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BUG: KCSAN: data-race in __perf_event_overflow / fasync_remove_entry

write to 0xffff8881137f3b00 of 8 bytes by task 20948 on cpu 1:
 fasync_remove_entry+0xb7/0x120 fs/fcntl.c:882
 fasync_helper+0xc9/0xd6 fs/fcntl.c:981
 perf_fasync+0x64/0x90 kernel/events/core.c:6011
 __fput+0x448/0x4f0 fs/file_table.c:277
 ____fput+0x1b/0x30 fs/file_table.c:313
 task_work_run+0xf5/0x130 kernel/task_work.c:113
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_usermode_loop+0x2ae/0x2c0 arch/x86/entry/common.c:164
 prepare_exit_to_usermode arch/x86/entry/common.c:195 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:278 [inline]
 do_syscall_64+0x36e/0x390 arch/x86/entry/common.c:304
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8881137f3b00 of 8 bytes by interrupt on cpu 0:
 __perf_event_overflow+0x116/0x200 kernel/events/core.c:8438
 perf_swevent_hrtimer+0x261/0x280 kernel/events/core.c:9822
 __run_hrtimer kernel/time/hrtimer.c:1517 [inline]
 __hrtimer_run_queues+0x271/0x600 kernel/time/hrtimer.c:1579
 hrtimer_interrupt+0x226/0x490 kernel/time/hrtimer.c:1641
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1119 [inline]
 smp_apic_timer_interrupt+0xd8/0x270 arch/x86/kernel/apic/apic.c:1144
 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:829
 arch_local_irq_restore arch/x86/include/asm/paravirt.h:752 [inline]
 kmem_cache_free+0x84/0x1f0 mm/slab.c:3699
 kfree_skbmem+0x10d/0x1a0 net/core/skbuff.c:624
 __kfree_skb net/core/skbuff.c:681 [inline]
 consume_skb net/core/skbuff.c:839 [inline]
 consume_skb+0x94/0x1f0 net/core/skbuff.c:833
 netlink_broadcast_filtered+0x262/0x9a0 net/netlink/af_netlink.c:1512
 netlink_broadcast net/netlink/af_netlink.c:1534 [inline]
 nlmsg_multicast include/net/netlink.h:968 [inline]
 nlmsg_notify+0x7e/0x200 net/netlink/af_netlink.c:2520
 rtnl_notify net/core/rtnetlink.c:737 [inline]
 rtmsg_ifinfo_send net/core/rtnetlink.c:3707 [inline]
 rtmsg_ifinfo_event.part.0+0x9a/0xc0 net/core/rtnetlink.c:3722
 rtmsg_ifinfo_event net/core/rtnetlink.c:3730 [inline]
 rtmsg_ifinfo+0x78/0x80 net/core/rtnetlink.c:3728
 register_netdevice+0x506/0xad0 net/core/dev.c:9425
 __ip_tunnel_create+0x20c/0x3f0 net/ipv4/ip_tunnel.c:269
 ip_tunnel_init_net+0x24d/0x3d1 net/ipv4/ip_tunnel.c:1060
 erspan_init_net+0x3c/0x50 net/ipv4/ip_gre.c:1594
 ops_init+0x8b/0x240 net/core/net_namespace.c:137
 setup_net+0x195/0x4b0 net/core/net_namespace.c:327
 copy_net_ns+0x1db/0x400 net/core/net_namespace.c:468
 create_new_namespaces+0x2a8/0x6a0 kernel/nsproxy.c:108
 unshare_nsproxy_namespaces+0xb5/0x170 kernel/nsproxy.c:229
 ksys_unshare+0x2e0/0x700 kernel/fork.c:2966
 __do_sys_unshare kernel/fork.c:3034 [inline]
 __se_sys_unshare kernel/fork.c:3032 [inline]
 __x64_sys_unshare+0x25/0x40 kernel/fork.c:3032
 do_syscall_64+0xc7/0x390 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 20949 Comm: syz-executor.1 Not tainted 5.6.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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