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BUG: KCSAN: data-race in do_epoll_wait / ep_poll_callback

write to 0xffff888100e20a68 of 4 bytes by task 29498 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_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff888100e20a68 of 4 bytes by task 29509 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
 tty_ldisc_lock drivers/tty/tty_ldisc.c:322 [inline]
 tty_ldisc_hangup+0x1ae/0x470 drivers/tty/tty_ldisc.c:738
 __tty_hangup+0x49c/0x650 drivers/tty/tty_io.c:639
 tty_vhangup+0x13/0x20 drivers/tty/tty_io.c:711
 pty_close+0x27b/0x2a0 drivers/tty/pty.c:79
 tty_release+0x255/0xa10 drivers/tty/tty_io.c:1771
 __fput+0x295/0x520 fs/file_table.c:280
 ____fput+0x11/0x20 fs/file_table.c:313
 task_work_run+0xae/0x130 kernel/task_work.c:164
 tracehook_notify_resume include/linux/tracehook.h:189 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:175 [inline]
 exit_to_user_mode_prepare+0x156/0x190 kernel/entry/common.c:209
 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
 syscall_exit_to_user_mode+0x20/0x40 kernel/entry/common.c:302
 do_syscall_64+0x49/0x90 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x40002019 -> 0x40000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 29509 Comm: syz-executor.4 Not tainted 5.14.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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