linux-kernel - [PATCH 5.10 054/152] io_uring: drop mm and files after task_work

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Message-Id: <20210118113355.385620010@linuxfoundation.org>
Date:   Mon, 18 Jan 2021 12:33:49 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Pavel Begunkov <asml.silence@...il.com>,
        Jens Axboe <axboe@...nel.dk>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.10 054/152] io_uring: drop mm and files after task_work_run

From: Pavel Begunkov <asml.silence@...il.com>

[ Upstream commit d434ab6db524ab1efd0afad4ffa1ee65ca6ac097 ]

__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@...r.kernel.org # 5.9+
Signed-off-by: Pavel Begunkov <asml.silence@...il.com>
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/io_uring.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 6c356b9e87b39..cab640c10bc0f 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -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();
-- 
2.27.0