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BUG: KCSAN: data-race in __io_cqring_fill_event / io_uring_poll

write to 0xffff888108169c00 of 4 bytes by task 12952 on cpu 0:
 io_get_cqe fs/io_uring.c:1403 [inline]
 __io_cqring_fill_event+0xfb/0x350 fs/io_uring.c:1582
 io_req_complete_post+0x55/0x5c0 fs/io_uring.c:1606
 io_issue_sqe+0x41b6/0x6870 fs/io_uring.c:4240
 __io_queue_sqe+0xe7/0x360 fs/io_uring.c:6423
 io_queue_sqe fs/io_uring.c:6466 [inline]
 io_submit_sqe+0x1695/0x3400 fs/io_uring.c:6621
 io_submit_sqes+0x822/0xe50 fs/io_uring.c:6737
 __do_sys_io_uring_enter fs/io_uring.c:9342 [inline]
 __se_sys_io_uring_enter+0x1c7/0xa10 fs/io_uring.c:9285
 __x64_sys_io_uring_enter+0x74/0x80 fs/io_uring.c:9285
 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 0xffff888108169c00 of 4 bytes by task 12951 on cpu 1:
 __io_cqring_events fs/io_uring.c:1387 [inline]
 io_cqring_events fs/io_uring.c:2163 [inline]
 io_uring_poll+0xc6/0x150 fs/io_uring.c:8697
 vfs_poll include/linux/poll.h:90 [inline]
 io_poll_rewait fs/io_uring.c:4843 [inline]
 io_poll_task_func+0x113/0x690 fs/io_uring.c:4921
 tctx_task_work+0x1b8/0x420 fs/io_uring.c:1938
 task_work_run+0xae/0x130 kernel/task_work.c:164
 io_run_task_work fs/io_uring.c:2197 [inline]
 io_run_task_work_sig fs/io_uring.c:6964 [inline]
 io_cqring_wait_schedule fs/io_uring.c:6981 [inline]
 io_cqring_wait+0x437/0x7d0 fs/io_uring.c:7052
 __do_sys_io_uring_enter fs/io_uring.c:9368 [inline]
 __se_sys_io_uring_enter+0x5ea/0xa10 fs/io_uring.c:9285
 __x64_sys_io_uring_enter+0x74/0x80 fs/io_uring.c:9285
 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

value changed: 0x00000144 -> 0x0000014a

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 12951 Comm: syz-executor.3 Not tainted 5.14.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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