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BUG: KCSAN: data-race in __neigh_event_send / neigh_resolve_output

write to 0xffff88801f073885 of 1 bytes by task 3184 on cpu 1:
 __neigh_event_send+0x40c/0xad0 net/core/neighbour.c:1128
 neigh_event_send include/net/neighbour.h:444 [inline]
 neigh_resolve_output+0x104/0x410 net/core/neighbour.c:1476
 neigh_output include/net/neighbour.h:510 [inline]
 ip6_finish_output2+0x985/0xb20 net/ipv6/ip6_output.c:117
 __ip6_finish_output+0x428/0x480 net/ipv6/ip6_output.c:182
 ip6_finish_output+0x39/0x160 net/ipv6/ip6_output.c:192
 NF_HOOK_COND include/linux/netfilter.h:290 [inline]
 ip6_output+0x10e/0x210 net/ipv6/ip6_output.c:215
 dst_output include/net/dst.h:441 [inline]
 ip6_local_out+0x60/0x80 net/ipv6/output_core.c:179
 ip6tunnel_xmit include/net/ip6_tunnel.h:160 [inline]
 udp_tunnel6_xmit_skb+0x2f9/0x490 net/ipv6/ip6_udp_tunnel.c:109
 send6+0x2d8/0x3a0 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+0x186/0x210 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: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 0xffff88801f073885 of 1 bytes by task 13760 on cpu 0:
 neigh_event_send include/net/neighbour.h:443 [inline]
 neigh_resolve_output+0x6f/0x410 net/core/neighbour.c:1476
 neigh_output include/net/neighbour.h:510 [inline]
 ip6_finish_output2+0x985/0xb20 net/ipv6/ip6_output.c:117
 __ip6_finish_output+0x428/0x480 net/ipv6/ip6_output.c:182
 ip6_finish_output+0x39/0x160 net/ipv6/ip6_output.c:192
 NF_HOOK_COND include/linux/netfilter.h:290 [inline]
 ip6_output+0x10e/0x210 net/ipv6/ip6_output.c:215
 dst_output include/net/dst.h:441 [inline]
 ip6_local_out+0x60/0x80 net/ipv6/output_core.c:179
 ip6tunnel_xmit include/net/ip6_tunnel.h:160 [inline]
 udp_tunnel6_xmit_skb+0x2f9/0x490 net/ipv6/ip6_udp_tunnel.c:109
 send6+0x2d8/0x3a0 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+0x186/0x210 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: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: 13760 Comm: kworker/u4:6 Not tainted 5.11.0-rc6-syzkaller #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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