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BUG: KCSAN: data-race in netlink_setsockopt / netlink_unicast

write to 0xffff88812c8e12ec of 4 bytes by task 16355 on cpu 0:
 netlink_setsockopt+0x541/0x7b0 net/netlink/af_netlink.c:1720
 __sys_setsockopt+0x18f/0x200 net/socket.c:2117
 __do_sys_setsockopt net/socket.c:2128 [inline]
 __se_sys_setsockopt net/socket.c:2125 [inline]
 __x64_sys_setsockopt+0x62/0x70 net/socket.c:2125
 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff88812c8e12ec of 4 bytes by task 16359 on cpu 1:
 netlink_is_kernel net/netlink/af_netlink.c:85 [inline]
 netlink_deliver_tap_kernel net/netlink/af_netlink.c:342 [inline]
 netlink_unicast_kernel net/netlink/af_netlink.c:1311 [inline]
 netlink_unicast+0x58f/0x6b0 net/netlink/af_netlink.c:1338
 netlink_sendmsg+0x6f8/0x7c0 net/netlink/af_netlink.c:1927
 sock_sendmsg_nosec net/socket.c:654 [inline]
 sock_sendmsg net/socket.c:674 [inline]
 sock_write_iter+0x1a4/0x200 net/socket.c:1001
 call_write_iter include/linux/fs.h:2116 [inline]
 new_sync_write fs/read_write.c:518 [inline]
 vfs_write+0x69d/0x770 fs/read_write.c:605
 ksys_write+0xce/0x180 fs/read_write.c:658
 __do_sys_write fs/read_write.c:670 [inline]
 __se_sys_write fs/read_write.c:667 [inline]
 __x64_sys_write+0x3e/0x50 fs/read_write.c:667
 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 16359 Comm: syz-executor.4 Tainted: G        W         5.12.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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