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BUG: KCSAN: data-race in __ip6_datagram_connect / udpv6_sendmsg

read to 0xffff888104ca33f8 of 8 bytes by task 7589 on cpu 0:
 ipv6_addr_v4mapped include/net/ipv6.h:777 [inline]
 udpv6_sendmsg+0x3bc/0x15b0 net/ipv6/udp.c:1535
 inet6_sendmsg+0xac/0xd0 net/ipv6/af_inet6.c:659
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg+0x8b/0x180 net/socket.c:742
 ____sys_sendmsg+0x345/0x4a0 net/socket.c:2592
 ___sys_sendmsg+0x17b/0x1d0 net/socket.c:2646
 __sys_sendmmsg+0x178/0x300 net/socket.c:2735
 __do_sys_sendmmsg net/socket.c:2762 [inline]
 __se_sys_sendmmsg net/socket.c:2759 [inline]
 __x64_sys_sendmmsg+0x57/0x70 net/socket.c:2759
 x64_sys_call+0x1e28/0x3000 arch/x86/include/generated/asm/syscalls_64.h:308
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd8/0x2c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

write to 0xffff888104ca33f8 of 16 bytes by task 7588 on cpu 1:
 __ip6_datagram_connect+0x6d1/0x7e0 net/ipv6/datagram.c:246
 udpv6_connect+0x33/0x150 net/ipv6/udp.c:1312
 inet_dgram_connect+0x125/0x1c0 net/ipv4/af_inet.c:594
 __sys_connect_file net/socket.c:2089 [inline]
 __sys_connect+0x1f2/0x2b0 net/socket.c:2108
 __do_sys_connect net/socket.c:2114 [inline]
 __se_sys_connect net/socket.c:2111 [inline]
 __x64_sys_connect+0x3f/0x50 net/socket.c:2111
 x64_sys_call+0x2e09/0x3000 arch/x86/include/generated/asm/syscalls_64.h:43
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd8/0x2c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 7588 Comm: syz.3.1335 Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
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