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@xxxxxxxxxxxxxxx>.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
>From d434ab6db524ab1efd0afad4ffa1ee65ca6ac097 Mon Sep 17 00:00:00 2001
From: Pavel Begunkov <asml.silence@xxxxxxxxx>
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@xxxxxxxxxxxxxxx # 5.9+
Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
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();
