CVE-2021-47223

In the Linux kernel, the following vulnerability has been resolved: net:
bridge: fix vlan tunnel dst null pointer dereference This patch fixes a
tunnel_dst null pointer dereference due to lockless access in the tunnel
egress path. When deleting a vlan tunnel the tunnel_dst pointer is set to
NULL without waiting a grace period (i.e. while it’s still usable) and
packets egressing are dereferencing it without checking. Use
READ/WRITE_ONCE to annotate the lockless use of tunnel_id, use RCU for
accessing tunnel_dst and make sure it is read only once and checked in the
egress path. The dst is already properly RCU protected so we don’t need to
do anything fancy than to make sure tunnel_id and tunnel_dst are read only
once and checked in the egress path.