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BUG: KCSAN: data-race in do_epoll_wait / ep_poll_callback

write to 0xffff888120d80b90 of 8 bytes by interrupt on cpu 1:
 list_add_tail_lockless fs/eventpoll.c:1158 [inline]
 ep_poll_callback+0x29c/0x510 fs/eventpoll.c:1248
 __wake_up_common+0xbc/0x130 kernel/sched/wait.c:93
 __wake_up_common_lock kernel/sched/wait.c:123 [inline]
 __wake_up_sync_key+0x83/0xc0 kernel/sched/wait.c:190
 sock_def_readable+0x61/0xe0 net/core/sock.c:2909
 tcp_data_ready net/ipv4/tcp_input.c:4795 [inline]
 tcp_rcv_established+0x13c0/0x1520 net/ipv4/tcp_input.c:5724
 tcp_v4_do_rcv+0x25e/0x480 net/ipv4/tcp_ipv4.c:1641
 tcp_v4_rcv+0x219b/0x2420 net/ipv4/tcp_ipv4.c:2023
 ip_protocol_deliver_rcu+0x1f9/0x400 net/ipv4/ip_input.c:204
 ip_local_deliver_finish net/ipv4/ip_input.c:231 [inline]
 NF_HOOK include/linux/netfilter.h:307 [inline]
 ip_local_deliver+0x1d6/0x2a0 net/ipv4/ip_input.c:252
 dst_input include/net/dst.h:449 [inline]
 ip_sublist_rcv_finish net/ipv4/ip_input.c:550 [inline]
 ip_list_rcv_finish net/ipv4/ip_input.c:600 [inline]
 ip_sublist_rcv+0x4d4/0x5a0 net/ipv4/ip_input.c:608
 ip_list_rcv+0x262/0x290 net/ipv4/ip_input.c:643
 __netif_receive_skb_list_ptype net/core/dev.c:5324 [inline]
 __netif_receive_skb_list_core+0x34b/0x450 net/core/dev.c:5372
 __netif_receive_skb_list+0x298/0x310 net/core/dev.c:5424
 netif_receive_skb_list_internal+0xda/0x330 net/core/dev.c:5531
 gro_normal_list net/core/dev.c:5642 [inline]
 gro_normal_one net/core/dev.c:5654 [inline]
 napi_skb_finish net/core/dev.c:5982 [inline]
 napi_gro_receive+0x329/0x5a0 net/core/dev.c:6014
 receive_buf+0x7a4/0xcf0 drivers/net/virtio_net.c:1082
 virtnet_receive drivers/net/virtio_net.c:1346 [inline]
 virtnet_poll+0x2fa/0x780 drivers/net/virtio_net.c:1451
 napi_poll+0x178/0x4a0 net/core/dev.c:6684
 net_rx_action+0x1ba/0x530 net/core/dev.c:6752
 __do_softirq+0x198/0x360 kernel/softirq.c:292
 asm_call_on_stack+0xf/0x20 arch/x86/entry/entry_64.S:711
 __run_on_irqstack arch/x86/include/asm/irq_stack.h:22 [inline]
 run_on_irqstack_cond arch/x86/include/asm/irq_stack.h:48 [inline]
 do_softirq_own_stack+0x5d/0x80 arch/x86/kernel/irq_64.c:77
 do_softirq+0x86/0xb0 kernel/softirq.c:337
 __local_bh_enable_ip+0x63/0x70 kernel/softirq.c:189
 local_bh_enable+0x1b/0x20 include/linux/bottom_half.h:32
 rcu_read_unlock_bh include/linux/rcupdate.h:723 [inline]
 ip_finish_output2+0x70e/0xb60 net/ipv4/ip_output.c:229
 __ip_finish_output+0x395/0x3e0 net/ipv4/ip_output.c:306
 ip_finish_output+0x39/0x160 net/ipv4/ip_output.c:316
 NF_HOOK_COND include/linux/netfilter.h:296 [inline]
 ip_output+0xf6/0x1a0 net/ipv4/ip_output.c:430
 dst_output include/net/dst.h:443 [inline]
 ip_local_out net/ipv4/ip_output.c:125 [inline]
 __ip_queue_xmit+0x9b3/0x9e0 net/ipv4/ip_output.c:530
 ip_queue_xmit include/net/ip.h:237 [inline]
 l2tp_ip_sendmsg+0x776/0x7a0 net/l2tp/l2tp_ip.c:508
 inet_sendmsg+0x5f/0x80 net/ipv4/af_inet.c:814
 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_sendmmsg+0x322/0x4b0 net/socket.c:2496
 __do_sys_sendmmsg net/socket.c:2525 [inline]
 __se_sys_sendmmsg net/socket.c:2522 [inline]
 __x64_sys_sendmmsg+0x53/0x60 net/socket.c:2522
 do_syscall_64+0x51/0xb0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff888120d80b90 of 8 bytes by task 8629 on cpu 0:
 list_empty_careful include/linux/list.h:300 [inline]
 ep_events_available fs/eventpoll.c:379 [inline]
 ep_poll fs/eventpoll.c:1855 [inline]
 do_epoll_wait+0x2e2/0x870 fs/eventpoll.c:2333
 __do_sys_epoll_pwait fs/eventpoll.c:2364 [inline]
 __se_sys_epoll_pwait fs/eventpoll.c:2350 [inline]
 __x64_sys_epoll_pwait+0x92/0x150 fs/eventpoll.c:2350
 do_syscall_64+0x51/0xb0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 8629 Comm: syz-fuzzer Not tainted 5.8.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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