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BUG: KCSAN: data-race in __skb_try_recv_datagram / do_recvmmsg

write to 0xffff88812982d230 of 4 bytes by task 19527 on cpu 0:
 do_recvmmsg+0x923/0x9e0 net/socket.c:2761
 __sys_recvmmsg net/socket.c:2786 [inline]
 __do_sys_recvmmsg net/socket.c:2807 [inline]
 __se_sys_recvmmsg net/socket.c:2800 [inline]
 __x64_sys_recvmmsg+0xe6/0x150 net/socket.c:2800
 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff88812982d230 of 4 bytes by task 19535 on cpu 1:
 sock_error include/net/sock.h:2267 [inline]
 __skb_try_recv_datagram+0x47/0x310 net/core/datagram.c:252
 __skb_recv_datagram net/core/datagram.c:297 [inline]
 skb_recv_datagram+0xab/0x150 net/core/datagram.c:317
 netlink_recvmsg+0x68/0x760 net/netlink/af_netlink.c:1950
 sock_recvmsg_nosec net/socket.c:888 [inline]
 sock_recvmsg net/socket.c:906 [inline]
 __sys_recvfrom+0x1d7/0x2a0 net/socket.c:2034
 __do_sys_recvfrom net/socket.c:2052 [inline]
 __se_sys_recvfrom net/socket.c:2048 [inline]
 __x64_sys_recvfrom+0x74/0x90 net/socket.c:2048
 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: 19535 Comm: syz-executor.3 Not tainted 5.13.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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