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BUG: KCSAN: data-race in __io_cqring_fill_event / io_uring_poll

write to 0xffff88813095f480 of 4 bytes by task 5741 on cpu 1:
 io_get_cqring fs/io_uring.c:1377 [inline]
 __io_cqring_fill_event+0xfd/0x350 fs/io_uring.c:1559
 io_req_complete_post+0x58/0x540 fs/io_uring.c:1583
 io_req_complete_failed fs/io_uring.c:1650 [inline]
 __io_queue_sqe+0x340/0x360 fs/io_uring.c:6440
 io_queue_sqe fs/io_uring.c:6462 [inline]
 io_submit_sqe+0x18b8/0x33a0 fs/io_uring.c:6625
 io_submit_sqes+0x5bd/0xbd0 fs/io_uring.c:6733
 __do_sys_io_uring_enter fs/io_uring.c:9318 [inline]
 __se_sys_io_uring_enter+0x1e1/0xa80 fs/io_uring.c:9260
 __x64_sys_io_uring_enter+0x74/0x80 fs/io_uring.c:9260
 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff88813095f480 of 4 bytes by task 5736 on cpu 0:
 __io_cqring_events fs/io_uring.c:1361 [inline]
 io_cqring_events fs/io_uring.c:2199 [inline]
 io_uring_poll+0xcf/0x160 fs/io_uring.c:8661
 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+0x622/0xc40 fs/select.c:1011
 __do_sys_poll fs/select.c:1076 [inline]
 __se_sys_poll+0xce/0x1e0 fs/select.c:1064
 __x64_sys_poll+0x3f/0x50 fs/select.c:1064
 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 5736 Comm: syz-executor.3 Not tainted 5.12.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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