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BUG: KCSAN: data-race in prandom_seed / prandom_u32

read to 0xffff888237d28848 of 8 bytes by task 1905 on cpu 0:
 prandom_seed+0xbb/0x270 lib/random32.c:439
 addrconf_dad_begin net/ipv6/addrconf.c:3975 [inline]
 addrconf_dad_work+0x265/0xbb0 net/ipv6/addrconf.c:4100
 process_one_work+0x3d3/0x720 kernel/workqueue.c:2289
 worker_thread+0x618/0xa70 kernel/workqueue.c:2436
 kthread+0x1a9/0x1e0 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30

write to 0xffff888237d28848 of 8 bytes by task 1829 on cpu 1:
 siprand_u32 lib/random32.c:372 [inline]
 prandom_u32+0x10e/0x190 lib/random32.c:387
 prandom_u32_max include/linux/prandom.h:96 [inline]
 ip_idents_reserve net/ipv4/route.c:474 [inline]
 __ip_select_ident+0x12d/0x190 net/ipv4/route.c:496
 iptunnel_xmit+0x2f6/0x490 net/ipv4/ip_tunnel_core.c:80
 udp_tunnel_xmit_skb+0x15d/0x170 net/ipv4/udp_tunnel_core.c:171
 send4+0x439/0x500 drivers/net/wireguard/socket.c:85
 wg_socket_send_skb_to_peer+0x92/0x120 drivers/net/wireguard/socket.c:175
 wg_socket_send_buffer_to_peer+0xd2/0xf0 drivers/net/wireguard/socket.c:200
 wg_packet_send_handshake_initiation drivers/net/wireguard/send.c:40 [inline]
 wg_packet_handshake_send_worker+0x109/0x150 drivers/net/wireguard/send.c:51
 process_one_work+0x3d3/0x720 kernel/workqueue.c:2289
 worker_thread+0x618/0xa70 kernel/workqueue.c:2436
 kthread+0x1a9/0x1e0 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30

value changed: 0xeb4de494f1325140 -> 0x78d517bb7769ef6a

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 1829 Comm: kworker/u4:3 Not tainted 5.18.0-rc7-syzkaller-00006-g210e04ff7681-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: wg-kex-wg1 wg_packet_handshake_send_worker

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