[PATCH 5.10 053/152] io_uring: dont take files/mm for a dead task

[Greg Kroah-Hartman]

From: Pavel Begunkov <asml.silence@xxxxxxxxx>

[ Upstream commit 621fadc22365f3cf307bcd9048e3372e9ee9cdcc ]

In rare cases a task may be exiting while io_ring_exit_work() trying to
cancel/wait its requests. It's ok for __io_sq_thread_acquire_mm()
because of SQPOLL check, but is not for __io_sq_thread_acquire_files().
Play safe and fail for both of them.

Cc: stable@xxxxxxxxxxxxxxx # 5.5+
Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 fs/io_uring.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 4833b68f1a1cc..6c356b9e87b39 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1009,6 +1009,8 @@ static int __io_sq_thread_acquire_mm(struct io_ring_ctx *ctx)
 {
 	struct mm_struct *mm;
 
+	if (current->flags & PF_EXITING)
+		return -EFAULT;
 	if (current->mm)
 		return 0;
 
-- 
2.27.0