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BUG: KCSAN: data-race in __netlink_dump_start / netlink_recvmsg

write to 0xffff8881247e7b41 of 1 bytes by task 12923 on cpu 1:
 __netlink_dump_start+0x3a5/0x4d0 net/netlink/af_netlink.c:2348
 netlink_dump_start include/linux/netlink.h:246 [inline]
 rtnetlink_rcv_msg+0x6c3/0x7b0 net/core/rtnetlink.c:5423
 netlink_rcv_skb+0x13e/0x240 net/netlink/af_netlink.c:2469
 rtnetlink_rcv+0x18/0x20 net/core/rtnetlink.c:5478
 netlink_unicast_kernel net/netlink/af_netlink.c:1303 [inline]
 netlink_unicast+0x5e2/0x6b0 net/netlink/af_netlink.c:1329
 netlink_sendmsg+0x6d8/0x7a0 net/netlink/af_netlink.c:1918
 sock_sendmsg_nosec net/socket.c:652 [inline]
 sock_sendmsg net/socket.c:672 [inline]
 ____sys_sendmsg+0x360/0x4d0 net/socket.c:2352
 ___sys_sendmsg net/socket.c:2406 [inline]
 __sys_sendmsg+0x1df/0x260 net/socket.c:2439
 __do_sys_sendmsg net/socket.c:2448 [inline]
 __se_sys_sendmsg net/socket.c:2446 [inline]
 __x64_sys_sendmsg+0x42/0x50 net/socket.c:2446
 do_syscall_64+0x51/0xb0 arch/x86/entry/common.c:359
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8881247e7b41 of 1 bytes by task 12929 on cpu 0:
 netlink_recvmsg+0x3f0/0x7b0 net/netlink/af_netlink.c:1999
 ____sys_recvmsg+0x15a/0x2e0 include/linux/uio.h:235
 ___sys_recvmsg net/socket.c:2617 [inline]
 do_recvmmsg+0x35c/0xa30 net/socket.c:2715
 __sys_recvmmsg net/socket.c:2794 [inline]
 __do_sys_recvmmsg net/socket.c:2817 [inline]
 __se_sys_recvmmsg net/socket.c:2810 [inline]
 __x64_sys_recvmmsg+0xcc/0x150 net/socket.c:2810
 do_syscall_64+0x51/0xb0 arch/x86/entry/common.c:359
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 12929 Comm: syz-executor.1 Not tainted 5.8.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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