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BUG: KCSAN: data-race in __io_cqring_fill_event / io_uring_poll

write to 0xffff88813b114c00 of 4 bytes by task 18759 on cpu 0:
 io_get_cqe fs/io_uring.c:1580 [inline]
 __io_cqring_fill_event+0xfb/0x350 fs/io_uring.c:1765
 io_submit_flush_completions+0xc1/0x440 fs/io_uring.c:2315
 __io_queue_sqe+0x2bc/0x460 fs/io_uring.c:6877
 io_queue_sqe fs/io_uring.c:6915 [inline]
 io_submit_sqe+0x88b/0x3e80 fs/io_uring.c:7091
 io_submit_sqes+0x505/0xde0 fs/io_uring.c:7197
 __do_sys_io_uring_enter fs/io_uring.c:9839 [inline]
 __se_sys_io_uring_enter+0x213/0xae0 fs/io_uring.c:9781
 __x64_sys_io_uring_enter+0x74/0x80 fs/io_uring.c:9781
 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 0xffff88813b114c00 of 4 bytes by task 18742 on cpu 1:
 __io_cqring_events fs/io_uring.c:1564 [inline]
 io_cqring_events fs/io_uring.c:2367 [inline]
 io_uring_poll+0xc6/0x150 fs/io_uring.c:9185
 vfs_poll include/linux/poll.h:90 [inline]
 do_pollfd fs/select.c:869 [inline]
 do_poll fs/select.c:917 [inline]
 do_sys_poll+0x622/0xc00 fs/select.c:1011
 __do_sys_ppoll fs/select.c:1117 [inline]
 __se_sys_ppoll+0x169/0x1b0 fs/select.c:1097
 __x64_sys_ppoll+0x63/0x70 fs/select.c:1097
 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: 0x000003e0 -> 0x00000400

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 18742 Comm: syz-executor.0 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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