The patch below does not apply to the 5.10-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From d434ab6db524ab1efd0afad4ffa1ee65ca6ac097 Mon Sep 17 00:00:00 2001

From: Pavel Begunkov asml.silence@gmail.com Date: Mon, 11 Jan 2021 04:00:30 +0000 Subject: [PATCH] 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

diff --git a/fs/io_uring.c b/fs/io_uring.c index 2f305c097bd5..7af74c1ec909 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -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();