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BUG: KCSAN: data-race in __io_cqring_fill_event / io_req_defer

write to 0xffff88812b84e440 of 4 bytes by task 10605 on cpu 0:
 io_get_cqring fs/io_uring.c:1352 [inline]
 __io_cqring_fill_event+0x135/0x400 fs/io_uring.c:1491
 io_req_complete_post+0x49/0x570 fs/io_uring.c:1531
 __io_req_complete fs/io_uring.c:1579 [inline]
 __io_complete_rw+0x3a0/0x430 fs/io_uring.c:2522
 io_complete_rw+0x1b/0x20 fs/io_uring.c:2529
 io_rw_done fs/io_uring.c:2756 [inline]
 kiocb_done+0x1d3/0x8d0 fs/io_uring.c:2780
 io_write fs/io_uring.c:3453 [inline]
 io_issue_sqe+0x27c8/0x6080 fs/io_uring.c:6061
 io_wq_submit_work+0x112/0x300 fs/io_uring.c:6193
 io_worker_handle_work+0xbbb/0xe20 fs/io-wq.c:451
 io_wqe_worker+0x1e5/0x580 fs/io-wq.c:501
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

read to 0xffff88812b84e440 of 4 bytes by task 10602 on cpu 1:
 req_need_defer fs/io_uring.c:1185 [inline]
 io_req_defer+0x344/0x470 fs/io_uring.c:5954
 io_queue_sqe+0x18/0x160 fs/io_uring.c:6361
 io_submit_sqe+0x15c7/0x30c0 fs/io_uring.c:6546
 io_submit_sqes+0x61f/0xaf0 fs/io_uring.c:6660
 __do_sys_io_uring_enter fs/io_uring.c:9240 [inline]
 __se_sys_io_uring_enter+0x217/0xb20 fs/io_uring.c:9182
 __x64_sys_io_uring_enter+0x74/0x80 fs/io_uring.c:9182
 do_syscall_64+0x34/0x50 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 10602 Comm: syz-executor.5 Tainted: G        W         5.12.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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