[SRU Focal,Focal/oem-5.6,Groovy] CVE-2020-14386

[Thadeu Lima de Souza Cascardo]

[Impact]
Unprivileged user can crash the system using user namespaces and packet
sockets.

[Test case] A PoC that crashes the system has been available at [1]. It has
been used to test this, after changing 'ifconfig lo up', to 'ip link set lo up'.

[1] https://www.openwall.com/lists/oss-security/2020/09/03/3

[Potential regression]
AF_PACKET could be broken by this.