Description: net/packet: fix overflow in tpacket_rcv
References:
 https://www.openwall.com/lists/oss-security/2020/09/03/3
 https://www.openwall.com/lists/oss-security/2020/09/04/2
 https://lore.kernel.org/netdev/CAM6JnLf_8nwzq+UGO+amXpeApCDarJjwzOEHQd5qBhU7YKm3DQ@mail.gmail.com/
 https://lore.kernel.org/netdev/20200904040528.3635711-1-edumazet@google.com/
Notes:
 carnil> To create AF_PACKET sockets one needs CAP_NET_RAW in the
 carnil> network namepsace, which could be aquired by unprivileged
 carnil> processes on systems where unprivileged namespaces are enabled.
 carnil> Debian does not enable those.
Bugs:
upstream: pending [acf69c946233259ab4d64f8869d4037a198c7f06]
4.19-upstream-stable: needed
4.9-upstream-stable: needed
sid: pending (5.8.7-1) [bugfix/all/net-packet-fix-overflow-in-tpacket_rcv.patch]
4.19-buster-security: needed
4.9-stretch-security: needed