sched: act_ct: take care of padding in struct zones_ht_key

In the Linux kernel, the following vulnerability has been resolved:

sched: act_ct: take care of padding in struct zones_ht_key

Blamed commit increased lookup key size from 2 bytes to 16 bytes,
because zones_ht_key got a struct net pointer.

Make sure rhashtable_lookup() is not using the padding bytes
which are not initialized.

BUG: KMSAN: uninit-value in rht_ptr_rcu include/linux/rhashtable.h:376 [inline]
BUG: KMSAN: uninit-value in __rhashtable_lookup include/linux/rhashtable.h:607 [inline]
BUG: KMSAN: uninit-value in rhashtable_lookup include/linux/rhashtable.h:646 [inline]
BUG: KMSAN: uninit-value in rhashtable_lookup_fast include/linux/rhashtable.h:672 [inline]
BUG: KMSAN: uninit-value in tcf_ct_flow_table_get+0x611/0x2260 net/sched/act_ct.c:329
rht_ptr_rcu include/linux/rhashtable.h:376 [inline]
__rhashtable_lookup include/linux/rhashtable.h:607 [inline]
rhashtable_lookup include/linux/rhashtable.h:646 [inline]
rhashtable_lookup_fast include/linux/rhashtable.h:672 [inline]
tcf_ct_flow_table_get+0x611/0x2260 net/sched/act_ct.c:329
tcf_ct_init+0xa67/0x2890 net/sched/act_ct.c:1408
tcf_action_init_1+0x6cc/0xb30 net/sched/act_api.c:1425
tcf_action_init+0x458/0xf00 net/sched/act_api.c:1488
tcf_action_add net/sched/act_api.c:2061 [inline]
tc_ctl_action+0x4be/0x19d0 net/sched/act_api.c:2118
rtnetlink_rcv_msg+0x12fc/0x1410 net/core/rtnetlink.c:6647
netlink_rcv_skb+0x375/0x650 net/netlink/af_netlink.c:2550
rtnetlink_rcv+0x34/0x40 net/core/rtnetlink.c:6665
netlink_unicast_kernel net/netlink/af_netlink.c:1331 [inline]
netlink_unicast+0xf52/0x1260 net/netlink/af_netlink.c:1357
netlink_sendmsg+0x10da/0x11e0 net/netlink/af_netlink.c:1901
sock_sendmsg_nosec net/socket.c:730 [inline]
__sock_sendmsg+0x30f/0x380 net/socket.c:745
____sys_sendmsg+0x877/0xb60 net/socket.c:2597
___sys_sendmsg+0x28d/0x3c0 net/socket.c:2651
__sys_sendmsg net/socket.c:2680 [inline]
__do_sys_sendmsg net/socket.c:2689 [inline]
__se_sys_sendmsg net/socket.c:2687 [inline]
__x64_sys_sendmsg+0x307/0x4a0 net/socket.c:2687
x64_sys_call+0x2dd6/0x3c10 arch/x86/include/generated/asm/syscalls_64.h:47
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcd/0x1e0 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Local variable key created at:
tcf_ct_flow_table_get+0x4a/0x2260 net/sched/act_ct.c:324
tcf_ct_init+0xa67/0x2890 net/sched/act_ct.c:1408