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BUG: KCSAN: data-race in __ip6_datagram_connect / udpv6_sendmsg

read to 0xffff888104502138 of 8 bytes by task 16770 on cpu 1:
 ipv6_addr_v4mapped include/net/ipv6.h:777 [inline]
 udpv6_sendmsg+0x39c/0x1590 net/ipv6/udp.c:1533
 inet6_sendmsg+0xac/0xd0 net/ipv6/af_inet6.c:659
 sock_sendmsg_nosec net/socket.c:714 [inline]
 __sock_sendmsg+0x8b/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

write to 0xffff888104502138 of 16 bytes by task 16773 on cpu 0:
 __ip6_datagram_connect+0x6d1/0x7e0 net/ipv6/datagram.c:246
 udpv6_connect+0x33/0x150 net/ipv6/udp.c:1310
 inet_dgram_connect+0x125/0x1c0 net/ipv4/af_inet.c:592
 __sys_connect_file net/socket.c:2086 [inline]
 __sys_connect+0x1f2/0x2b0 net/socket.c:2105
 __do_sys_connect net/socket.c:2111 [inline]
 __se_sys_connect net/socket.c:2108 [inline]
 __x64_sys_connect+0x3f/0x50 net/socket.c:2108
 x64_sys_call+0x2c08/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:43
 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

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 16773 Comm: syz.4.4436 Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
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