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BUG: KCSAN: data-race in fasync_remove_entry / kill_fasync

read to 0xffff888074bebef8 of 8 bytes by interrupt on cpu 0:
 kill_fasync+0x3f/0x180 fs/fcntl.c:1019
 perf_event_wakeup+0x11f/0x160 kernel/events/core.c:5957
 perf_pending_event+0x12d/0x170 kernel/events/core.c:6013
 irq_work_run_list+0xea/0x140 kernel/irq_work.c:165
 irq_work_run+0x48/0xa0 kernel/irq_work.c:180
 smp_irq_work_interrupt+0x3f/0x100 arch/x86/kernel/irq_work.c:21
 irq_work_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:861
 __sanitizer_cov_trace_pc+0x0/0x50
 snprintf+0x6f/0xa0 lib/vsprintf.c:2643
 __dev_alloc_name net/core/dev.c:1009 [inline]
 dev_alloc_name_ns+0x1bf/0x360 net/core/dev.c:1037
 dev_get_valid_name+0x75/0xe0 net/core/dev.c:1072
 register_netdevice+0xfa/0xa50 net/core/dev.c:9010
 ipip6_tunnel_create+0x176/0x200 net/ipv6/sit.c:208
 ipip6_newlink+0xde/0x210 net/ipv6/sit.c:1589
 __rtnl_newlink+0xc89/0x1010 net/core/rtnetlink.c:3197
 rtnl_newlink+0x63/0x90 net/core/rtnetlink.c:3255
 rtnetlink_rcv_msg+0x1d3/0x500 net/core/rtnetlink.c:5224
 netlink_rcv_skb+0xb0/0x260 net/netlink/af_netlink.c:2477
 rtnetlink_rcv+0x26/0x30 net/core/rtnetlink.c:5242
 netlink_unicast_kernel net/netlink/af_netlink.c:1302 [inline]
 netlink_unicast+0x354/0x430 net/netlink/af_netlink.c:1328
 netlink_sendmsg+0x456/0x770 net/netlink/af_netlink.c:1917
 sock_sendmsg_nosec net/socket.c:637 [inline]
 sock_sendmsg+0x9f/0xc0 net/socket.c:657
 ___sys_sendmsg+0x59d/0x5d0 net/socket.c:2311
 __sys_sendmsg+0xa0/0x160 net/socket.c:2356
 __do_sys_sendmsg net/socket.c:2365 [inline]
 __se_sys_sendmsg net/socket.c:2363 [inline]
 __x64_sys_sendmsg+0x51/0x70 net/socket.c:2363
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

write to 0xffff888074bebef8 of 8 bytes by task 22841 on cpu 1:
 fasync_remove_entry+0xba/0x120 fs/fcntl.c:882
 fasync_helper+0xcf/0xdc fs/fcntl.c:981
 perf_fasync+0x6c/0xa0 kernel/events/core.c:5917
 __fput+0x46a/0x520 fs/file_table.c:277
 ____fput+0x1f/0x30 fs/file_table.c:313
 task_work_run+0xf6/0x130 kernel/task_work.c:113
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_usermode_loop+0x2b4/0x2c0 arch/x86/entry/common.c:163
 prepare_exit_to_usermode arch/x86/entry/common.c:194 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:274 [inline]
 do_syscall_64+0x353/0x370 arch/x86/entry/common.c:300
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 22841 Comm: syz-executor.2 Not tainted 5.4.0-rc7+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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