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BUG: KCSAN: data-race in __io_cqring_fill_event / io_drain_req

write to 0xffff88812929ec00 of 4 bytes by task 6367 on cpu 0:
 io_get_cqe fs/io_uring.c:1424 [inline]
 __io_cqring_fill_event+0xfb/0x350 fs/io_uring.c:1606
 io_req_complete_post+0x55/0x5c0 fs/io_uring.c:1630
 __io_req_complete fs/io_uring.c:1682 [inline]
 __io_complete_rw+0x3e1/0x4a0 fs/io_uring.c:2501
 io_complete_rw+0x1b/0x20 fs/io_uring.c:2508
 io_rw_done fs/io_uring.c:2760 [inline]
 kiocb_done+0x18a/0x3f0 fs/io_uring.c:2784
 io_read fs/io_uring.c:3365 [inline]
 io_issue_sqe+0x3108/0x64b0 fs/io_uring.c:6180
 io_wq_submit_work+0x113/0x1f0 fs/io_uring.c:6305
 io_worker_handle_work+0x8cb/0xaf0 fs/io-wq.c:525
 io_wqe_worker+0x184/0x4b0 fs/io-wq.c:574
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

read to 0xffff88812929ec00 of 4 bytes by task 6366 on cpu 1:
 req_need_defer fs/io_uring.c:1233 [inline]
 io_drain_req+0x4da/0x630 fs/io_uring.c:6062
 io_queue_sqe fs/io_uring.c:6507 [inline]
 io_submit_sqe+0x2e66/0x3400 fs/io_uring.c:6666
 io_submit_sqes+0x822/0xe50 fs/io_uring.c:6782
 __do_sys_io_uring_enter fs/io_uring.c:9389 [inline]
 __se_sys_io_uring_enter+0x20c/0xb20 fs/io_uring.c:9332
 __x64_sys_io_uring_enter+0x74/0x80 fs/io_uring.c:9332
 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: 6366 Comm: syz-executor.3 Tainted: G        W         5.14.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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