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BUG: KCSAN: data-race in iptunnel_xmit / iptunnel_xmit

read-write to 0xffff888137fa5168 of 8 bytes by task 1846 on cpu 1:
 iptunnel_xmit_stats include/net/ip_tunnels.h:477 [inline]
 iptunnel_xmit+0x405/0x470 net/ipv4/ip_tunnel_core.c:87
 udp_tunnel_xmit_skb+0x15d/0x170 net/ipv4/udp_tunnel_core.c:172
 send4+0x439/0x500 drivers/net/wireguard/socket.c:85
 wg_socket_send_skb_to_peer+0x92/0x120 drivers/net/wireguard/socket.c:175
 wg_socket_send_buffer_to_peer+0xd2/0xf0 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+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

read-write to 0xffff888137fa5168 of 8 bytes by task 25067 on cpu 0:
 iptunnel_xmit_stats include/net/ip_tunnels.h:477 [inline]
 iptunnel_xmit+0x405/0x470 net/ipv4/ip_tunnel_core.c:87
 udp_tunnel_xmit_skb+0x15d/0x170 net/ipv4/udp_tunnel_core.c:172
 send4+0x439/0x500 drivers/net/wireguard/socket.c:85
 wg_socket_send_skb_to_peer+0x92/0x120 drivers/net/wireguard/socket.c:175
 wg_socket_send_buffer_to_peer+0xd2/0xf0 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+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

value changed: 0x0000000000000078 -> 0x0000000000000079

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 25067 Comm: kworker/u4:10 Not tainted 6.0.0-rc5-syzkaller-00025-g3245cb65fd91-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/26/2022
Workqueue: wg-kex-wg1 wg_packet_handshake_send_worker
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