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

Commit 3539b14 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: axboe

io_uring/io_uring.c

@@ -1248,8 +1248,10 @@ static void io_req_task_cancel(struct io_kiocb *req, bool *locked)
 
 void io_req_task_submit(struct io_kiocb *req, bool *locked)
 {
-	io_tw_lock(req->ctx, locked);
-	if (likely(!io_should_terminate_tw()))
+	struct io_ring_ctx *ctx = req->ctx;
+
+	io_tw_lock(ctx, locked);
+	if (likely(!io_should_terminate_tw(ctx)))
 		io_queue_sqe(req);
 	else
 		io_req_complete_failed(req, -EFAULT);
@@ -1771,8 +1773,10 @@ static int io_issue_sqe(struct io_kiocb *req, unsigned int issue_flags)
 
 int io_poll_issue(struct io_kiocb *req, bool *locked)
 {
-	io_tw_lock(req->ctx, locked);
-	if (unlikely(io_should_terminate_tw()))
+	struct io_ring_ctx *ctx = req->ctx;
+
+	io_tw_lock(ctx, locked);
+	if (unlikely(io_should_terminate_tw(ctx)))
 		return -EFAULT;
 	return io_issue_sqe(req, IO_URING_F_NONBLOCK|IO_URING_F_MULTISHOT);
 }

io_uring/io_uring.h

@@ -403,9 +403,9 @@ 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

@@ -241,7 +241,7 @@ static int io_poll_check_events(struct io_kiocb *req, bool *locked)
 	struct io_ring_ctx *ctx = req->ctx;
 	int v;
 
-	if (unlikely(io_should_terminate_tw()))
+	if (unlikely(io_should_terminate_tw(ctx)))
 		return -ECANCELED;
 
 	do {

io_uring/timeout.c

@@ -275,7 +275,7 @@ static void io_req_task_link_timeout(struct io_kiocb *req, bool *locked)
 	int ret = -ENOENT;
 
 	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,