[PATCH 5.15 094/171] io_uring: ensure task_work gets run as part of cancelations

Greg Kroah-Hartman
2021-12-13T10:24:33Z

From: Jens Axboe <axboe@kernel.dk>

commit 78a780602075d8b00c98070fa26e389b3b3efa72 upstream.

If we successfully cancel a work item but that work item needs to be
processed through task_work, then we can be sleeping uninterruptibly
in io_uring_cancel_generic() and never process it. Hence we don't
make forward progress and we end up with an uninterruptible sleep
warning.

While in there, correct a comment that should be IFF, not IIF.

Reported-and-tested-by: syzbot+21e6887c0be14181206d@syzkaller.appspotmail.com
Cc: stable@vger.kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/io_uring.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -9775,7 +9775,7 @@ static void io_uring_drop_tctx_refs(stru

/*
* Find any io_uring ctx that this task has registered or done IO on, and cancel
- * requests. @sqd should be not-null IIF it's an SQPOLL thread cancellation.
+ * requests. @sqd should be not-null IFF it's an SQPOLL thread cancellation.
*/
static void io_uring_cancel_generic(bool cancel_all, struct io_sq_data *sqd)
{
@@ -9816,8 +9816,10 @@ static void io_uring_cancel_generic(bool
cancel_all);
}

- prepare_to_wait(&tctx->wait, &wait, TASK_UNINTERRUPTIBLE);
+ prepare_to_wait(&tctx->wait, &wait, TASK_INTERRUPTIBLE);
+ io_run_task_work();
io_uring_drop_tctx_refs(current);
+
/*
* If we've seen completions, retry without waiting. This
* avoids a race where a completion comes in before we did