with
>>>>>> netif_info()
>>>>>>      
>>>>
>>>> Not good to print in rcu lock.
>>>>   
>>>>>> And move the whole block up, we can skip the whole ACPI story if
>>>>>> we find the MAC busy.
>>>>>
>>>>> That is wrong, need to know that MAC so can not move up too much.
>>>>> But maybe above the is_valid_ether_addr
>>>>
>>>> The MAC passthough address is read from ACPI.
>>>> ACPI read only happens once during r8152 driver probe.
>>>> To keep the lock less time, do it after is_valid_ether_addr.
>>>>   
>>>>>
>>>>> Henning
>>>>>       
>>>>>>> +		}
>>>>>>> +	}
>>>>>>> +	rcu_read_unlock();
>>>>>>
>>>>>> Not sure if this function is guaranteed to only run once at a
>>>>>> time, otherwise i think that is a race. Multiple instances could
>>>>>> make it to this very point at the same time.
>>>>>>      
>>>>
>>>> Run once for one device.
>>>> So add a safe lock.
>>>>
>>>> Aaron
>>>>   
>>>>>> Henning
>>>>>>      
>>>>>>>     	memcpy(sa->sa_data, buf, 6);
>>>>>>>     	netif_info(tp, probe, tp->netdev,
>>>>>>>     		   "Using pass-thru MAC addr %pM\n",
>>>>>>> sa->sa_data);
>>>>>>      
>>>>>       
>>>    
>