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

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Date:   Sat, 4 Dec 2021 19:47:40 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Marian Postevca <posteuca@...ex.one>
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

On Sat, Dec 04, 2021 at 08:42:52PM +0200, Marian Postevca wrote:
> 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?

Yes please, and a cc: stable on the line after the fixes tag.

thanks,

greg k-h