io_uring: don't leak creds on SQO attach error

Attaching to already dead/dying SQPOLL task is disallowed in
io_sq_offload_create(), but cleanup is hand coded by calling
io_put_sq_data()/etc., that miss to put ctx->sq_creds.

Defer everything to error-path io_sq_thread_finish(), adding
ctx->sqd_list in the error case as well as finish will handle it.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

fs/io_uring.c

@@ -7910,22 +7910,17 @@ static int io_sq_offload_create(struct io_ring_ctx *ctx,
 
 		ret = 0;
 		io_sq_thread_park(sqd);
-		/* don't attach to a dying SQPOLL thread, would be racy */
-		if (attached && !sqd->thread) {
-			ret = -ENXIO;
-		} else {
 		list_add(&ctx->sqd_list, &sqd->ctx_list);
 		io_sqd_update_thread_idle(sqd);
-		}
+		/* don't attach to a dying SQPOLL thread, would be racy */
+		if (attached && !sqd->thread)
+			ret = -ENXIO;
 		io_sq_thread_unpark(sqd);
 
-		if (ret < 0) {
-			io_put_sq_data(sqd);
-			ctx->sq_data = NULL;
-			return ret;
-		} else if (attached) {
+		if (ret < 0)
+			goto err;
+		if (attached)
 			return 0;
-		}
 
 		if (p->flags & IORING_SETUP_SQ_AFF) {
 			int cpu = p->sq_thread_cpu;