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BUG: KCSAN: data-race in udp_tunnel6_xmit_skb / udp_tunnel6_xmit_skb

read-write to 0xffff88800bf99130 of 8 bytes by task 21 on cpu 1:
 iptunnel_xmit_stats include/net/ip_tunnels.h:458 [inline]
 ip6tunnel_xmit include/net/ip6_tunnel.h:165 [inline]
 udp_tunnel6_xmit_skb+0x3cf/0x420 net/ipv6/ip6_udp_tunnel.c:109
 send6+0x2cd/0x3a0 drivers/net/wireguard/socket.c:152
 wg_socket_send_skb_to_peer drivers/net/wireguard/socket.c:177 [inline]
 wg_socket_send_buffer_to_peer+0x167/0x1e0 drivers/net/wireguard/socket.c:199
 wg_packet_send_handshake_initiation drivers/net/wireguard/send.c:40 [inline]
 wg_packet_handshake_send_worker+0xf9/0x140 drivers/net/wireguard/send.c:51
 process_one_work+0x3e1/0x950 kernel/workqueue.c:2272
 worker_thread+0x635/0xb90 kernel/workqueue.c:2418
 kthread+0x1fa/0x220 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296

read-write to 0xffff88800bf99130 of 8 bytes by task 7 on cpu 0:
 iptunnel_xmit_stats include/net/ip_tunnels.h:458 [inline]
 ip6tunnel_xmit include/net/ip6_tunnel.h:165 [inline]
 udp_tunnel6_xmit_skb+0x3cf/0x420 net/ipv6/ip6_udp_tunnel.c:109
 send6+0x2cd/0x3a0 drivers/net/wireguard/socket.c:152
 wg_socket_send_skb_to_peer+0xbb/0x120 drivers/net/wireguard/socket.c:177
 wg_packet_create_data_done drivers/net/wireguard/send.c:252 [inline]
 wg_packet_tx_worker+0x1e3/0x4c0 drivers/net/wireguard/send.c:280
 process_one_work+0x3e1/0x950 kernel/workqueue.c:2272
 worker_thread+0x635/0xb90 kernel/workqueue.c:2418
 kthread+0x1fa/0x220 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 7 Comm: kworker/0:1 Not tainted 5.10.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: wg-crypt-wg0 wg_packet_tx_worker
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