GitLab

commit 4789a218

 ("s390/qeth: fix race when setting MAC address")
resolved a race where our initial programming of dev_addr into the HW
and a call to ndo_set_mac_address() could run concurrently. In this
case, we could end up getting confused about which address was actually
set in the HW.

The quick fix was to introduce additional locking that blocks any
ndo_set_mac_address() while the device is being set online. But the race
primarily originated from the fact that we first register the netdevice,
and only then program its dev_addr. By re-ordering this sequence,
userspace will only be able to change the MAC address _after_ we have
finished with setting the initial dev_addr.

Still, the same MAC address race can also occur during a subsequent call
to qeth_l2_set_online(). So keep around the locking for now, until a
follow-up patch fully resolves this.
Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>