CVE-2021-47164

In the Linux kernel, the following vulnerability has been resolved:
net/mlx5e: Fix null deref accessing lag dev It could be the lag dev is null
so stop processing the event. In bond_enslave() the active/backup slave
being set before setting the upper dev so first event is without an upper
dev. After setting the upper dev with bond_master_upper_dev_link() there is
a second event and in that event we have an upper dev.