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BUG: KCSAN: data-race in ipv6_setsockopt / udpv6_sendmsg

write to 0xffff88813f170f6e of 2 bytes by task 4621 on cpu 1:
 ipv6_setsockopt+0x17e5/0x3850 net/ipv6/ipv6_sockglue.c:1012
 udpv6_setsockopt+0x85/0x90 net/ipv6/udp.c:1647
 sock_common_setsockopt+0x5d/0x70 net/core/sock.c:3478
 __sys_setsockopt+0x209/0x2a0 net/socket.c:2176
 __do_sys_setsockopt net/socket.c:2187 [inline]
 __se_sys_setsockopt net/socket.c:2184 [inline]
 __x64_sys_setsockopt+0x62/0x70 net/socket.c:2184
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff88813f170f6e of 2 bytes by task 4622 on cpu 0:
 udpv6_sendmsg+0x5cb/0x16e0 net/ipv6/udp.c:1401
 inet6_sendmsg+0x5f/0x80 net/ipv6/af_inet6.c:644
 sock_sendmsg_nosec net/socket.c:704 [inline]
 sock_sendmsg net/socket.c:724 [inline]
 ____sys_sendmsg+0x39a/0x510 net/socket.c:2409
 ___sys_sendmsg net/socket.c:2463 [inline]
 __sys_sendmmsg+0x267/0x4c0 net/socket.c:2549
 __do_sys_sendmmsg net/socket.c:2578 [inline]
 __se_sys_sendmmsg net/socket.c:2575 [inline]
 __x64_sys_sendmmsg+0x53/0x60 net/socket.c:2575
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x2008 -> 0x3808

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 4622 Comm: syz-executor.2 Tainted: G        W         5.16.0-rc8-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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