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io_uring: drop mm and files after task_work_run 

__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>
This commit is contained in:
Pavel Begunkov 2021-01-11 04:00:30 +00:00 committed by Jens Axboe
parent d9d05217cb
commit d434ab6db5
1 changed files with 2 additions and 0 deletions
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2
fs/io_uring.c
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@ -7056,6 +7056,7 @@ static int io_sq_thread(void *data)
if (sqt_spin || !time_after(jiffies, timeout)) {
io_run_task_work();
io_sq_thread_drop_mm_files();
cond_resched();
if (sqt_spin)
timeout = jiffies + sqd->sq_thread_idle;
@ -7093,6 +7094,7 @@ static int io_sq_thread(void *data)
}
io_run_task_work();
io_sq_thread_drop_mm_files();
if (cur_css)
io_sq_thread_unassociate_blkcg();