syzbot

==================================================================
BUG: KCSAN: data-race in __neigh_event_send / ip6_dst_lookup_tail

write to 0xffff88812da4f484 of 1 bytes by task 13431 on cpu 1:
 __neigh_event_send+0x3bd/0xa70 net/core/neighbour.c:1213
 neigh_event_send_probe include/net/neighbour.h:470 [inline]
 neigh_event_send include/net/neighbour.h:476 [inline]
 neigh_resolve_output+0x114/0x430 net/core/neighbour.c:1567
 neigh_output include/net/neighbour.h:546 [inline]
 ip6_finish_output2+0x9bc/0xc50 net/ipv6/ip6_output.c:134
 __ip6_finish_output net/ipv6/ip6_output.c:195 [inline]
 ip6_finish_output+0x39a/0x4e0 net/ipv6/ip6_output.c:206
 NF_HOOK_COND include/linux/netfilter.h:291 [inline]
 ip6_output+0xeb/0x220 net/ipv6/ip6_output.c:227
 dst_output include/net/dst.h:444 [inline]
 ip6_local_out+0x64/0x80 net/ipv6/output_core.c:155
 ip6tunnel_xmit include/net/ip6_tunnel.h:161 [inline]
 udp_tunnel6_xmit_skb+0x333/0x4c0 net/ipv6/ip6_udp_tunnel.c:109
 send6+0x2ea/0x3a0 drivers/net/wireguard/socket.c:152
 wg_socket_send_skb_to_peer+0xbd/0x130 drivers/net/wireguard/socket.c:178
 wg_socket_send_buffer_to_peer+0xd6/0x100 drivers/net/wireguard/socket.c:200
 wg_packet_send_handshake_initiation drivers/net/wireguard/send.c:40 [inline]
 wg_packet_handshake_send_worker+0x10c/0x150 drivers/net/wireguard/send.c:51
 process_one_work+0x3e6/0x750 kernel/workqueue.c:2390
 worker_thread+0x5f2/0xa10 kernel/workqueue.c:2537
 kthread+0x1ac/0x1e0 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308

read to 0xffff88812da4f484 of 1 bytes by task 13210 on cpu 0:
 ip6_dst_lookup_tail+0x747/0x930 net/ipv6/ip6_output.c:1156
 ip6_dst_lookup_flow+0x48/0xc0 net/ipv6/ip6_output.c:1240
 send6+0x238/0x3a0 drivers/net/wireguard/socket.c:139
 wg_socket_send_skb_to_peer+0xbd/0x130 drivers/net/wireguard/socket.c:178
 wg_socket_send_buffer_to_peer+0xd6/0x100 drivers/net/wireguard/socket.c:200
 wg_packet_send_handshake_initiation drivers/net/wireguard/send.c:40 [inline]
 wg_packet_handshake_send_worker+0x10c/0x150 drivers/net/wireguard/send.c:51
 process_one_work+0x3e6/0x750 kernel/workqueue.c:2390
 worker_thread+0x5f2/0xa10 kernel/workqueue.c:2537
 kthread+0x1ac/0x1e0 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308

value changed: 0x20 -> 0x01

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 13210 Comm: kworker/u4:19 Not tainted 6.3.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/02/2023
Workqueue: wg-kex-wg1 wg_packet_handshake_send_worker
==================================================================