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BUG: KCSAN: data-race in udp_tunnel6_xmit_skb / udp_tunnel6_xmit_skb

read to 0xffff88813571e158 of 8 bytes by task 12963 on cpu 0:
 iptunnel_xmit_stats include/net/ip_tunnels.h:460 [inline]
 ip6tunnel_xmit include/net/ip6_tunnel.h:166 [inline]
 udp_tunnel6_xmit_skb+0x45b/0x4d0 net/ipv6/ip6_udp_tunnel.c:109
 send6+0x2f7/0x3c0 drivers/net/wireguard/socket.c:152
 wg_socket_send_skb_to_peer+0xbb/0x130 drivers/net/wireguard/socket.c:178
 wg_socket_send_buffer_to_peer+0xf7/0x120 drivers/net/wireguard/socket.c:200
 wg_packet_send_handshake_initiation drivers/net/wireguard/send.c:40 [inline]
 wg_packet_handshake_send_worker+0x109/0x150 drivers/net/wireguard/send.c:51
 process_one_work+0x3e3/0x970 kernel/workqueue.c:2289
 worker_thread+0x638/0xaa0 kernel/workqueue.c:2436
 kthread+0x1c1/0x1e0 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30

write to 0xffff88813571e158 of 8 bytes by task 16559 on cpu 1:
 iptunnel_xmit_stats include/net/ip_tunnels.h:460 [inline]
 ip6tunnel_xmit include/net/ip6_tunnel.h:166 [inline]
 udp_tunnel6_xmit_skb+0x46d/0x4d0 net/ipv6/ip6_udp_tunnel.c:109
 send6+0x2f7/0x3c0 drivers/net/wireguard/socket.c:152
 wg_socket_send_skb_to_peer+0xbb/0x130 drivers/net/wireguard/socket.c:178
 wg_socket_send_buffer_to_peer+0xf7/0x120 drivers/net/wireguard/socket.c:200
 wg_packet_send_handshake_initiation drivers/net/wireguard/send.c:40 [inline]
 wg_packet_handshake_send_worker+0x109/0x150 drivers/net/wireguard/send.c:51
 process_one_work+0x3e3/0x970 kernel/workqueue.c:2289
 worker_thread+0x638/0xaa0 kernel/workqueue.c:2436
 kthread+0x1c1/0x1e0 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30

value changed: 0x0000000000000190 -> 0x0000000000000191

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 16559 Comm: kworker/u4:3 Not tainted 5.18.0-rc1-syzkaller-00016-g3e732ebf7316-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: wg-kex-wg0 wg_packet_handshake_send_worker
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