linux-kernel - Re: [PATCH] usb: gadget: u_ether: fix race in setting MAC address in setup phase

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Message-ID: <87ee6sxlcj.fsf@mutex.one>
Date:   Sat, 04 Dec 2021 20:42:52 +0200
From:   Marian Postevca <posteuca@...ex.one>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Felipe Balbi <balbi@...nel.org>, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] usb: gadget: u_ether: fix race in setting MAC address
 in setup phase

Greg Kroah-Hartman <gregkh@...uxfoundation.org> writes:

> On Tue, Nov 30, 2021 at 12:12:29AM +0200, Marian Postevca wrote:
>> When listening for notifications through netlink of a new interface being
>> registered, sporadically, it is possible for the MAC to be read as zero.
>> The zero MAC address lasts a short period of time and then switches to a
>> valid random MAC address.
>> 
>> This causes problems for netd in Android, which assumes that the interface
>> is malfunctioning and will not use it.
>> 
>> In the good case we get this log:
>> InterfaceController::getCfg() ifName usb0
>>  hwAddr 92:a8:f0:73:79:5b ipv4Addr 0.0.0.0 flags 0x1002
>> 
>> In the error case we get these logs:
>> InterfaceController::getCfg() ifName usb0
>>  hwAddr 00:00:00:00:00:00 ipv4Addr 0.0.0.0 flags 0x1002
>> 
>> netd : interfaceGetCfg("usb0")
>> netd : interfaceSetCfg() -> ServiceSpecificException
>>  (99, "[Cannot assign requested address] : ioctl() failed")
>> 
>> The reason for the issue is the order in which the interface is setup,
>> it is first registered through register_netdev() and after the MAC
>> address is set.
>> 
>> Fixed by first setting the MAC address of the net_device and after that
>> calling register_netdev().
>> 
>> Signed-off-by: Marian Postevca <posteuca@...ex.one>
>> ---
>>  drivers/usb/gadget/function/u_ether.c | 16 ++++++----------
>>  1 file changed, 6 insertions(+), 10 deletions(-)
>
> What commit does this fix?  Should it go to stable kernel releases?
>
> thanks,
>
> greg k-h

This fixes bcd4a1c40bee885e ("usb: gadget: u_ether: construct with
default values and add setters/getters").

I think it should go to stable kernel releases.

Should I send a second version of the patch with a Fixes tag?

Thanks