io_uring: defer foreign io-wq enqueues to task_work

An IOPOLL ring without DEFER_TASKRUN can be reaped by a task other than
the one that submitted the I/O. If a polled request is marked
REQ_F_REISSUE, io_free_batch_list() calls io_queue_iowq() with the
original tctx. Ordinary task exit can tear down tctx->io_wq after
draining only the tracked requests. The live request pins the task, but
not its io-wq, so the foreign task can race io_wq_put_and_exit() and
enqueue through a freed or NULL queue.

Forward foreign userspace enqueues to the owning task before accessing
tctx->io_wq. Use a dedicated task_work callback so reissues still go
straight to io-wq, and fail them if task_work is running in cancellation
mode. Preserve the existing PF_KTHREAD cancellation path. This also
covers the other callers of io_queue_iowq() without changing the
worker-owned enqueue path.

Signed-off-by: Kyle Zeng <kylebot@openai.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

0 files changed, 0 insertions, 0 deletions