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BUG: KCSAN: data-race in __neigh_event_send / neigh_resolve_output

write to 0xffff88802385ae85 of 1 bytes by task 3153 on cpu 0:
 __neigh_event_send+0x40c/0xac0 net/core/neighbour.c:1126
 neigh_event_send include/net/neighbour.h:443 [inline]
 neigh_resolve_output+0x104/0x410 net/core/neighbour.c:1473
 neigh_output include/net/neighbour.h:509 [inline]
 ip_finish_output2+0x8e6/0xba0 net/ipv4/ip_output.c:230
 __ip_finish_output+0x3d8/0x430 net/ipv4/ip_output.c:308
 ip_finish_output+0x39/0x160 net/ipv4/ip_output.c:318
 NF_HOOK_COND include/linux/netfilter.h:290 [inline]
 ip_output+0xf6/0x1a0 net/ipv4/ip_output.c:432
 dst_output include/net/dst.h:443 [inline]
 ip_local_out+0x60/0x80 net/ipv4/ip_output.c:126
 iptunnel_xmit+0x31a/0x460 net/ipv4/ip_tunnel_core.c:82
 udp_tunnel_xmit_skb+0x15d/0x170 net/ipv4/udp_tunnel_core.c:190
 send4+0x386/0x530 drivers/net/wireguard/socket.c:85
 wg_socket_send_skb_to_peer drivers/net/wireguard/socket.c:174 [inline]
 wg_socket_send_buffer_to_peer+0x13c/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 to 0xffff88802385ae85 of 1 bytes by task 12334 on cpu 1:
 neigh_event_send include/net/neighbour.h:442 [inline]
 neigh_resolve_output+0x6f/0x410 net/core/neighbour.c:1473
 neigh_output include/net/neighbour.h:509 [inline]
 ip_finish_output2+0x8e6/0xba0 net/ipv4/ip_output.c:230
 __ip_finish_output+0x3d8/0x430 net/ipv4/ip_output.c:308
 ip_finish_output+0x39/0x160 net/ipv4/ip_output.c:318
 NF_HOOK_COND include/linux/netfilter.h:290 [inline]
 ip_output+0xf6/0x1a0 net/ipv4/ip_output.c:432
 dst_output include/net/dst.h:443 [inline]
 ip_local_out+0x60/0x80 net/ipv4/ip_output.c:126
 iptunnel_xmit+0x31a/0x460 net/ipv4/ip_tunnel_core.c:82
 udp_tunnel_xmit_skb+0x15d/0x170 net/ipv4/udp_tunnel_core.c:190
 send4+0x386/0x530 drivers/net/wireguard/socket.c:85
 wg_socket_send_skb_to_peer drivers/net/wireguard/socket.c:174 [inline]
 wg_socket_send_buffer_to_peer+0x13c/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

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 12334 Comm: kworker/u4:6 Not tainted 5.9.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: wg-kex-wg2 wg_packet_handshake_send_worker
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