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io_uring: drop mm and files after task_work_run

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[ Upstream commit d434ab6db5 ]

__io_req_task_submit() run by task_work can set mm and files, but
io_sq_thread() in some cases, and because __io_sq_thread_acquire_mm()
and __io_sq_thread_acquire_files() do a simple current->mm/files check
it may end up submitting IO with mm/files of another task.

We also need to drop it after in the end to drop potentially grabbed
references to them.

Cc: stable@vger.kernel.org # 5.9+
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Pavel Begunkov 2021-01-11 04:00:30 +00:00 committed by Greg Kroah-Hartman
parent a3647cddfe
commit f7f32822a4
1 changed files with 2 additions and 0 deletions
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2
fs/io_uring.c
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@ -6841,6 +6841,7 @@ static int io_sq_thread(void *data)
if (ret & SQT_SPIN) {
io_run_task_work();
io_sq_thread_drop_mm();
cond_resched();
} else if (ret == SQT_IDLE) {
if (kthread_should_park())
@ -6855,6 +6856,7 @@ static int io_sq_thread(void *data)
}
io_run_task_work();
io_sq_thread_drop_mm();
if (cur_css)
io_sq_thread_unassociate_blkcg();