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

io_uring/io-wq: re-check IO_WQ_BIT_EXIT for each linked work item

commit 10dc95939817 ("io_uring/io-wq: check IO_WQ_BIT_EXIT inside work
run loop") fixed the obvious case where io_worker_handle_work() took one
exit-bit snapshot before draining pending work, but the fix stops one
level too early.

io_worker_handle_work() now re-checks IO_WQ_BIT_EXIT in its outer work
run loop, yet it still snapshots that bit once before processing a whole
dependent linked-work chain. If io_wq_exit_start() sets IO_WQ_BIT_EXIT
after the first linked item has started, the remaining linked items can
still reuse stale do_kill = false, skip IO_WQ_WORK_CANCEL, and continue
running after exit has begun.

Move the check further inside, so it covers linked items too. Note: this
is a syzbot special as it loves setting up tons of slow linked work on
weird devices like msr that take forever to read, and immediately close
the ring. Exit then takes a long time.

https://git.kernel.org/stable/c/14b7ecad2ec56699325180a744f4b19f046401bb

https://git.kernel.org/stable/c/1636d85dc139b07c0449308f2bb5e0c7a2e0da99

https://git.kernel.org/stable/c/29bef9934b2521f787bb15dd1985d4c0d12ae02a

https://git.kernel.org/stable/c/6e2f51f3e06773c2ee98ad09738f0908b48f76f9

https://git.kernel.org/stable/c/ab85765cbe3258b43dc6729af0e6ce3a87a133d8

https://git.kernel.org/stable/c/b6f179a653a934736c88d820fe0098c3c2532549

https://git.kernel.org/stable/c/d179533c610e1b4c6aa436e3c1fd1b719d2c727c

https://git.kernel.org/stable/c/ea61b04e1d7242cb37f5ed2cc91cf21a493f6597

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