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

[Aaron Ma]

On 1/5/22 15:32, Henning Schild wrote:
> Am Wed, 5 Jan 2022 08:23:55 +0100
> schrieb Henning Schild <henning.schild@xxxxxxxxxxx>:
>
> > 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@xxxxxxxxxxxxx>:
> >
> > > 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@xxxxxxxxxxxxx>
> > > ---
> > >   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.

> > 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);
> > >