io_uring: include dying ring in task_work "should cancel" state

When running task_work for an exiting task, rather than perform the
issue retry attempt, the task_work is canceled. However, this isn't
done for a ring that has been closed. This can lead to requests being
successfully completed post the ring being closed, which is somewhat
confusing and surprising to an application.

Rather than just check the task exit state, also include the ring
ref state in deciding whether or not to terminate a given request when
run from task_work.

Cc: stable@vger.kernel.org # 6.1+
Link: axboe/liburing#1459
Reported-by: Benedek Thaler <thaler@thaler.hu>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: axboe

io_uring/io_uring.c

@@ -1406,8 +1406,10 @@ static void io_req_task_cancel(struct io_kiocb *req, io_tw_token_t tw)
 
 void io_req_task_submit(struct io_kiocb *req, io_tw_token_t tw)
 {
-	io_tw_lock(req->ctx, tw);
-	if (unlikely(io_should_terminate_tw()))
+	struct io_ring_ctx *ctx = req->ctx;
+
+	io_tw_lock(ctx, tw);
+	if (unlikely(io_should_terminate_tw(ctx)))
 		io_req_defer_failed(req, -EFAULT);
 	else if (req->flags & REQ_F_FORCE_ASYNC)
 		io_queue_iowq(req);

io_uring/io_uring.h

@@ -476,9 +476,9 @@ static inline bool io_allowed_run_tw(struct io_ring_ctx *ctx)
  * 2) PF_KTHREAD is set, in which case the invoker of the task_work is
  *    our fallback task_work.
  */
-static inline bool io_should_terminate_tw(void)
+static inline bool io_should_terminate_tw(struct io_ring_ctx *ctx)
 {
-	return current->flags & (PF_KTHREAD | PF_EXITING);
+	return (current->flags & (PF_KTHREAD | PF_EXITING)) || percpu_ref_is_dying(&ctx->refs);
 }
 
 static inline void io_req_queue_tw_complete(struct io_kiocb *req, s32 res)

io_uring/poll.c

@@ -224,7 +224,7 @@ static int io_poll_check_events(struct io_kiocb *req, io_tw_token_t tw)
 {
 	int v;
 
-	if (unlikely(io_should_terminate_tw()))
+	if (unlikely(io_should_terminate_tw(req->ctx)))
 		return -ECANCELED;
 
 	do {

io_uring/timeout.c

@@ -324,7 +324,7 @@ static void io_req_task_link_timeout(struct io_kiocb *req, io_tw_token_t tw)
 	int ret;
 
 	if (prev) {
-		if (!io_should_terminate_tw()) {
+		if (!io_should_terminate_tw(req->ctx)) {
 			struct io_cancel_data cd = {
 				.ctx		= req->ctx,
 				.data		= prev->cqe.user_data,

io_uring/uring_cmd.c

@@ -118,7 +118,7 @@ static void io_uring_cmd_work(struct io_kiocb *req, io_tw_token_t tw)
 	struct io_uring_cmd *ioucmd = io_kiocb_to_cmd(req, struct io_uring_cmd);
 	unsigned int flags = IO_URING_F_COMPLETE_DEFER;
 
-	if (io_should_terminate_tw())
+	if (io_should_terminate_tw(req->ctx))
 		flags |= IO_URING_F_TASK_DEAD;
 
 	/* task_work executor checks the deffered list completion */