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BUG: KCSAN: data-race in udp_tunnel6_xmit_skb / udp_tunnel6_xmit_skb

write to 0xffff888016a0f130 of 8 bytes by task 9896 on cpu 1:
 iptunnel_xmit_stats include/net/ip_tunnels.h:456 [inline]
 ip6tunnel_xmit include/net/ip6_tunnel.h:165 [inline]
 udp_tunnel6_xmit_skb+0x42d/0x490 net/ipv6/ip6_udp_tunnel.c:109
 send6+0x2d8/0x3a0 drivers/net/wireguard/socket.c:152
 wg_socket_send_skb_to_peer+0xbb/0x130 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:2275
 worker_thread+0x616/0xa70 kernel/workqueue.c:2421
 kthread+0x20b/0x230 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296

read to 0xffff888016a0f130 of 8 bytes by task 28536 on cpu 0:
 iptunnel_xmit_stats include/net/ip_tunnels.h:456 [inline]
 ip6tunnel_xmit include/net/ip6_tunnel.h:165 [inline]
 udp_tunnel6_xmit_skb+0x41b/0x490 net/ipv6/ip6_udp_tunnel.c:109
 send6+0x2d8/0x3a0 drivers/net/wireguard/socket.c:152
 wg_socket_send_skb_to_peer+0xbb/0x130 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:2275
 worker_thread+0x616/0xa70 kernel/workqueue.c:2421
 kthread+0x20b/0x230 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: 28536 Comm: kworker/0:2 Not tainted 5.11.0-rc6-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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