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BUG: KCSAN: data-race in do_ipv6_setsockopt.isra.0 / udpv6_recvmsg

write to 0xffff8880a6f8ff6c of 2 bytes by task 22303 on cpu 1:
 do_ipv6_setsockopt.isra.0+0x9d6/0x2d10 net/ipv6/ipv6_sockglue.c:292
 ipv6_setsockopt+0xce/0x130 net/ipv6/ipv6_sockglue.c:950
 udpv6_setsockopt+0x67/0xb0 net/ipv6/udp.c:1567
 sock_common_setsockopt+0x5d/0x80 net/core/sock.c:3172
 __sys_setsockopt+0x1d6/0x380 net/socket.c:2132
 __do_sys_setsockopt net/socket.c:2148 [inline]
 __se_sys_setsockopt net/socket.c:2145 [inline]
 __x64_sys_setsockopt+0x6b/0x80 net/socket.c:2145
 do_syscall_64+0xc7/0x3b0 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8880a6f8ff6c of 2 bytes by task 22311 on cpu 0:
 udpv6_recvmsg+0x76d/0xf00 net/ipv6/udp.c:366
 inet6_recvmsg+0xc1/0x250 net/ipv6/af_inet6.c:593
 sock_recvmsg_nosec net/socket.c:886 [inline]
 ____sys_recvmsg+0x343/0x350 net/socket.c:2583
 ___sys_recvmsg+0xb2/0x100 net/socket.c:2627
 do_recvmmsg+0x17a/0x540 net/socket.c:2725
 __sys_recvmmsg+0x1f1/0x200 net/socket.c:2804
 __do_sys_recvmmsg net/socket.c:2827 [inline]
 __se_sys_recvmmsg net/socket.c:2820 [inline]
 __x64_sys_recvmmsg+0x82/0xb0 net/socket.c:2820
 do_syscall_64+0xc7/0x3b0 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 22311 Comm: syz-executor.0 Not tainted 5.7.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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