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BUG: KCSAN: data-race in ip_vs_add_service / ip_vs_out_hook

write to 0xffff8881199a9004 of 4 bytes by task 13277 on cpu 1:
 ip_vs_add_service+0xa18/0xa70 net/netfilter/ipvs/ip_vs_ctl.c:1488
 do_ip_vs_set_ctl+0x6ec/0x8c0 net/netfilter/ipvs/ip_vs_ctl.c:2808
 nf_setsockopt+0x199/0x1b0 net/netfilter/nf_sockopt.c:101
 ip_setsockopt+0x102/0x110 net/ipv4/ip_sockglue.c:1424
 udp_setsockopt+0x99/0xb0 net/ipv4/udp.c:3081
 sock_common_setsockopt+0x69/0x80 net/core/sock.c:3903
 do_sock_setsockopt net/socket.c:2344 [inline]
 __sys_setsockopt+0x181/0x200 net/socket.c:2369
 __do_sys_setsockopt net/socket.c:2375 [inline]
 __se_sys_setsockopt net/socket.c:2372 [inline]
 __x64_sys_setsockopt+0x64/0x80 net/socket.c:2372
 x64_sys_call+0x20ec/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:55
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff8881199a9004 of 4 bytes by task 13269 on cpu 0:
 ip_vs_out_hook+0x1c1/0x920 net/netfilter/ipvs/ip_vs_core.c:1356
 nf_hook_entry_hookfn include/linux/netfilter.h:158 [inline]
 nf_hook_slow+0x78/0x180 net/netfilter/core.c:623
 nf_hook include/linux/netfilter.h:273 [inline]
 __ip_local_out+0x2cb/0x2f0 net/ipv4/ip_output.c:118
 ip_local_out net/ipv4/ip_output.c:127 [inline]
 ip_send_skb+0x34/0x160 net/ipv4/ip_output.c:1506
 udp_send_skb+0x6e3/0xa40 net/ipv4/udp.c:1195
 udp_sendmsg+0x1050/0x13c0 net/ipv4/udp.c:1484
 inet_sendmsg+0xac/0xd0 net/ipv4/af_inet.c:851
 sock_sendmsg_nosec net/socket.c:714 [inline]
 __sock_sendmsg+0x102/0x180 net/socket.c:729
 ____sys_sendmsg+0x345/0x4e0 net/socket.c:2614
 ___sys_sendmsg+0x17b/0x1d0 net/socket.c:2668
 __sys_sendmmsg+0x178/0x300 net/socket.c:2757
 __do_sys_sendmmsg net/socket.c:2784 [inline]
 __se_sys_sendmmsg net/socket.c:2781 [inline]
 __x64_sys_sendmmsg+0x57/0x70 net/socket.c:2781
 x64_sys_call+0x1c4a/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:308
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000000 -> 0x00000001

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 13269 Comm: syz.0.3422 Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
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IPVS: wlc: UDP 224.0.0.2:0 - no destination available