KCSAN reported multiple cpus can update use_time
at the same time.

Adds READ_ONCE()/WRITE_ONCE() annotations.

Note that 32bit arches are not fully protected,
but they will probably no longer be supported/used in 2106.

BUG: KCSAN: data-race in __xfrm_policy_check / __xfrm_policy_check

write to 0xffff88813e7ec108 of 8 bytes by interrupt on cpu 0:
__xfrm_policy_check+0x6ae/0x17f0 net/xfrm/xfrm_policy.c:3664
__xfrm_policy_check2 include/net/xfrm.h:1174 [inline]
xfrm_policy_check include/net/xfrm.h:1179 [inline]
xfrm6_policy_check+0x2e9/0x320 include/net/xfrm.h:1189
udpv6_queue_rcv_one_skb+0x48/0xa30 net/ipv6/udp.c:703
udpv6_queue_rcv_skb+0x2d6/0x310 net/ipv6/udp.c:792
udp6_unicast_rcv_skb+0x16b/0x190 net/ipv6/udp.c:935
__udp6_lib_rcv+0x84b/0x9b0 net/ipv6/udp.c:1020
udpv6_rcv+0x4b/0x50 net/ipv6/udp.c:1133
ip6_protocol_deliver_rcu+0x99e/0x1020 net/ipv6/ip6_input.c:439
ip6_input_finish net/ipv6/ip6_input.c:484 [inline]
NF_HOOK include/linux/netfilter.h:302 [inline]
ip6_input+0xca/0x180 net/ipv6/ip6_input.c:493
dst_input include/net/dst.h:454 [inline]
ip6_rcv_finish+0x1e9/0x2d0 net/ipv6/ip6_input.c:79
NF_HOOK include/linux/netfilter.h:302 [inline]
ipv6_rcv+0x85/0x140 net/ipv6/ip6_input.c:309
__netif_receive_skb_one_core net/core/dev.c:5482 [inline]
__netif_receive_skb+0x8b/0x1b0 net/core/dev.c:5596
process_backlog+0x23f/0x3b0 net/core/dev.c:5924
__napi_poll+0x65/0x390 net/core/dev.c:6485
napi_poll net/core/dev.c:6552 [inline]
net_rx_action+0x37e/0x730 net/core/dev.c:6663
__do_softirq+0xf2/0x2c7 kernel/softirq.c:571
do_softirq+0xb1/0xf0 kernel/softirq.c:472
__local_bh_enable_ip+0x6f/0x80 kernel/softirq.c:396
__raw_read_unlock_bh include/linux/rwlock_api_smp.h:257 [inline]
_raw_read_unlock_bh+0x17/0x20 kernel/locking/spinlock.c:284
wg_socket_send_skb_to_peer+0x107/0x120 drivers/net/wireguard/socket.c:184
wg_packet_create_data_done drivers/net/wireguard/send.c:251 [inline]
wg_packet_tx_worker+0x142/0x360 drivers/net/wireguard/send.c:276
process_one_work+0x3d3/0x720 kernel/workqueue.c:2289
worker_thread+0x618/0xa70 kernel/workqueue.c:2436
kthread+0x1a9/0x1e0 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308

write to 0xffff88813e7ec108 of 8 bytes by interrupt on cpu 1:
__xfrm_policy_check+0x6ae/0x17f0 net/xfrm/xfrm_policy.c:3664
__xfrm_policy_check2 include/net/xfrm.h:1174 [inline]
xfrm_policy_check include/net/xfrm.h:1179 [inline]
xfrm6_policy_check+0x2e9/0x320 include/net/xfrm.h:1189
udpv6_queue_rcv_one_skb+0x48/0xa30 net/ipv6/udp.c:703
udpv6_queue_rcv_skb+0x2d6/0x310 net/ipv6/udp.c:792
udp6_unicast_rcv_skb+0x16b/0x190 net/ipv6/udp.c:935
__udp6_lib_rcv+0x84b/0x9b0 net/ipv6/udp.c:1020
udpv6_rcv+0x4b/0x50 net/ipv6/udp.c:1133
ip6_protocol_deliver_rcu+0x99e/0x1020 net/ipv6/ip6_input.c:439
ip6_input_finish net/ipv6/ip6_input.c:484 [inline]
NF_HOOK include/linux/netfilter.h:302 [inline]
ip6_input+0xca/0x180 net/ipv6/ip6_input.c:493
dst_input include/net/dst.h:454 [inline]
ip6_rcv_finish+0x1e9/0x2d0 net/ipv6/ip6_input.c:79
NF_HOOK include/linux/netfilter.h:302 [inline]
ipv6_rcv+0x85/0x140 net/ipv6/ip6_input.c:309
__netif_receive_skb_one_core net/core/dev.c:5482 [inline]
__netif_receive_skb+0x8b/0x1b0 net/core/dev.c:5596
process_backlog+0x23f/0x3b0 net/core/dev.c:5924
__napi_poll+0x65/0x390 net/core/dev.c:6485
napi_poll net/core/dev.c:6552 [inline]
net_rx_action+0x37e/0x730 net/core/dev.c:6663
__do_softirq+0xf2/0x2c7 kernel/softirq.c:571
do_softirq+0xb1/0xf0 kernel/softirq.c:472
__local_bh_enable_ip+0x6f/0x80 kernel/softirq.c:396
__raw_read_unlock_bh include/linux/rwlock_api_smp.h:257 [inline]
_raw_read_unlock_bh+0x17/0x20 kernel/locking/spinlock.c:284
wg_socket_send_skb_to_peer+0x107/0x120 drivers/net/wireguard/socket.c:184
wg_packet_create_data_done drivers/net/wireguard/send.c:251 [inline]
wg_packet_tx_worker+0x142/0x360 drivers/net/wireguard/send.c:276
process_one_work+0x3d3/0x720 kernel/workqueue.c:2289
worker_thread+0x618/0xa70 kernel/workqueue.c:2436
kthread+0x1a9/0x1e0 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308

value changed: 0x0000000063c62d6f -> 0x0000000063c62d70

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 4185 Comm: kworker/1:2 Tainted: G W 6.2.0-rc4-syzkaller-00009-gd532dd10-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
Workqueue: wg-crypt-wg0 wg_packet_tx_worker

Fixes: 1da177e4 ("Linux-2.6.12-rc2")
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Steffen Klassert <steffen.klassert@secunet.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>