AZL-68111

In the Linux kernel, the following vulnerability has been resolved:

iouring/io-wq: Use setbit() and test_bit() at worker->flags

Utilize setbit() and testbit() on worker->flags within io_uring/io-wq to address potential data races.

The structure ioworker->flags may be accessed through various data paths, leading to concurrency issues. When KCSAN is enabled, it reveals data races occurring in ioworkerhandlework and iowqactivatefreeworker functions.

 BUG: KCSAN: data-race in io_worker_handle_work / io_wq_activate_free_worker
 write to 0xffff8885c4246404 of 4 bytes by task 49071 on cpu 28:
 io_worker_handle_work (io_uring/io-wq.c:434 io_uring/io-wq.c:569)
 io_wq_worker (io_uring/io-wq.c:?)

<snip>

 read to 0xffff8885c4246404 of 4 bytes by task 49024 on cpu 5:
 io_wq_activate_free_worker (io_uring/io-wq.c:? io_uring/io-wq.c:285)
 io_wq_enqueue (io_uring/io-wq.c:947)
 io_queue_iowq (io_uring/io_uring.c:524)
 io_req_task_submit (io_uring/io_uring.c:1511)
 io_handle_tw_list (io_uring/io_uring.c:1198)

<snip>

Line numbers against commit 18daea77cca6 ("Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm").

These races involve writes and reads to the same memory location by different tasks running on different CPUs. To mitigate this, refactor the code to use atomic operations such as setbit(), testbit(), and clear_bit() instead of basic "and" and "or" operations. This ensures thread-safe manipulation of worker flags.

Also, move create_index to avoid holes in the structure.