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BUG: KCSAN: data-race in do_epoll_wait / ep_poll_callback

write to 0xffff888100bf83e8 of 4 bytes by task 6525 on cpu 0:
 ep_send_events fs/eventpoll.c:1698 [inline]
 ep_poll fs/eventpoll.c:1798 [inline]
 do_epoll_wait+0x843/0xf00 fs/eventpoll.c:2226
 __do_sys_epoll_wait fs/eventpoll.c:2238 [inline]
 __se_sys_epoll_wait fs/eventpoll.c:2233 [inline]
 __x64_sys_epoll_wait+0xf6/0x120 fs/eventpoll.c:2233
 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff888100bf83e8 of 4 bytes by task 6544 on cpu 1:
 ep_poll_callback+0x40b/0x4e0 fs/eventpoll.c:1206
 __wake_up_common+0xbc/0x130 kernel/sched/wait.c:108
 __wake_up_common_lock kernel/sched/wait.c:138 [inline]
 __wake_up+0x80/0xc0 kernel/sched/wait.c:157
 sock_def_wakeup+0x54/0x70 net/core/sock.c:2895
 inet_shutdown+0x1e4/0x200 net/ipv4/af_inet.c:911
 __sys_shutdown_sock net/socket.c:2189 [inline]
 __sys_shutdown net/socket.c:2201 [inline]
 __do_sys_shutdown net/socket.c:2209 [inline]
 __se_sys_shutdown+0xf6/0x140 net/socket.c:2207
 __x64_sys_shutdown+0x2d/0x40 net/socket.c:2207
 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x4000201b -> 0x40000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 6544 Comm: syz-executor.5 Not tainted 5.13.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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