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BUG: KCSAN: data-race in __io_cqring_fill_event / io_drain_req

write to 0xffff888130823400 of 4 bytes by task 4474 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+0x338a/0x6870 fs/io_uring.c:3622
 io_wq_submit_work+0x113/0x1f0 fs/io_uring.c:6260
 io_worker_handle_work+0x8cb/0xaf0 fs/io-wq.c:496
 io_wqe_worker+0x184/0x4b0 fs/io-wq.c:545
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

read to 0xffff888130823400 of 4 bytes by task 4472 on cpu 1:
 req_need_defer fs/io_uring.c:1232 [inline]
 io_drain_req+0x4da/0x630 fs/io_uring.c:6017
 io_queue_sqe fs/io_uring.c:6462 [inline]
 io_submit_sqe+0x2e66/0x3400 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

value changed: 0x00000000 -> 0x00000001

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 4472 Comm: syz-executor.2 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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